Sky and Telescope

THE ESSENTIAL MAGAZINE OF ASTRONOMY

ISSUE 82

TRAVEL GUIDE: The Next 3 Solar Eclipses p.70

10TH BIRTHDAY ISSUE!

AS&T TEST REPORT: A Versatile Solar Filter p.44

The Exquisite Shells of Dying Starsp.22

A New Look at Mercury p.18

Bizarre Alien Weather p.32

Explore Summer Galaxies p.64

HOW TO: Remove Imaging Artefacts p.78

4 AUSTRALIAN SKY & TELESCOPE JANUARY 2015

8 Spectrum Celebrating 10 Years of AS&T By Greg Bryant

10 News Notes• OrbitersReachMars• SurprisingBlackHole• HomeSupercluster• andmore…

13 10 & 5 Years Ago By Greg Bryant

14 Countdown to Pluto By Greg Bryant

16 Discoveries The Growing Universe By David Ellyard

18 New Mercury Map MeettheplanetnearestourSun.

January 2015 Vol. 11, No. 1

ContentsNEWS & FEATURES

Cover Story

AS&T TEST REPORT

44 The Quark from DayStar Filters Anewapproachtoaffordablesolarhydrogen-filters.By Sean Walker

48 New Product Showcase

49 In This Section

50 Binocular Highlight Andromeda’sNGC752 By Gary Seronik

52 Tonight’s Sky The Celestial Twins By Greg Bryant

54 Sun, Moon, and Planets JupiterNearsOpposition By Greg Bryant

OBSERVING & EXPLORING

22 Spider Webs in Space Astronomersarestillpuzzledbyhowstarscreatethebizarrevarietyofplanetarynebulaeinourgalaxy. By Robert Zimmerman

32 Weird Weather on Alien Worlds Astronomershavegonebeyondmerelycountingexoplanetstostudyingtheiratmospheres. By Jonathan Fortney

40 From the Moon to Distant Galaxies TheAstronomicalSocietyofAustraliarecognisesexcellenceinresearchbythenextgenerationofastronomers.By Tanya Hill

58 Celestial Calendar AnAussieCometSummer By David Seargent

59 Celestial Calendar RReticuli By Alan Plummer

60 Double Star Notes RevisitingtheGreatHunter By Ross Gould

62 Exploring The Moon HuntingforLostBasins By Charles A. Wood

64 Targets StarBound By Sue French

68 Going Deep FuzzyDuosInsidetheCirclet By Ken Hewitt-White

p.22 Mysteries of planetary nebulae

p.86 Australian astrophotography

www.skyandtelescope.com.au 5

70 A Trio of Total Solar Eclipses The next three years each offer a

chance to view one of nature’s greatest spectacles.

By Fred Espenak & Jay Anderson

76 Telescope Workshop No-Tools Collimation By Gary Seronik

78 Eliminating Band & Line Noise Here’s a technique that removes common artefacts from DSLR and CCD images.

By Michael Unsold

82 A Star Walk for Everyone This project aims to protect the night

sky by turning people’s eyes to the stars.

By Karoline Mrazek & Erwin Matys

67 Subscription Offer Subscribe and receive a 2015

Astronomy Calendar or Yearbook!

AUSTRALIAN SKY & TELESCOPE (ISSN 1832-0457) is published 8 times per year by Odysseus Publishing Pty Limited, PO Box 81, St Leonards, NSW, 1590. Phone (02) 9439 1955, fax (02) 9439 1977. © 2014 Odysseus Publishing Pty Limited. All rights reserved.

ON THE COVER: NGC 6302’s wings are one example of the mysterious shapes of planetary nebulae. NASA / ESA / HUBBLE SM4 ERO TEAM

THE ASTRONOMY SCENE

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86 Gallery — The 2014 David Malin Awards

97 Index to Advertisers

97 Manufacturer and Dealer Directory

98 Focal Point Winning Converts to the Cause By Bert Probst

64

44

p.32 Strange weather on alien worlds

p.40 Australian astronomy in the spotlight

p.70 Start planning to see a solar eclipse

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Greg BryantSpectrum

EDITORIALEDITOR Greg Bryant

DESIGN Simone MarinkovicCONTRIBUTING EDITORS

John Drummond, David Ellyard,Ross Gould, Steve Kerr,

Alan Plummer, David SeargentEMAIL [email protected]

ADVERTISINGADVERTISING MANAGER Greg BryantEMAIL [email protected]

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Australia distribution by Network Services. New Zealand distribution by Gordon & Gotch. © 2014 Sky Publishing Corporation and Odysseus Publishing Pty Limited. No part of this publication may be reproduced, translated, or converted into a machine-readable form or language without the written consent of the publisher. Australian Sky & Telescope is published by Odysseus Publishing Pty Limited under licence from Sky Publishing Corporation as the Australian edition of Sky & Telescope. Australian Sky & Telescope is a registered trademark of Sky Publishing USA. Articles express the opinions of the authors and are not necessarily those of the Editor or Odysseus Publishing Pty Limited. ISSN 1832-0457


ISSUE NO 82JANUARY 2015

SKY & TELESCOPE INTERNATIONAL

EDITOR IN CHIEFPeter Tyson

EDITORIALSENIOR EDITOR

Alan M. MacRobert IMAGING EDITOR Sean Walker

SCIENCE EDITOR Camille M. CarlisleWEB EDITOR Monica Young

EQUIPMENT EDITOR John S. GianforteOBSERVING EDITOR Susan N. Johnson-

RoehrSENIOR CONTRIBUTING EDITORS

J. Kelly Beatty, Robert Naeye, Roger W. Sinnott

DESIGN DIRECTOR Patricia Gillis-CoppolaILLUSTRATION DIRECTOR Gregg

DindermanFounded in 1941 by Charles A. Federer Jr.

and Helen Spence Federer

Celebrating 10 Years of AS&T

Australian Sky & Telescope is now on Facebook. Complementing our website, Facebook helps keep you alerted to astronomy news and information about Australian Sky & Telescope. Visit www.skyandtelescope.com.au, click on the Facebook link, and become a fan today.

This issue of Australian Sky & Telescope that you’re now reading marks ten years since the magazine debuted. So much has happen in the world of astronomy and space exploration during those years. We saw the surface of

Titan for the � rst time in 2005 when the Huygens probe landed, continued to wonder at new images from Mars and Saturn, and we’ve been following the journey of New Horizons, launched in 2006, towards its encounter with Pluto (and beyond) next July.

On the subject of Pluto, its reclassi� cation from “major planet” to “dwarf planet” at the International Astronomical Union’s General Assembly in 2006, coming hot on the heels of what was initially deemed to be the discovery of the “10th Planet” in 2005, caused much controversy. With planet de� nitions being debated, it was only a couple of years later that we saw our � rst images of worlds around other stars.

Australian astronomy has continued to punch above its weight on the global stage. Part of the Square Kilometre Array (SKA) will be built here in the coming decade. Our telescopes and astronomers have continued to deliver world-class science, such as that showcased on page 40.

We’ve witnessed a Great Comet in the passage of Comet McNaught in 2007 and tens of thousands experienced the sublime beauty of a total solar eclipse in northern Australia in 2012 (photos don’t do an eclipse justice — you have to be there!).

And we celebrated the International Year of Astronomy in 2009. We’ve covered so much in the past ten years and worked hard in bringing the wonders of astronomy to more and more people. It’s � tting that this issue’s Focal Point column on page 98 draws attention to such a worthwhile mission.

On that note, this is my last issue as I’m departing as Editor of Australian Sky & Telescope.

I must thank the Odysseus Publishers Ian Brooks and Todd Cole for entrusting me with this magazine this past eight years. To the designers I’ve worked with over this time — Julitta Overdijk, Tony Temple, and Simone Marinkovic — the 6,000+ pages we’ve put together is testimony to your hard work. My friends at Sky & Telescope in the U.S. have been a source of inspiration and I must also acknowledge our advertisers and regular writers who have helped bring you this magazine. Most importantly, my family has been there too in supporting me.

It’s been an incredible journey, the “road less travelled”, and now the next chapter awaits. I look forward to seeing the astronomy community in Australia continue to grow and prosper.

Sincerely,

[email protected]

Sincerely,

[email protected]

Australian Geographic | shop.australiangeographic.com.auOzScopes | www.ozscopes.com.au

Telescopes Direct | www.telescopesdirect.com.au Optics Central | www.opticscentral.com.au

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News Notes

Orbiters Reach MarsMISSIONS I

Space around the Red Planet got more crowded in September, as two orbiters joined three already

active there. The arrivals raise the number of operating missions at Mars to a record high of seven.

First came NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. After a 10-month, 711-million-kilometre cruise that began November 18th last year, MAVEN fired its braking rockets for 33 minutes and slipped into orbit at 2:24 UT on September 22nd. Later rocket firings trimmed the spacecraft’s initial polar orbit to a 4½-hour-long loop ranging from 150 to 6,200 kilometres

above the planet’s surface.MAVEN will study the Martian

atmosphere and the charged particles, electromagnetic fields, and plasma waves racing by in the solar wind (AS&T: October 2014, p. 20). Over the next year, it will also drop five times to altitudes as low as 125 kilometres to sample the uppermost wisps of the planet’s tenuous air.

Mission scientists hope to answer a puzzle: how, when, and why did Mars evolve from its initially denser atmosphere and warmer climate to the bleak, frozen world seen today? One leading theory is that the solar

wind stripped the atmosphere away. MAVEN’s spectrometers will study whether atoms are escaping to space today and at what rate.

Two days after MAVEN, India’s Mars Orbiter Mission (MOM) arrived on the scene. Launched November 5th last year, MOM fired its braking rocket for 24¼ minutes and achieved Martian orbit on September 24th at 2:00 UT.

It was a historic day for the Indian Space Research Organisation (ISRO). MOM (informally called Mangalyaan, Hindi for “Mars-craft”) is India’s first interplanetary explorer, and never before has a spacefaring nation successfully reached Mars on its first try.

The spacecraft utilises the same basic design as ISRO’s 2008 lunar orbiter, Chandrayaan 1, a cube-shaped structure about 1½ metres on a side with a mass of 1½ tonnes. The mission’s primary objective is to show ISRO can design and operate a successful interplanetary spacecraft.

But MOM’s instrumental payload, though modest, can potentially deliver important discoveries. A colour camera will record the Martian surface. Also aboard is a Lyman-alpha photometer that will deduce the relative abundance of deuterium in the planet’s uppermost atmosphere. A spectrometer will determine the abundance of atmospheric methane — a gas at the centre of debate (AS&T: January 2014, p. 16) — down to parts-per-billion levels. Rounding out the payload are a thermal-emission spectrometer (for assessing surface composition and mechanical properties) and a mass spectrometer (for atmospheric composition).

J. KELLY BEATTY

NA

SA

/ J

PL-

CA

LTE

CH

GALAXIES I Galaxy Growth Still Mysterious


Spiral galaxy observations are shedding doubt on cosmic cannibalism’s role in building up large galaxies.

Multiple studies have suggested that galaxies don’t depend on major mergers to spur most of their star formation. But even minor mergers might not be major players. Writing in the July Astronomy & Astrophysics, Enrico Di Teodoro and Filippo Fraternali (both University of Bologna, Italy) studied 148 spiral galaxies and their environs. The results were surprising: 101 galaxies had no detectable companions, 15 had a massive companion, 6 had both massive and dwarf companions, and 26 had only dwarfs.

For the 32 spiral galaxies with dwarf companions, the team

found that any future mergers would only provide each spiral with at most 0.28 solar mass of gas per year — approximately a fifth of the gas necessary to continue forming stars.

One alternative is that minor mergers could trigger star formation via tidal forces by compressing the gas that’s already in the massive spiral. The impact on star formation from mixing up the spiral’s own gas might be larger than the impact from gas injected into the spiral from the dwarf. Also, dwarfs likely add a lot of their own stars to the spiral.

SHANNON HALL


GALAXIES | Surprising Black Hole in Dwarf GalaxyA supermassive black hole has been found in one of the most unlikely places — an ultracompact dwarf galaxy. The discovery strengthens the case for one of two models to account for the origin of such dwarf galaxies.

Ultracompact dwarf galaxies, first identified in 2000 by an international team involving several Australians led by Michael Drinkwater (now at the University of Queensland),

Holger Baumgardt (University of Queensland) and Richard McDermid and Lee Spitler (Australian Astronomical Observatory / Macquarie University) have used the Hubble Space Telescope and the 8.1-metre Gemini North Telescope on Mauna Kea to study the ultracompact dwarf galaxy M60-UCD1, the brightest known and most massive member of its class. Lying 54 million light-years from us, M60-UCD1 is about 22,000 light-years from the centre of the elliptical galaxy M60, itself the third largest galaxy in the Virgo Cluster of galaxies.

By analysing the motion of stars within M60-UCD1, the team was able to determine that the galaxy harboured a supermassive black hole with a mass of 20 million solar masses (about 15% of the entire galaxy!). That’s more massive than the black hole at the centre of our galaxy. Such a finding suggests that M60-UCD1 must have once been a much larger galaxy, and perhaps it had been cannibalised by its gargantuan neighbour M60.

GREG BRYANT

An artist’s impression of the gigantic black hole lying at the centre of the ultracompact dwarf galaxy M60-UCD1. NASA, ESA, AND D. COE

AND G. BACON (STSCI)

have puzzled astronomers trying to understand how these intrinsically dense structures (less than 200 light-years across and with masses of up to the equivalent of 200 million Suns) came to be. Two models are that they are either the tidally stripped remains of much larger galaxies or that they are massive types of globular clusters.

Now a team headed by Anil Seth (University of Utah) and including

The local universe appears to be missing a whole lot of ultraviolet photons. Juna Kollmeier (Carnegie Observatories) and colleagues report their discovery of this “photon underproduction crisis” in a study published in the July 10th Astrophysical Journal Letters.

The ultraviolet radiation permeating the universe has two main sources: quasars and young, hot stars. Their UV photons interact with the sparse gas pervading intergalactic space, converting neutral hydrogen atoms into electrically charged ions. Quasars probably account for most of the extragalactic UV background, because ultraviolet light from stars is usually absorbed by their host galaxies before it can reach the intergalactic hydrogen.

Observations of the distant cosmos (i.e.

stuff that existed about 12 billion years ago or earlier) show near-perfect agreement between the number of UV sources and the ionisation rate of intergalactic hydrogen. But Kollmeier’s team found that in the local universe, the amount of UV radiation produced by known sources was one-fifth the amount needed to account for observations of local intergalactic gas.

The crisis shows a significant discrepancy between our current models and our observations of the present-day universe, but none of the possible explanations is totally satisfactory. Astronomers might need to completely reevaluate how much UV radiation comes from quasars and young stars, as well as how much stellar radiation escapes the stars’ host galaxies.

A more exciting alternative is that

hitherto undiscovered sources dominate the local universe’s UV background, such as decaying dark matter. “You know it’s a crisis when you start seriously talking about decaying dark matter!” says study coauthor Neal Katz (University of Massachusetts, Amherst).

MARIA TEMMING

INTERSTELLAR SPACE I The Mystery of the Missing Light

A simulation of intergalactic hydrogen in a “dimly lit” universe compared with one of a “brightly lit” universe. Observations match the right-hand picture, but simulations using only the known cosmic ultraviolet sources produce the much thicker structures on the left. B. OPPENHEIMER / J. KOLLMEIER


News Notes

A Quasar Main Sequence? A new diagram is the closest astronomers have come to uniting quasars’ diverse optical properties with what’s actually going on physically. Building off decades of previous work by others, Yue Shen (Carnegie Observatories and Peking University, China) and Luis Ho (Peking University) looked at 20,000 quasars from the Sloan Digital Sky Survey and divided the sample based on two observed characteristics: the width of the hydrogen beta (Hβ) emission line and the strength of emission from singly ionised iron (Fe II). The resulting plot draws a “main-sequence wedge,” reminiscent of the Hertzsprung-Russell diagram for stars (AS&T: October 2014, p. 38). If, as the team concludes in the September 11th Nature, a wider Hβ line corresponds to a more edge-on disk and Fe II’s strength is a proxy for the black hole’s accretion rate, then the orderly diagram reveals a quasar’s orientation and accretion rate, simply based on where the quasar lies in the plot. Paired with luminosity, the accretion rate also reveals the black hole mass. The correlations will require much more testing before they’re confirmed. CAMILLE M. CARLISLE GRBs: A New Standard Candle? Two teams independently suggest that gamma-ray burst supernovae just might be “standardisable.” At first glance, the supernovae that create long GRBs have irregular light curves. But when Zach Cano (University of Iceland) and a second, independent team comprising Xue Li and Jens Hjorth (both from University of Copenhagen, Denmark) analysed separate sets of eight GRB supernovae, Cano found that the luminosity correlated with the light curve’s width, while Li and Hjorth found that the luminosity correlated with the light curve’s decline rate. The arguments are preliminary; the next step will be to successfully use GRBs as standard candles to confirm distances calculated with other tools. SHANNON HALL

IN BRIEFCOSMIC STRUCTURE I Laniakea: Our Home Supercluster

Astronomers have mapped the cosmic watershed in which our Milky Way Galaxy is a droplet. This massive structure extends more than 500 million light-years and contains 100,000 large galaxies.

The work, published in the September 4th Nature, is the first to trace our local supercluster on such a large scale. It also provides a physical way to define what a supercluster is, by delineating it based on the motions of its member galaxies.

Researchers have been working out the gravitational structure in our local universe for decades. Based on work by Gérard de Vaucouleurs in the 1950s, astronomers have thought of our galaxy as being on the edge of the so-called Local Supercluster, a structure about 100 million light-years wide that’s centred on the Virgo Cluster.

But astronomers have seen much larger structures in the universe, on the scale of several hundred million light-years. These maps have generally depended on calculating galaxies’ 3-D locations based on their cosmological redshifts.

Brent Tully (University of Hawaii, Manoa) and colleagues have taken a different approach. They used galaxies’ peculiar velocities, which are the galaxies’ motions due to the local gravitational landscape. Galaxies fall toward or away from one another in this landscape; the Milky Way and many others seem to be moving toward the Great Attractor, a dense region in the vicinity of the Centaurus, Norma, and Hydra clusters about 160 million light-years away.

Peculiar velocities are on the order of a few hundred kilometres per second, whereas cosmic expansion velocities rise to several thousand km/s in the nearby universe, reaching 10,000

A slice of the Laniakea Supercluster. The Milky Way is at the little blue dot toward the right-hand edge of the circled region (just below the reddish area, which is the Virgo Cluster). SDVISION INTERACTIVE VISUALISATION SOFTWARE BY DP AT

CEA/SACLAY FRANCE

km/s roughly 130 million light-years out. (A galaxy recedes faster the farther away it is.) There’s about 10–20% uncertainty in the peculiar velocity measurement for an individual galaxy. Only for nearby galaxies is the peculiar velocity high enough compared with the expansion velocity for astronomers to peg it confidently.

The team found a way around this problem by using a technique called Wiener filtering. This algorithm allowed the team to essentially take a step back and look at the big picture, revealing the large-scale flow patterns created by galaxies’ motions.

Last year, the team used this technique to map the local universe’s web of filaments, clusters, and voids. Now, they’ve taken a closer look using their Cosmicflows-2 catalogue, which contains more than 8,100 galaxies. The new catalogue reveals where the flows merge and diverge, unveiling a gargantuan structure on whose periphery the Milky Way sits. The Great Attractor is a central valley in this newly demarcated watershed.

The team calls this huge supercluster Laniakea, from the Hawaiian lani (heaven) and akea (spacious, immeasurable).

The analysis also reveals other structures, including a separate supercluster called Perseus-Pisces and a distant concentration named Shapley about 650 million light-years away, toward which Laniakea is moving.

Finding out if our supercluster is only the elephant’s trunk will require accurate distance measurements that reach three times farther than the current catalogue.

CAMILLE M. CARLISLE


IN BRIEFSOLAR SYSTEM | Powerful eruption wracks IoA titanic volcanic eruption seen on August 29, 2013, was among the most powerful ever recorded in the solar system. � e eruption followed two other, dimmer outbursts on August 15th and was captured simultaneously with the Gemini North telescope and the NASA Infrared Telescope Facility, both on Mauna Kea. � e outburst probably involved a cluster of towering lava fountains spread over an estimated 83 square kilometres. � e eruption’s location — within a few degrees of 223° west, 29° north — is not associated with any previously recognised volcanic site. Team member Katherine de Kleer (University of California, Berkeley) says that the event unleashed an estimated 20 terawatts of energy, making it at least 10,000 times more powerful than the lava fountains spewed during the 2010 eruptions of Eyja� allajökull in Iceland. � e team’s two analyses appear in the planetary science journal Icarus. Io is the most volcanic body in the solar system, with about 150 sites active now; the total site count is roughly 400. MARIA TEMMING

It’s A Planet!“Astronomers are almost ready to say it out loud: Beta Pictoris has a planet. Its orbit is 25 percent larger than Saturn’s, and its gravity has herded smaller objects into belts around the star the way our own Solar System’s planets have shaped the asteroid belt and the Kuiper Belt.

“Beta Pictoris achieved stellar astronomical status in 1983 when the Infrared Astronomical Satellite (IRAS) discovered a large, edge-on disc of gas and dust around the star. Imaging later revealed warps and tilts in the disc... Now, using

a high-resolution mid-infrared spectrometer on the 8.2-metre Subaru telescope, the Japanese team has analysed thermal emission... � e results strongly suggest that a giant planet orbits 12 au from the start.”

Some 63 light-years distant, Beta Pictoris’ planet was � nally con� rmed in 2008 when new processing of a 2003 image revealed its pinpoint presence. Studies since then have shown the planet orbits the star every 20 years at a distance of around 9 au. � e planet is about 7 times the mass of Jupiter and rotates every 8.1 hours.

Rosetta Flyby of Earth“On November 13th, Europe’s Rosetta comet probe made its last � yby of Earth before heading to the outer solar system.

“Launched in March 2004, Rosetta circled the Sun once before its � rst return in March 2005, which boosted its orbit out to meet Mars in February 2007. � e Mars � yby sent Rosetta into the inner asteroid belt 1.6 au from the Sun, then back to Earth in November 2007 for a further � ing out to 2.2 au and a � yby of the little asteroid 2867 Steins in 2008.

“� is � nal Earth � yby boosted Rosetta to Jupiter’s distance at 5.1 au, where it will rendezvous with Comet 67P/Churyumov-Gerasimenko in 2014 and drop a lander onto its nucleus.”

Rosetta successfully arrived in orbit around the comet last August. As this issue was going to press, Rosetta’s comet lander Philae was preparing to land on Churyumov-Gerasimenko’s surface, the � rst time that a so� landing on a comet has occurred.

January 2005

January 2010

10 & 5 Years Ago

Astro CalendarVASTROCApril 17 - 19Discovery Science and Technology Centre, Bendigo, VicBiennial Victorian Astronomy Conference, hosted in 2015 by the Bendigo Astronomical Society.www.vastroc.net

South Paci� c Star PartyMay 14 – 17Ilford, NSWAnnual star party, hosted by the Astronomical Society of New South Wales.www.asnsw.com/spsp

CWAS AstrofestJuly 18 – 19Parkes, NSWAnnual conference incorporating the David Malin Awardswww.cwas.org.au/astrofest/

Queensland AstrofestAugust 7 – 16Lions Camp Duckadang, Linville, QldLong-running annual star partywww.qldastrofest.org.au

National Science WeekAugust 15 – 23NationwidePromoting and celebrating sciencewww.scienceweek.net.au

WHAT’S GOING ON? Do you have an event or activity coming up? Email us at [email protected].


FREE ASTRONOMY CALENDAR OFFER INSIDETHE TRUTH ABOUT 2012 p.32

10 Top Stories of 2009 p.28

An Australian student chooses this planetary nebula to be imaged with an 8-metre telescope. p. 44

Mars at Opposition: How to Observe and Photograph the Red Planet

Winning images from the David Malin Awards p.88

Test Report: Celestron’s Heavyweight CGE Pro mount p.80

Gemini’s Glowing Eye

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JANUARY 2005 A$7.50 INC GST NZ$8.20 INC GST

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Astronomy 2005 Year Book

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as&t january issue.indd 1 11/12/2004 8:18:17 AM

Jupiter's moon Io saw three massive volcanic eruptions within a two-week period in August last year. This August 29, 2013 outburst on Io was among the largest ever observed on the most volcanically active body in the solar system. NSF/

NASA/JPL-CALTECH//UC BERKELEY/GEMINI OBSERVATORY


Countdown to Pluto Greg Bryant

Less than a year before the New Horizon spacecraft flies past Pluto, astronomers using the

Hubble Space Telescope have successfully identified three candidate Kuiper Belt objects that the New Horizons spacecraft could be redirected to after this coming July.

When New Horizons was launched in 2006, it was planned that the spacecraft could be targeted to explore the Kuiper Belt after Pluto. At the time, there were no known Kuiper Belt objects beyond Pluto that could be reached by New Horizons, but scientists were confident that potential targets would be found.

Ground-based telescopes such as Keck, Magellan, Gemini, and Subaru were employed in 2011 – 13 to survey targeted regions. Those observing runs discovered more than 50 new Kuiper Belt objects, but none of them were reachable given the fuel constraints of New Horizons post-Pluto.

Running out of time, the New Horizons team applied for and received time to use the Hubble Space Telescope last winter. Hubble was able to image deeper than the ground-based telescopes could, and detected five new Kuiper Belt objects that would be relatively near New Horizon’s post-Pluto trajectory. Further observations ruled out two of them as plausible candidates, leaving three that would be reachable.

Of the three, one is easily targetable and has the temporary name “PT1” (Potentially Targetable KBO 1). If it is the one that is chosen as New Horizon’s destination, the spacecraft would fly past the object in January 2019. PT2 and PT3, the other two possible targets, will continue to be observed in order to refine their orbit. They appear to be larger than PT1 and thus perhaps more appealing.

In 2016, assuming that New Horizons has survived the Pluto flyby

Exploring Beyond PlutoNew targets have been found for New Horizons.

Below: This image combines multiple exposures taken with the Hubble Space Telescope to show the Kuiper Belt object PT1 moving against the background stars. PT1 can be seen moving from bottom left (just left of the bright star near centre) to top right. NASA, ESA, SWRI, JHU/APL, AND THE NEW HORIZONS KBO SEARCH TEAM

JupiterSaturn

Uranus

Neptune

Pluto

This artist’s impression shows a Kuiper Belt object some 6 billion kilometres from the Sun. Plotted for late 2018, three and a half years after New Horizon’s flyby of Pluto, the illustration also shows the positions of Jupiter, Saturn, Uranus, Neptune, and Pluto. NASA, ESA, AND G. BACON (STSCI)

and is safely on course to an encounter with another Kuiper Belt object, the team will formerly apply to NASA for an extension of the spacecraft’s mission. Meanwhile, New Horizons is scheduled to be woken up from hibernation in the first week of December (around the time this issue of Australian Sky & Telescope goes onsale). New Horizons will be “awake” from now until next July’s Pluto encounter, with science operations to begin shortly. The excitement is building. ✦


David EllyardDiscoveries

David Ellyard presented SkyWatch on ABC TV in the 1980s. His StarWatch StarWheel has sold over 100,000 copies.

January could be described as “expanding universe” month, since two major discoveries dealing with that

matter were announced in the month of January, though many years apart. One led us to the understanding that we live in a universe in which the major congregations of stars are moving apart; the other that the expansion appears to be accelerating.

We commonly credit the American astronomer Edwin Hubble with the first discovery. Certainly he and his colleague Milton Humason produced a paper in a leading journal in January 1929 with the necessary evidence. But he was cautious in interpreting his data, leaving that to others who he thought had more expertise. It was wise caution since the data was still sparse, though subsequent work by him and others confirmed it.

What had he found? Combining his own research with results from a number of other astronomers, he had built a data set of 46

galaxies. For each one he had an estimate of how far away it was and how fast it appeared to be moving away. The distance estimate came from locating within the galaxies examples of a special class of star called a “Cepheid variable” — a star which varied regularly in brightness in a time interval that was directly related to its absolute brightness. Such a star could serve as a “standard candle”. Comparing its apparent brightness with its known absolute brightness indicated how far away it was.

The estimate of the speed of flight came from measuring “redshift”, an apparent reddening of light from the galaxy (to be more precise, a shift in spectral lines toward the red end of the spectrum). This was thought of as an example of the “Doppler Effect”, equivalent to the drop in pitch in an ambulance or police siren as it passes by and speeds away. On this interpretation, the greater the redshift, the faster the galaxy was moving.

The Growing Universe

When Hubble plotted his data, he could see the points grouped roughly along a straight line, though with a lot of scatter. This suggested a direct relationship between distance and speed; the farther away a galaxy was, the faster it was moving. That was as far as the cautious Hubble went. He suspected that new observations might alter the picture and so it was “premature to discuss in detail the obvious consequences of the present results.”

But as time went by and the observations piled up, the “consequences” became plain. Our universe appears to be expanding, with most galaxies moving apart (galaxies close together can draw even closer through gravitational attraction). In time, the relationship, now supported far further into deep space than Hubble could see, came to underpin the hypothesis of the Big Bang, put forward to explain why everything is on the move outwards.

Hubble has the general credit for all this, but he was not in fact the first to propose such a view. A year or so earlier, the Belgian priest-physicist Georges Lemaître had published a similar idea, citing much the same sort of evidence that Hubble had used, and giving the notion a backing from Einstein’s General Theory of Relativity. But it was in an obscure journal and did not get the attention it deserved, as least not until Hubble had spoken.

The relationship between distance and speed of recession of galaxies became known as Hubble’s Constant (though Lemaître’s Constant might be a fairer title since he estimated it first). It has been steadily revised downward over the time since, and now is only one tenth of Hubble’s initial number (he had greatly underestimated the distances to the galaxies). That has had the effect of making the universe both much bigger and much older than Hubble conceived.

Nor is it really a constant. Much more recent work, first announced in January 1998, indicates that the rate of expansion has increased during the latter part of the lifetime of the cosmos. This Nobel Prize-winning work, which included major contributions by Australian researchers led by Brian Schmidt (Australian National University), was based on measurements among the most distant and most ancient galaxies, and used supernovae as the “standard candles”. Why this has happened remains unexplained, though there is much talk about “dark energy”. ✦

A century ago, Cepheid variables were key in the quest to measure the Universe’s expansion. Now, the study of type Ia supernovae, which can be seen across even farther distances, is used to explore the changing expansion rate at different epochs in the Universe’s history. This image, taken with the Hubble Space Telescope, shows the type Ia supernova 1994D (bottom left “star”) in the galaxy NGC 4526. NASA/ESA, THE HUBBLE KEY PROJECT TEAM AND THE HIGH-Z SUPERNOVA SEARCH TEAM

“Perfection” — Wolfgang Promper

Wolfgang Promper recently took an FLI MicroLine MLx694 to Tivoli AstroFarm in Namibia. Paired with the Tele Vue NP127, CenterLine filter wheel, and Atlas focuser, the results were spectacular! His review:

“The sensitivity is amazing, the noise extremely low, but what I really felt is that it is the perfection we all are looking for. Every subframe looks like a calibrated master and it connects you directly to the object you’re imaging. If it were a musical instrument, I would compare it with a Stradivarius.”

At Finger Lakes Instrumentation, we design and build unrivaled cameras, filter wheels, and focusers to pave your way to success—whichever path you choose. Designed and manufactured in New York, USA.

Visit us at www.flicamera.com

for more information about our cooled CCD

cameras, focusers, and color filter wheels.

Trifid Nebula imaged with MicroLine MLx694 and Tele Vue NP127. Image courtesy of Wolfgang Promper.

MicroLine MLx694 cameraReadout Noise: 3 electronsPeak Quantum Efficiency: 75%Cooling: 60°C below ambientDark Current: <1 electron/hour

© 2014 Finger Lakes Instrumentation, Inc. All rights reserved.

Finger Lakes Instrumentation

TM

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MercuryMeet the planet nearest our Sun

The innermost planet has challenged astronomers for centuries. Its proximity to the Sun limits ground-based

telescopic observations, and when NASA’s Mariner 10 spacecra� made three close passes during the 1970s, the little planet appeared to have a landscape that strongly resembled the Moon’s.

But Mercury is no Moon. NASA’s Messenger spacecra� , in orbit around the Iron Planet since March 2011, has recently � nished its initial global survey. � e work reveals that this wacky world has a unique, complex history all its own.

� e survey images show a marvellous world of ancient volcanic � oods and mysteriously dark terrain (AS&T: November/December 2012, page 32). Plains — mostly volcanic — cover about 30% of the surface. And as radar images have long suggested, subsurface water ice lies tucked inside some polar craters. Temperatures in the coldest craters never top 50° above absolute zero, making Mercury both one of the hottest and coldest bodies in the solar system.

To celebrate Messenger’s completed Mercury survey, we’ve worked with the United States Geological Survey to produce a labelled map of the innermost planet, which you’ll � nd on pages 20-21. � e labels on this map are a subset of those that now adorn Mercury. Many names honour artists, writers, and musicians, including Bach and Copland. Even Disney and Seuss have craters.

Prokofi ev Crater’s north-facing rim and interior remain in perpetual shadow, making it a safe haven for water ice. Watch an animation of how illumination changes over the course of one Mercury day at skypub.com/prokofi ev. NASA GSFC / MIT / JHU APL / CIW



Mercury

Perihelion precesses2° per century

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Day 1762 orbits3 rotations

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Mercury’s Strange Orbital Dance

Mercury rotates three times for every two orbits around the Sun. This 3:2 spin-orbit resonance means that for a hypothetical astronaut on the surface (black dot), sunrise comes only once every 176 Earth days. At perihelion, dayside temperatures reach about 700 K; at aphelion, 500 K.

S&T ILLUSTRATIONS: GREGG DINDERMAN

GLOBE MAP: USGS / NASA /

JHU APL / CIW

The perihelion of Mercury’s orbit precesses 2° per century. Astronomers could explain all but 43″ of that shift with classical mechanics; they needed Einstein’s theory of gravity to explain the rest. The orbit’s elongation and advance are highly exaggerated to emphasise the e� ect.

This Messenger image shows mysterious “low-refl ectance material” excavated by craters near the eastern edge of Caloris Basin. The reddish deposits appear to be volcanic in origin. The orbiter took this composite image using all 11 colour fi lters of its wide-angle camera.

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Due to Mercury’s unique 3:2 spin-orbit resonance, NASA’s Messenger spacecraft took nearly two years to record the entire globe in daylight conditions. Mission scientists combined thousands of images to create a monochrome base map with a resolution of roughly 170 metres per pixel. Then they merged it with a second, less detailed mosaic — consisting of images taken through blue (430 nm), red (750 nm), and near-infrared (1000 nm) fi lters — to bring out subtle colour di� erences. Note: regions poleward of 75° latitude appear only in the polar maps.

South Polar Region

© 2014 SKY & TELESCOPE


Mysteries of Planetary Nebulae

ROBERT ZIMMERMAN

Gull’s � rst images ba� ed him. In red wavelengths the star looked like a rectangle. “What in the world is going on with this system?” said Gull. To make sure the shape wasn’t an artefact he took another image of a nearby star. It was a sharp point. HD 44179, however, remained “a crisp, rectangular object.”

And thus the Red Rectangle was found.

Observations in the ensuing decades have not only produced even more amazing images of this strange angular object, they have added further mysteries. In 2003 a Hubble Space

In October 1973, the 4-metre Mayall Telescope at Kitt Peak in Arizona was just starting operations. Ted

Gull (now at NASA/Goddard Space Flight Centre) was using the telescope to produce some spectacular test images.

Seeing the images, Martin Cohen (University of California, Berkeley) was impressed and asked Gull to use the telescope to photograph a particular star Cohen had spotted earlier that year using a U.S. Air Force sounding rocket. � is star, HD 44179, was intriguing because of its unusual brightness in the infrared.

Telescope image revealed some inexplicable features, including four spokes on which were hung a series of “ladder rungs,” or nested rectangles of increasing size. � e structure almost looks as if a giant spider was weaving a web in space, stringing its thread from one beam of light to another.

What is really most astonishing about the Red Rectangle is that it is actually typical for a planetary nebula. In the past 20 years Hubble has given us our � rst high-resolution look at a large number of these weird and enigmatic objects and found that, more o� en than not, they are as complex, as astonishing,

Spider Websin Space

Astronomers are still puzzled by how stars create the bizarre variety of planetary nebulae in our galaxy.

STELLAR WEB The nebula surrounding HD 44719, known as the Red Rectangle, has ba� ed astronomers since its discovery in the 1970s. Explanations range from a bipolar fl ow seen at an odd angle to light leaking out through gaps in a dusty doughnut of material. NASA / ESA / HANS VAN WINCKEL (CATHOLIC

UNIVERSITY OF LEUVEN) / MARTIN COHEN (UNIVERSITY OF

CALIFORNIA, BERKELEY)


and as baffling as the Red Rectangle.From this new data astronomers are

beginning to put together a coherent outline of the origins and shapes of planetary nebulae. That picture is also giving astronomers a deeper understanding of the evolution of Sun-like stars. “By figuring out how these shapes transform we can learn to understand how stars really die,” explains Raghvendra Sahai (NASA/JPL).

Even more exciting, scientists are beginning to suspect that the presence of exoplanets might explain the strange shapes of some planetary nebulae. “I like to say that we are putting the ‘planet’ back into ‘planetary nebulae,’” adds Sahai.

The First DiscoveriesAlthough the first planetary nebula, the Dumbbell Nebula (M27), was discovered by Charles Messier in 1764, it was William Herschel who gave these objects their name when he conducted his survey of the Northern sky in the late 1700s. They reminded him of Uranus, the planet he had just discovered — even though he knew that what he saw was absolutely not a planet. All told, Herschel found 33 planetary nebulae, though of these he mislabelled 13 as something else. (He also dubbed another 59 objects as planetary nebulae that turned out not to be.)

Since then, and especially since the repair of Hubble in 1993, scientists have found planetary nebulae in a bewildering variety of shapes. About a quarter or more have bipolar lobes extending out from their centres. About 20% have multiple lobes. Others appear oval, some look like barrels, and some resemble cylinders that have been squeezed in the centre. A few even have spiral arms almost like galaxies. In a number of cases the central star is often offset from the centre of the nebula, even when that nebula is highly symmetrical.

And then, like the Red Rectangle, there are some whose complex patterns and shapes are too difficult to describe in a mere sentence. You have to look at a high-resolution image of each to understand it.

Astronomers have so far identified approximately 3,500 planetary nebulae in the Milky Way. Based on a count of the planetary nebulae within 2 kiloparsecs (6,500 light-years) of the Sun, they extrapolate that the Milky Way’s population includes anywhere from 11,000 to 28,000.

Stellar EvolutionPlanetary nebulae form during a very short phase late in the life of Sun-like, low-mass stars. During this stage the star is known as an asymptotic giant branch (AGB) star, the name referring to the location of these stars on the Hertzsprung-Russell Diagram (AS&T: October 2014, p. 38).

AGB stars are somewhat unstable. In this stage the star’s core is mostly oxygen and carbon, surrounded by an inner shell of helium with an outer shell of hydrogen. Most of the fusion goes on in the outer hydrogen shell, which produces helium that rains down onto the helium shell below, increasing its density. Eventually this increased density ignites the helium in an explosive pulse called a helium flash, pushing against the hydrogen shell so that it expands, becomes less dense, and stops burning.

The helium shell burns for a while, then shuts down. The hydrogen shell then settles, becomes dense enough to again ignite, and kicks off the whole cycle again.

This helium-flash process repeats many times, and during this phase the star begins to send out a wind of high-density dust made of carbon and other

heavy elements dredged up from the dying star’s core. This dust drags gas from the star’s fluffy outer envelope with it. The winds spew out anywhere from half to 90% of the star’s mass and form a dense envelope surrounding the star.

As these low-mass stars burn off the last bits of their hydrogen and helium fuel while losing mass, their cores begin to evolve into a white dwarf, made up of the carbon and oxygen core that’s not dense enough to burn. The wind changes from a slow high-density wind into a fast low-density wind that collides with the older circumstellar cloud. At the same time the star’s surface temperature increases to as high as 30,000 kelvin, and the intense radiation ionises the surrounding gas clouds, causing them to glow.

Thus begins the planetary nebula phase of the star’s life. The complex interaction between these two clouds, plus ultraviolet radiation from the star’s hot surface, combine to shape the planetary nebula and make it visible.

The transition from an AGB star to a planetary nebula happens very quickly, no more than a few centuries and sometimes as short as a few decades. The planetary nebula phase that follows

NGC 5189

NASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA)



three of the possibilities.)For example, one theory posits that

because the density of the older outer envelope might be different in different places, the later high-speed winds will tend to flow faster and farther into the more tenuous regions. In most cases, this means the inner wind will flow out the poles, producing a bipolar shape. In other cases, the inner wind punches through at different spots to produce a multi-polar planetary nebula.

This theory is inadequate, however. For example, one feature seen in about half of all planetary nebulae is point symmetry, where each point on one side of the nebula matches a corresponding point on the other side. Point symmetry can produce some incredibly complex shapes, such as the

will then last a few tens of thousands of years. Lacking nuclear fuel, the star’s winds eventually die off, the nebula steadily dissipates away, and we are left with nothing but a small and very compact white dwarf star that will slowly cool and fade away.

Shaping the NebulaVery few planetary nebulae are round. Even those few that appear round might only look that way because we happen to be viewing them at a particular angle. Somehow, the shaping process turns the spherical AGB cloud into something much more complex. But astronomers lack a good theory to explain this change. Instead, they have many theories, none of which seems to fit all the observations. (See page 30 for

Spirograph Nebula and the Cat’s Eye Nebula. Both are point symmetric, but unlike bipolar objects, they look very different from each other.

An inner fast wind impacting an outer older envelope can’t produce such complex point-symmetric shapes. If the AGB star was part of a binary system, however, the interaction between the two stars could do it. As the stars orbit each other they can churn the winds in many different ways to create point symmetry.

For example, what if the secondary star is close enough to the primary to accrete matter from it? The material would gather in an accretion disk around the secondary, spurring a fast bipolar wind that would blow out along the secondary’s poles into the older

Boomerang Nebula PGC 3074547

NASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA) AND ESA / HUBBLE COLLABORATION


Ring Nebula M57

HUBBLE SPACE TELESCOPE / LARGE BINOCULAR TELESCOPE / SUBARU TELESCOPE / ROBERT GENDLER



circumstellar envelope surrounding both stars. This could further churn up the nebula and produce a wide variety of 3-dimensional patterns that the primary couldn’t create on its own.

The problem is that, according to recent data, only about half of all planetary nebulae come from binaries in tight enough orbits to do the job. For the remainder, something else must produce the nebula’s complicated shape.

Some scientists have proposed that the star’s magnetic field might help sculpt the nebula. The problem here is that the amount of magnetic energy used to fashion the cloud would suck the angular momentum from the star in only a few decades. Something else must replenish that energy.

Most recently, some astronomers have begun considering the possibility that exoplanets might help solve this energy-loss problem. The angular momentum the star gains from swallowing a Jupiter-size exoplanet could be sufficient to replenish the energy of its magnetic field. As Wouter Vlemmings (Chalmers University of Technology, Sweden) said recently at a planetary nebula conference,

“In principle a planet could handle it.”

It’s also quite possible that — instead of one single overarching theory of formation — each planetary nebula is formed in its own unique way. Some develop as they do because the stars are binaries, others because the star has a strong magnetic field and exoplanets. Many others might assume their complex forms because the outer cloud has its own unique shape, which helps guide the later fast winds coming from the evolving star. And finally, some planetary nebulae might form because of a combination of all of these factors.

The Red RectangleThe Red Rectangle is an excellent example of why astronomers remain challenged by planetary nebulae. Computer simulations have suggested that the object’s strange rectangular shape is merely a result of our viewing angle: we are looking directly at the side of a bipolar nebula made up of two cone-shaped lobes. From this angle the edges of the cones stand out so that instead of cones we see four spikes. The ladder rungs stretched between the two spikes on either side are merely

Eskimo Nebula NGC 2392

Frosty Leo Nebula IRAS 09371+1212

Spirograph Nebula IC 418

Blinking Planetary NGC 6826

Ant Nebula Menzel 3

NASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA)

B. BALICK AND J. ALEXANDER (UNIV. OF WASH.) / A.

HAJIAN (U.S. NAVAL OBS.) / Y. TERZIAN (CORNELL) /

M. PERINOTTO (UNIV. OF FLORENCE) / P. PATRIARCHI

(ARCETRI OBS.) / NASANASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA)

NASA / ESA / ANDREW FRUCHTER (STSCI) / ERO TEAM (STSCI / ST-ECF)

ESA / HUBBLE / NASA



evidence of repeated eruptions that over time burst out of the star and formed the two bipolar cones. From the side, these waves of debris appear as straight lines.

The Red Rectangle itself surrounds a binary system where the secondary star is ripping matter from the primary as it orbits it once every 318 days or so. It is from this secondary, thought to be a main-sequence star slightly less massive than our Sun, that the bipolar jets that form the Red Rectangle’s X-shaped nebula are thought to come. The material pulled from the primary forms a thick rotating accretion disk around the secondary, which acts to direct as well as feed the cone-shaped bipolar jets flying outward above and below.

Sounds good, doesn’t it? The problem is that this scenario leaves many questions unanswered. For example, why are the two bipolar lobes cone-shaped rather than wineglass-shaped, as with most bipolar planetary nebulae? Scientists aren’t sure. One theory proposes that the X-shaped cones are really nothing more than light beams leaking through gaps in the inner torus, not two bipolar lobes seen from the side. Another theory says that the lobes are far older than estimated, and that what we’re really seeing are not the full lobes, but the stems of the much larger wine glasses, most of which have now dissipated.

Then there is the speed of the Red Rectangle’s expansion. Unlike most planetary nebulae, which expand quickly to form in only a few hundred years, the Red Rectangle’s expansion rate is very slow, suggesting the object’s formation took much longer, on the order of 14,000 years. Of this type of planetary nebulae, “We’re not sure what’s going to happen to them,” explains Sahai. “We understand them poorly.”

Then there are some of the Red Rectangle’s smaller features. The ladder rungs suggest that they were produced by a series of eruptions spaced by a few centuries that are now expanding like smoke rings along the lobes. Unfortunately, as Nico Koning (University of Calgary, Canada) explains, “We know of no known process that produces these shells in the time sequence seen.”

These questions are typical for all planetary nebulae. Although astronomers have developed good theories to explain their shape and origin, no theory as yet really manages to explain everything. “We have conferences every five years or so and seem to rehash the same questions each time,” notes Koning. “Progress in this field seems very slow.”

Which makes one wonder: maybe there are giant spiders weaving webs amidst the stars.

Robert Zimmerman is a contributing editor of S&T. His webpage is http://behindtheblack.com. His classic history of the 1960s space race, Genesis: The Story of Apollo 8, is now available as an e-book.

Dumbbell Nebula M27

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SHOWN HERE are three scenarios that might create planetary nebulae’s strange shapes, with real examples that might (or might not) be the products of these scenarios.

In one version of the slow-then-fast wind (A), the spinning star puts out a dusty shell of gas that’s denser around its equator. When the star later expels a fast wind, the wind rams into and is funneled by the older material, creating a bipolar outfl ow.

In a binary system (B), one of the two stars expels its shell as the stars orbit each other. The shell is squeezed in the direction the star travels, creating denser material in front of the leading side. As the stars orbit, the shell’s expansion pushes the pattern of compression outward, creating a spiral pattern.

A third idea is that the star’s magnetic fi eld might play a role (C). After the star has thrown o� its dusty gas layer, the

exposed carbon-oxygen core is highly magnetised. One of several theories posits that, as the core spins, it twists up its magnetic fi eld. Twisting the magnetic fi eld makes the fi eld want to expand. Because of the way the magnetic fi eld reacts to the twisting, the expansion will be faster along the star’s poles and along the equator, creating something that looks like a dumbbell wearing a tutu. This expansion shoves the surrounding gas envelope outward.

Three Ideas for Creating Planetary Nebulae

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Exoplanet Atmospheres

JONATHAN FORTNEY

Weird WeatherAstronomers have gone beyond merely counting

exoplanets to studying their atmospheres.

interior, atmospheric study can do more than just describe current average conditions. Exoplanet atmospheres are the key to understanding planet formation and evolution, including the physical and chemical processes at work in the past as well as in the current day.

Characterising AtmospheresThe easiest atmospheres to study are those of transiting hot Jupiters, gas giants that swing across the faces of their parent stars once every few hours or days. Astronomers can capture light emitted from, transmitted through, and reflected off their atmospheres. Astronomers can also image infrared light emitted from young, still-warm planets orbiting very far from their host stars.

A well-studied example of the former is HD 189733b, a hot Jupiter 63 light-years away. Slightly larger than Jupiter, this planet passes in front of its parent star every 2.2 days as seen from Earth, blocking about 2.4% of the star’s light. HD 189733b has been observed with every technique in the transiting-planet toolkit.

The first method, which works only for those planets that happen to transit their parent star, is transmission spectroscopy: during the transit, astronomers collect the spectrum of starlight that passes through the planet’s

Our solar system is a marvel filled with magnificent specimens of planets. Yet for

all its beauty, we now know that it is a poor showcase for the remarkable diversity of known planetary systems. Nature does not have any particular interest in our system’s regular ordering of rocky planets on inner orbits and gas giants on outer orbits. The final outcomes of haphazard planetary-system evolution can lead to planets ending up in strange places, far from where they formed and with properties where our Earthbound intuition fails.

A closer look at extrasolar worlds highlights their diversity. We observe water clouds on Earth and methane clouds on Titan, but we have no solar system equivalent of the clouds of rock dust and iron that we detect on the hottest planets. We live within Earth’s weather systems and observe storms on Jupiter and Saturn (AS&T: July 2014, page 38). But other planets face weather far more extreme, where winds gust faster than the speed of sound and shock waves ripple through the air. How can we understand these worlds when they lie so far outside our realm of experience?

Studying exoplanet atmospheres requires several cutting-edge techniques. And since a planet’s atmosphere either samples the nebular gas from which it formed, or arises out of gases liberated from the planet’s

on Alien Worlds

atmosphere. Water vapour, gaseous metals such as sodium and potassium, and the droplets or crystals that form in clouds can all selectively absorb the host star’s light, making the transiting planet’s diameter appear larger at some wavelengths. This tiny effect (HD 189733b’s atmosphere blocks only about 0.05% of its star’s light) is most commonly observed using the Hubble and Spitzer Space Telescopes and large ground-based telescopes.

HD 189733b’s transmission spectrum is well known in exoplanet circles for its lack of features — none of the expected molecules absorb the star’s light at visible or near-infrared wavelengths. Instead, clouds are most likely absorbing or scattering light across a wide wavelength range. And since the planet’s close orbit keeps it simmering at temperatures between 600°C and 900°C (between 900K and 1200K), these clouds are unlike anything we see on Earth. The conditions are just right for molecules that are typically gaseous in hotter worlds to condense into liquids and solids — in other words, it’s possible HD 189733b has clouds and rain of silicate and iron droplets.

Because Hubble’s near-infrared transmission spectra can detect water vapour in the steamy atmospheres of other hot Jupiters, such as HD 209458b, XO-1b, WASP-12b, WASP-17b, and WASP-19b, we know they must be less thick with clouds. But the water


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might enable us to pinpoint where these planets formed. Planets forming outside the snow line, where molecules such as water and carbon monoxide condense into solid ice grains, might incorporate less of these molecules into their gaseous envelopes than planets that form inside the snow line.

Observing occultations in infrared radiation also allow for the best constraints on a planet’s dayside temperature. Spitzer data show that HD 189733b’s dayside temperature hovers around a decidedly uncomfortable 900°C.

Astronomers can learn even more about a planet by measuring its orbital phase variations, the changes in thermal emission throughout its orbit. Most hot Jupiters orbit so closely that they become tidally locked, rotating so slowly that they always show the same face to their star. So if Spitzer observes an entire planetary orbit (over the course of a few days for a hot Jupiter), then it will capture thermal emission from both the permanently illuminated dayside and the permanently shadowed nightside.

Phase variations for HD 189733b show that the nightside is only about 200°C cooler than the 900°C dayside, a much smaller difference than expected. Day-to-night winds might redistribute heat between the two hemispheres, but

absorption features are far weaker than expected for clear atmospheres; layers of clouds or haze are probably common among hot Jupiters.

Another opportunity to characterise planetary atmospheres occurs when a planet passes behind (or is occulted by) its parent star in a secondary eclipse. Molecules and clouds in the planet’s atmosphere scatter starlight, and that light disappears when the star itself blocks our view. Hubble observations of one of HD 189733b’s occultations determined that the planet would appear an azure blue if we could see it up close. The colour likely comes from Rayleigh scattering, the scattering of light by small particles that is responsible for Earth’s blue sky. But whereas molecular nitrogen scatters sunlight, it’s not yet clear what molecules scatter the starlight in HD 189733b.

Hot Jupiters, like irons in the fire, emit thermal infrared radiation that also disappears when the star occults the planet. Spitzer has measured occultations of nearly 50 planets to date, detecting absorption features due to water vapour, which is seen in HD 189733b using this technique, as well as methane, carbon monoxide, and carbon dioxide in other planets. Determining the abundances of carbon- and oxygen-bearing molecules

Characterising AtmospheresOCCULTATION (SECONDARY ECLIPSE) A transiting planet’s thermal radiation and reflected light disappear when it passes behind its parent star. Astronomers can work backwards to determine the planet’s brightness.

TRANSIT (PRIMARY ECLIPSE) With a few hours of observing time, astronomers can collect a transmission spectrum of starlight passing through a transiting planet’s atmosphere.

ORBITAL PHASE VARIATIONS Between 30 and 100 hours of observing time enable astronomers to track the change in a planet’s brightness throughout its orbit.

TRANSMITTING STARLIGHT A transiting planet will appear slightly larger at certain wavelengths as molecules within its atmosphere selectively absorb starlight. Astronomers observe transits in multiple wavelengths to extract spectra and determine what molecules exist in the atmosphere.

to match observations, they would have to gust at speeds up to 12,000 kilometres per hour, faster than the local speed of sound. If slower (50 km/h) vertical winds help mix up gas layers, then the day-to-night winds might blow slightly less fiercely, at 6,000 km/h or so. Three-dimensional atmospheric models show that wind circulation patterns would feature only

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a few wide jets, rather than the � ne bands seen on Jupiter and Saturn, because tidal locking forces hot Jupiters to rotate more slowly, on the order of days rather than hours. Planetary-scale jet streams exceeding the speed of sound could leave parts of the atmosphere riddled with shock waves.

Another method for characterising atmospheric � ow is eclipse mapping, a more detailed way of analysing an occultation. During the beginning and end of a planet’s secondary eclipse, the star gradually obscures and reveals a planet’s dayside. Monitoring the planet’s light at � ne time resolution, astronomers can measure deviations from a uniformly bright dayside and map the planet’s brightness as a function of longitude and latitude. So far, this data-intensive method has only been applied to our favourite planet, HD 189733b, showing a “hot spot” blown slightly downwind from high noon, but work is underway to extend this technique to several others planets.

Beyond Hot JupitersHot Jupiters, with their large size and pu� y atmospheres, present the easiest targets for the current suite of observing techniques. But more recently astronomers have begun observing a smaller class of planets. � ese systems are scaled-down versions of hot Jupiters. Between Earth and Neptune in size, these planets circle small, cool stars in tidally locked orbits. No such mini-Neptune (or super-Earth) equivalent exists in our solar system, so we have little to guide atmospheric studies.

� e smallest of these planets observed so far is the mini-Neptune GJ 1214b, which contains the mass of six Earths (though it’s only 2.6 times Earth’s diameter), and transits a star only 42 light-years away. A wide range of ground- and space-based telescopes have observed the planet’s transmission spectrum, including a recent intense campaign by Hubble. Like HD 189733b, the observations show an atmosphere blanketed by thick clouds. � e transmission spectrum shows no absorption features in any wavelength range. Neptune-size planets such as GJ 436b show similar results. Clouds may complicate the characterisation of many small planets’ atmospheres.

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CLOUDS ON A MINI-NEPTUNE Hubble collected GJ 1214b’s transmission spectrum (right) over the course of 15 transits, showing data (white circles) that lack absorption features. With the long observation, astronomers were able to rule out “heavy” atmospheres of pure methane, water, or carbon dioxide (shown as green, blue, and red lines, respectively). Instead, it must be clouds that block any starlight attempting to penetrate the atmosphere in this wavelength range.

CLOUDY FORECAST It’s also possible that thick clouds in the atmosphere might block the host star’s light. In that case, even longer observing times will not enable astronomers to detect the atmosphere’s molecular imprint. S&T: LEAH TISCIONE; SOURCE: NAOJ (3)

HEAVY MOLECULES But an atmosphere made mostly of heavy molecules, such as water vapour or carbon dioxide, will hug the planet more closely. Most starlight will pass by unabsorbed, and the resulting transmission spectrum will appear featureless. Detecting molecules in such atmospheres is still possible, but requires much more observing time.

IDEAL TRANSMISSION SPECTRUM As the host star’s light passes through a planet’s atmosphere during the planet’s transit, molecules in the atmosphere reveal themselves by absorbing some wavelengths and not others.

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Perhaps the most intuitive method for characterising planetary atmospheres is to image a planet directly. Planets orbiting too close to their parent stars become lost in the glare of starlight, but direct imaging becomes feasible for planets on wider orbits. Large telescopes resolve planets far dimmer than their parent stars by using a coronagraph to block much of the starlight and adaptive optics to pick out the planet. So far, telescopes have directly imaged 18 planets (that is, objects less than roughly 10 Jupiter masses). � e benchmark system is HR 8799, where four gas giants orbit on long periods of 50, 100, 190, and 470 years, respectively. � is young system has only been around between 30 million and 90 million years, so the planets radiate at infrared wavelengths due to heat le� over from their formation. Infrared spectra and brightness measurements show that water vapour and carbon monoxide probably exist in these atmospheres.

A new instrument, the Gemini Planet Imager on the 8-metre Gemini South telescope in Chile, saw � rst light in November 2013. It can detect and measure spectra of planets that are up to 1 million times fainter than their host star. SPHERE, a similar instrument on the Very Large Telescope in Chile, is in the process of being commissioned. Both of these instruments will open the door to the atmospheric study of cooler, Jupiter-like giants.

The Structure of AtmospheresYou might expect deeper air to be warmer in a planet’s atmosphere, with the atmosphere cooling at higher altitudes. But on Earth, ozone in the stratosphere absorbs the Sun’s ultraviolet light, warming the upper atmosphere. All of the solar system’s gas giants also have temperature inversions; in these cases a layer of haze high in the atmospheres absorbs sunlight at visible wavelengths.

Using Spitzer’s occultation observations, astronomers have detected temperature inversions in some hot Jupiters — but far from all. If exotic molecules such as titanium oxide and vanadium oxide are stable on the hottest planets, as they are in the coolest stars, they would absorb starlight in the upper atmosphere. Planets that lack temperature inversion tend to orbit the most active stars, suggesting that intense ultraviolet radiation breaks up the absorbing compounds. But searches for direct detections of these compounds have so far been in vain.

Detecting whether life actually inhabits a planet depends on our ability to understand the planet's atmosphere...

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� e existence of a temperature inversion a� ects the deeper atmosphere. If molecules at high altitudes absorb incoming starlight, less starlight will penetrate to lower altitudes. For rocky worlds, the existence of these molecules helps set the surface temperature, along with greenhouse gases that absorb escaping infrared emission. On Earth, the ozone layer only slightly cools the surface, but on Titan, haze high in the atmosphere produces an “antigreenhouse” e� ect, absorbing sunlight that would otherwise warm the ground and heat the ground-level air. � is cools the surface by 9°C. By testing our ability to � nd antigreenhouse compounds on distant hot Jupiters, we hope to eventually do the same for smaller worlds.

The Atmospheres of Rocky WorldsA rocky planet’s atmosphere — especially its surface temperature and pressure — dictate whether it can support liquid water. Detecting whether life actually inhabits a planet depends on our ability to understand the planet’s atmosphere and predict the changes life would produce.

Many of the molecules detected in the atmospheres of gas-giant exoplanets, including water, methane, and carbon dioxide, would also be components of atmospheres hospitable to life as we know it. Take considerable care when thinking of molecules as “biomarkers,” features whose presence

ATMOSPHERE STRUCTURE Temperature generally increases deeper in the atmosphere, but absorbent molecules high in the atmosphere invert that trend, creating a warm layer up high (blue line). Without the absorbing layer, starlight can penetrate to heat the atmosphere from the ground up (red line). S&T: LEAH TISCIONE;

HOTSPOT By observing the changes in HD 189733b’s brightness as it orbits its parent star every 2.2 days, astronomers produced this global temperature map. Gusty winds apparently blow the hotspot 30° east of high noon. NASA / JPL-CALTECH / HEATHER KNUTSON (HARVARD-SMITHSONIAN CFA)

Sun-facing Longitude


HOT ROCKS: The rocky transiting planets Kepler-10b and CoRoT-7b orbit their parent stars so closely that their surfaces heat beyond 1300°C (1600K). Such planets appear to be Earth-like, made of rock and iron. But they are likely tidally locked, so models suggest their permanent daysides could feature lava oceans and a thin atmosphere of vaporised silicates, which could snow onto the very cold nightside.

STEAMERS: Planets made predominantly of rock and ice that form beyond their disk’s snow line, where it is cold enough for water to freeze solid, might later migrate closer to their star to become “ocean planets.” A deep layer of liquid water would cover such a planet’s surface and water vapour would dominate its atmosphere. 55 Cancri e, a super-Earth on an extremely short-period orbit, could be such a world.

SEASONAL ECCENTRICS: We experience seasons on Earth because its axis tilts relative to the orbital plane, not because of its slightly elongated orbit. However, exoplanets often have far from circular orbits; their average eccentricity, or elongation, is around 0.3, compared to Earth’s 0.0167. In the most extreme case, the gas giant orbits with an eccentricity of 0.97, similar to Comet Halley. In this case, the energy

hitting a planet will vary by a factor of more than 4,000 throughout the orbit. But even at an eccentricity of 0.3, it will still vary by a factor of 3½. We can expect many exoplanets to undergo extreme seasonal changes compared to the relatively steady climates of the solar system.

HOT JUPITERS: Roughly one out of 200 Sun-like stars hosts a giant planet zipping around on an orbit less than five days long. Silicate and iron cloud decks might make some of these planets highly reflective, but most are dark as coal. One hot Jupiter, TrES-2b, absorbs 99% of incoming light. Sodium and potassium vapour, and possibly titanium oxide, could permeate these planets’ atmospheres, absorbing nearly all visible light. (The planets still emit thermal radiation, though.) Moreover, wide planet-scale jet streams might reach several thousand kilometres per hour, sometimes surpassing the local speed of sound.

CIRCUMBINARY PLANETS: The first transiting circumbinary detected, Kepler-16b, orbits two stars every 229 days. Even though this planet’s orbit is nearly circular, its temperature likely changes as the stars orbit each other every 41 days. And if the stars eclipse from the planet’s point of view, brief dim periods would ensue.

Exotic Atmospheres COROT-7B

BROWN DWARFS: Astronomers have found more than 1,000 brown dwarfs, “failed stars” with masses too low to sustain fusion. They cool over time, some to temperatures as low as 30°C. Astronomers can test models of planetary dynamics and chemistry on these objects without the energy input or interfering glare of a parent star. Recently, scientists created this infrared brightness map of Luhman 16B, a brown dwarf 6.5 light-years away.NASA / JPL-CALTECH / TIM PYLE

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or abundance requires life. Oxygen and methane can be used as biomarkers on Earth, but only because we know how much of these gases come from a purely geological origin. To find evidence for the presence of life on an exoplanet, we would first have to show that atmospheric and geological chemistry cannot create the same signature. One day we may detect biogenic molecules

on extrasolar terrestrial worlds, but since determining their origin will require detailed study, we will need to be cautious in our interpretation.

The Near FutureSo far the study of exoplanet atmospheres has mostly been limited to gas giants. Tremendous excitement has centred on the characterisation of the mini-Neptune GJ 1214b, and the realisation that we can use our very same observational techniques on smaller planets. This has opened the door to even smaller planets, and the prospects for characterising the atmospheres of a wide range of small exoplanets are promising. To do that, we’ll need to find more (and closer)

Jonathan Fortney is an associate professor in the Department of Astronomy and Astrophysics at the University of California, Santa Cruz. His research focuses on understanding planetary atmospheres, interiors, and compositions.

transiting planets with additional observing power.

To that end, two space satellites are scheduled to launch in 2017: the European Space Agency’s CHEOPS (CHaracterising ExOPlanets Satellite) and NASA’s TESS (Transiting Exoplanet Survey Satellite). These small telescopes will find and measure small transiting planets around nearby bright stars. The following year NASA is scheduled to launch the James Webb Space Telescope (JWST), which will collect infrared spectra of these exoplanets. The observations will transform the field, as astronomers move from simply identifying molecules in atmospheres to determining their abundances.

To be sure, the atmospheres of true Earth analogues — Earth-size planets in Earth-like orbits around Sun-like stars — certainly lie beyond JWST’s reach. But we will likely characterise atmospheres of temperate super-Earths orbiting cool, small red dwarfs. Observations of their thermal emissions would show day-to-night temperature contrasts and atmospheric circulation.

Transit or occultation spectroscopy, which would detect molecules in these atmospheres, will require more stellar photons, which would in turn require significant commitments of telescope time from the astronomical community. Within a few years, we may be detecting water, methane, or carbon dioxide molecules in a small handful of the most promising super-Earths.

To find evidence for the presence of life, we would first have to show that atmospheric and geological chemistry cannot create the same signature.

DIRECT LIGHT In this image from the Keck II telescope in Hawaii, four young gas giants (b, c, d, and e) orbit the young star HR 8799, emitting their own near-infrared radiation due to heat left over from their relatively recent formation. RC-HIA / C. MAROIS / KECK

OBSERVATORY

FINDING MORE EXOPLANETS NASA’s Transiting Exoplanet Survey Satellite (TESS, left) and the European Space Agency’s CHaracterising ExOPlanets Satellite (CHEOPS, right) are both scheduled to launch in 2017, with the aim of finding and characterising exoplanets orbiting bright, nearby stars. CHEOPS: CHRISTOPHER

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Research Update

The 2014 Astronomical Society of Australia Awards

To explore the interaction between the AGN and its surroundings, Turner developed a model that brought the two Fanaro� -Riley classes back together. His new and improved hybrid model was built on a solid understanding of the physical processes involved and showed a certain � air for computational physics.

� e result has increased our understanding of how these galaxies work. � e AGN jet blasts a supersonic shock into the surrounding gas and Turner’s model describes how the gas � ghts back. If there is little interference and the jet is able to retain its high speed, then an FR-II galaxy is produced. Whereas, if the gas can force the jet to slow down to subsonic speeds, then an FR-I galaxy is formed.

Using this model, Turner was able to take observations of the size and luminosity of a galaxy’s lobes and compute the active lifetime of the AGN jet, the power it emitted, and the level of interaction between the AGN and its surroundings. � e AGN environment was shown to be capable of explaining the split that identi� es the two separate Fanaro� -Riley classes.

At the present time, Turner’s work has involved low-redshi� galaxies, ones that are relatively nearby so the jets and lobes can be studied in detail. In coming years, as Australia prepares for the ambitious Square Kilometre Array (SKA), data will � ood in for galaxies that are much more distant. � ese high-redshi� galaxies won’t be seen so clearly

Understanding Active Galaxies� is year’s Bok prize, awarded for best Honours or Masters thesis, was presented to Ross Turner from the University of Tasmania. His research on the evolution of radio-loud active galaxies was supervised by Stanislav Shabala (also from Tasmania).

Active galaxies emit more energy than can be generated by stars alone. It’s clear that something extra is going on, and the intense emission these galaxies produce o� en peaks within particular bands of the electromagnetic spectrum. Radio-loud active galaxies are those galaxies that shine strongly at radio wavelengths. � eir activity is powered by a supermassive black hole located right at the centre of the galaxy and generally referred to by astronomers as an active galactic nucleus (AGN). � e AGN produces a pair of strong jets, which burst out from the nucleus at speeds close to the speed of light. � ese jets smash into the surrounding gas and can in� ate massive structures known as lobes.

Some forty years ago, astronomers Bernie Fanaro� and Julia Riley identi� ed that radio galaxies fell into two separate classes: Fanaro� -Riley I (FR-I) galaxies are most luminous at their centre with the emission dwindling at larger distances, while Fanaro� -Riley II (FR-II) galaxies are brighter farther out, as a result of intense hotspots appearing along the edge of the lobes.

Each year the Astronomical Society

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From the Moon to Distant Galaxies

TANYA HILL


and therefore it will be models like Turner’s that will be important for interpreting this new data.

Lunar Neutrino DetectorJustin Bray, now a researcher at the University of Southampton, UK, was awarded the Charlene Heisler Prize for his doctoral research carried out at the University of Adelaide. He was jointly supervised by Ray Protheroe (University of Adelaide) and Ron Ekers (CSIRO Astronomy and Space Science). Bray’s work followed up on a novel idea that originated in the 1960s using the Moon as a neutrino detector, and produced substantial work covering the � elds of particle physics, radio instrumentation and

observations, and signal processing.Neutrinos are subatomic particles

produced in great numbers by astrophysical processes. But they do not readily interact with normal matter. � is makes them incredibly hard to detect and they are o� en referred to as ‘ghost-like’ particles. In fact, right this second, a billion neutrinos passed through every inch of your body as if you were made of empty space.

� e neutrinos that Bray was hoping to detect are those that are travelling incredibly fast or close to the speed of light, which are much rarer than their slower counterparts. When they hit the Moon, these high-energy neutrinos interact with the dusty layers of soil covering the lunar surface. A short

burst of radio emission is produced. It lasts for only a matter of nanoseconds but theoretically could be detected by radio telescopes.

� e rationale behind this research is to probe the origin of the highest energy particles in nature, called ultra-high-energy cosmic rays. Made up of fast moving protons and other heavier nuclei, when these particles strike photons (or particles of light) they produce high-energy neutrinos along with a range of other energetic particles.

By studying these neutrinos more can be learnt about their parent cosmic rays. � e Moon delivers the best chance of detecting high-energy neutrinos, because even though they are quite rare the Moon is big enough that it should be in the path of some of these neutrinos at some point. � is method also has the potential to detect cosmic rays directly.

Centaurus A, also known as NGC 5128, is a prominent example of a “radio-loud” active galaxy. Recent Australian research is helping to bring about a unifi ed model in our understanding of these active galaxies. ESO/WFI (OPTICAL);

MPIFR/ESO/APEX/A.WEISS ET AL. (SUBMILLIMETRE); NASA/CXC/CFA/R.KRAFT ET AL. (X-RAY)

The rationale behind this research is to probe the origin of the highest energy particles in nature, called ultra-high-energy cosmic rays.

Using the Parkes radio telescope, Bray conducted the most sensitive lunar radio experiment to date. And while no positive detections were made of either neutrinos or cosmic rays, valuable insights were gained into the techniques required for this type of experiment.

� e research was conducted as part of the Lunar Ultra-high-energy Neutrino Astrophysics with the Square Kilometre Array (LUNASKA) project. As with Turner’s radio-loud active galaxy work, this research will have implications for how the highly sensitive SKA could, quite possibly, deliver some of the � rst detections of high-energy neutrinos via lunar observations.


Research Update

A substantial result like that would open up the field of high-energy neutrino astronomy and create a new window on the universe. Because of the neutrino’s ability to travel across vast cosmic distances unimpeded, it could allow us to peer into the cores of distant galaxies and make discoveries that we haven’t even thought of yet.

Is Sodium Healthy?The Louise Webster Prize recognises excellence in research by an early-career astronomer. This year, the prize was awarded to Simon Campbell, now at Monash University’s Centre for Astrophysics, based on the significant scientific impact of the research paper “Sodium content as a predictor of the advanced evolution of globular cluster stars” published in Nature.

Campbell is primarily a theoretical astrophysicist, who builds computational models of stars to understand how stars evolve across their lifetimes. However, during his doctoral research he realised that stellar models weren’t keeping pace with observational findings. He followed this up by making his own observations of a globular cluster and in the process altered astronomers’ views on how stars can evolve.

Stars of similar or less mass than our Sun are generally expected to end their lives with a final burst of nuclear fusion. This last stage of old age is known to astronomers as the asymptotic giant branch (AGB) phase. It is when the richest production of chemical elements occurs deep within the star’s core. The AGB phase is also the period in a star’s life when considerable mass is puffed off by the star in the form of gas and dust. This gas and dust enriches the star’s local neighbourhood, releasing material that will go on to build the next generation of stars, planets, and even possibly alien life. The AGB phase is seen as incredibly important and is a standard feature in most models that simulate populations of stars within globular clusters.

However, as Campbell studied past research, he realised that some stars did not follow the rules. They appeared to completely skip the AGB phase and settled down more quickly and quietly into a white dwarf, the end product of low-mass stars.

The European Southern Observatory’s Very Large Telescope was

Stellar theory does not predict this behaviour as being so common and new models are now required to explain this startling observation.

Tanya Hill is the Curator of Astronomy at Melbourne Planetarium and is the Prizes and Awards Coordinator for the Astronomical Society of Australia.

used to separate out and study in detail individual stars within the globular cluster NGC 6752. Like other such clusters, this one consists of two generations of stars: an older or first generation made up of stars with a certain mix of heavy elements (such as sodium, oxygen, carbon and nitrogen) and a younger or second generation that is more enriched in certain elements, such as sodium and nitrogen. The second generation is usually more dominant and in NGC 6752 this is certainly the case, with second-generation stars accounting for 70% of the cluster population.

However, Campbell and his colleagues found that none of the second generation of stars appear to have made it to the AGB phase. All the observed AGB stars were first generation stars, confirmed by their low sodium abundances. This suggests that every second generation star is skipping the AGB phase and dying young. Stellar theory does not predict this behaviour as being so common and new stellar models are now required to explain this startling observation.

At the present time, the cause is unknown. It is clear that sodium abundance is a good indicator to track which stars will or won’t reach old age. But this is unlikely to be the root cause, although it must be strongly aligned with whatever process is at work.

The failed AGB stars are set to become very hot blue stars. Interestingly, this may help solve another problem in astronomy and explain why some elliptical galaxies shine brightly at ultraviolet wavelengths. It could be these failed AGB stars producing the excess UV light. Campbell and his team will be making further observations of a wide variety of globular clusters to help constrain their models of low-mass stars.

The Astronomical Society of Australia congratulates the 2014 ASA prize winners and was pleased to be able to showcase their work at the annual ASA scientific meeting. The author thanks the prize winners for their valuable assistance with preparing this article. ✦

The majority of stars in the globular cluster NGC 6752, imaged here with ESO’s Very Large Telescope, were found to not reach a long-theorised stage in their evolution, and their sodium abundance appears to be a key indicator. ESO

The Parkes radio telescope was pointed at the Moon (not for the first time in its history!) to search for radio emissions arising from the interaction of neutrinos with the lunar surface. SETH SHOSTAK

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AS�&�T Test Report Sean Walker

In recent years, specialised solar observing has spread through the amateur community like a

proverbial bush� re. Much of this was due to the growing availability of a� ordable narrowband � lters (primarily in the hydrogen-alpha line of 656.28 nanometres) using the Fabry-Perot etalon design. Suddenly, it became common to see solar prominences at star parties and other astronomical gatherings. Although many of these new � lters eliminated the need for powered temperature regulation, they were o� en mounted in front of a telescope objective. � is meant that to achieve higher resolution, you’d need a larger-aperture � lter, which in turn quickly becomes quite expensive for the larger models. DayStar, a company long associated with narrowband solar � lters, rolls out a slightly di� erent approach to the focuser-mounted etalon that promises to be much more versatile and a� ordable.

� e new DayStar Quark � lter “H-alpha eyepiece” (a more apt name would be an “H-alpha Barlow”) combines a telecentric Barlow with a small, power-regulated Fabry-Perot etalon used between your refractor’s eyepiece and diagonal. Besides a power source, the company claims that’s all you’ll need for views of the Sun at the H-alpha line in refractors up to 80 mm for “brief observing sessions” of the Sun. With the addition of a 2-inch UV/IR blocking � lter, the Quark is safe to use with telescopes up to about 120 mm (4 inches) before

The Quark from DayStar Filters

A new approach to a� ordable solar hydrogen-alpha fi lters.

a full-aperture energy-rejection � lter is recommended. As a longtime solar-telescope owner with aperture fever, I wanted to � nd out more, and requested the Chromosphere unit for further evaluation.

� e Quark � lters are about the size of a very large eyepiece, 14.6-cm long by about 5.7-cm wide. Each weighs in 400 grams, so expect to have to rebalance your scope when installing the unit. � e basic package comes with an AC adapter with various international plug attachments, end caps, and a large eyepiece bolt case. DayStar also included a 2-inch UV/IR blocking � lter that it recommends installing on a 2-inch diagonal when tracking the Sun while using the Quark on telescopes larger than 80-mm (3.1-inch) aperture for extended periods.

DayStar Instruments Quark FilterPrice: from $1,249Available from Astroshop

WHAT WE LIKE:

� Compact and versatile� Easy to use visually and photographically

WHAT WE DON’T LIKE:

� Requires fast refractor� Slow to adjust tuning

The Quark fi lter is as big as a large 2-inch eyepiece, and comes with end caps, a bolt case, and an AC adapter with international outlet adapters. All images are by the author.

� e � lter works by intercepting the light cone of your refractor before its focus point, allowing the use of a very small etalon while still taking advantage of your refractor’s full aperture. DayStar recommends using achromats or apochomatic refractors without additional correcting elements near the focuser. Optical designs with rear elements, such as the Petzval, and any oil-spaced objectives, require a full-aperture energy-rejection � lter for safe use. � e unit incorporates both 1¼- and 2-inch nosepieces, and is threaded to accept 1¼-inch accessories. Its 1¼-inch eyepiece holder incorporates a non-marring brass compression ring (which can be upgraded to 2-inch format).

Within the nosepiece is a 12.5-mm broadband blocking � lter that passes only a safe amount of light for viewing with small apertures. Immediately behind that is a 2-element telecentric Barlow-lens assembly that produces the 4.3× ampli� cation necessary for the etalon to function properly. At the eyepiece end is the � nal 21-mm back � lter.


The Quark in ActionI initially tried out the Quark � lter on a 4-inch f/9 achromat with a 20-mm eyepiece, using the supplied AC power adapter and the 2-inch UV/IR blocking � lter mounted in the front of my diagonal. Literature provided with the unit advises waiting about 5 minutes to enable the temperature regulation to stabilise; the small indicator light located above the tuning knob should change from orange to green when ready. When everything was all set, I looked cautiously through the eyepiece and focused. Although the view was adequate, I quickly determined the magni� cation a bit too much for our usual conditions here at the S&T o� ce, particularly because it was later in the day when local seeing conditions deteriorate. In this

con� guration, I found that using a 32-mm Plössl eyepiece was comfortable enough to take in the entire � eld, but still only showed a portion of the Sun. � is made it challenging to point the instrument to � nd prominences and active regions, particularly without an aiming device. Once I found an active region to focus on, the unit provided highly detailed views of � laments, light bridges within sunspots, and complex prominences.

As an avid solar observer, I prefer evaluating the entire solar disk, and then zooming in to active regions and prominences that warrant closer inspection. Because this wasn’t possible with the f/9 scope, I next tried out the unit on a 70-mm (2.8-inch) f/6.8 Tele Vue Pronto. � is proved to be an excellent match for the Quark; I was able to view the entire solar disk

The DayStar Quark Chromosphere fi lter provided a legitimate excuse for S&T sta� ers, including summer intern Maria Temming, to step outside the o� ce on many mornings. Using the fi lter with a 70-mm f/6.8 Tele Vue Pronto and Up-Swing mount produced excellent views across the entire solar disk.

Top: The Quark’s 1¼-inch nosepiece houses a 12.5-mm blocking fi lter that reduces the light entering the etalon to safe levels. Because the telescope’s light path is converging, this fi lter doesn’t constrict the light path at all. Above: the fi nal 21-mm fi lter before the eyepiece provides an evenly illuminated view of the solar chromosphere. The 1¼-inch eyepiece holder is upgradable to a 2-inch version.

with a 32-mm Plössl, and the reduced magni� cation when using a 40-mm Plössl was even more comfortable before I switched to higher powers.

In this setup, the solar disk displayed � laments and active regions across the � eld; there was very little band shi� as I approached the edge of the � eld, and this was only perceptible when I moved features to the very edge of the � eld. Prominences were easily visible along the limb.

� e Quark � lter uses a knob just above the power indicator to adjust the � lter tuning in 0.1-angstrom increments, spanning an entire angstrom. � is allows you to � nd the best tuning to see everything in the Sun’s chromosphere, or see blue- and red-shi� ed features. � is was probably the weakest feature of the Quark � lters — each turn of the knob required


AS�&�T Test Report

a wait of 5 minutes or longer to really see a change in the tuning of the � lter. In fact, it was di� cult to determine if there was any change at all unless I turned the knob 3 or 4 clicks. Users might have to spend some time � nding the best settings for their particular setup.

Overall, the views were quite nice through the Quark chromosphere � lter, though perhaps due to the long focal length of my scope/� lter combination, I felt the contrast wasn’t quite as strong as some other solar Hα � lters I’ve used in the past. DayStar doesn’t state the � lter’s exact bandpass range.

Left: Imaging through the DayStar Quark chromosphere fi lter was extremely easy and straightforward. Active regions around sunspots, fi laments, and prominences were all easy to capture using a Celestron Skyris 274M video camera. The author recorded this mosaic on the morning of July 5th, when the Sun was riddled with activity. Right: The extensive instruction booklet included with the Quark fi lter explains proper use of the fi lter as well as some excellent tips on imaging through the unit. It goes into detail on how you should tip your video or CCD camera slightly to eliminate the distracting interference pattern known as “Newton’s Rings” in the image above.

Photographic PerformanceImaging through the Quark was easy, and DayStar provides some excellent tips on how to do it in their well-written instruction booklet. I shot through the Quark Chromosphere � lter using a Celestron Skyris 274 video camera. Initially, I had interference bands across the image, but tipping the camera in the compression ring, as suggested in the booklet, eliminated the issue. Images through the setup, particularly with

the Tele Vue Pronto, were excellent. � e � lter produced no vignetting or passband shi� across the entire image, which enabled me to stitch together seamless mosaics of the entire Sun.

� e DayStar Quark Chromosphere � lter performed admirably, but with some conditions — the � lter functioned well in all the telescopes I used it with, and DayStar claims it will function safely with any size refractor with additional precautions. � e caveat is that unless you enjoy good to excellent seeing conditions regularly, you’ll need a relatively fast-focal-ratio refractor. So if you enjoy wide-� eld views of the Sun ringed with prominences, search for a really fast refractor with a focal ratio of about f/6 or better. � at still gives you a large range of options. Since safety is always a concern when using solar � lters, I consider the UV/IR-blocking � lter to be an essential purchase. � e modest power requirement is a small price to pay if you’re looking to step up to extreme-close-up views of the nearest star.

Imaging editor Sean Walker is always excited to see what’s going on in the solar atmosphere.

DayStar o� ers a 30-amp-hour battery pack with solar charger to power the Quark when observing where no AC power is available. The battery powered the Quark fi lter throughout the author’s late July weekend visit to the annual Stellafane Telescope Makers Convention in Springfi eld, Vermont.


New Product Showcase

New Product Showcase is a reader service featuring innovative equipment and software of interest to amateur astronomers. The descriptions are based largely on information supplied by the manufacturers or distributors. Australian Sky & Telescope assumes no responsibility for the accuracy of vendors’ statements. For further information, contact the manufacturer or distributor. Announcements should be sent to [email protected]. Not all announcements can be listed.

IMAGING COMPENDIUM Author and world-renowned astrophotographer Thierry Legault teaches you the art and techniques of astro-imaging in his book Astrophotography (US$39.95, or US$31.95 in eBook format). Legault’s compendium walks readers through the hows and whys of astronomical imaging, from basic camera-on-tripod skyscape photography to the more complex and demanding processes that use specialised telescopes and cameras for a variety of astronomical subjects, including the Sun, Moon, planets, artificial satellites, and deep-sky targets such as nebulae and galaxies. Legault shares his experiences to help you obtain the best results from a variety of equipment while guiding you through the common steps used to capture and process astronomical imagery. Paperback, 225 pages. ISBN 978-1-937538-43-9.

Rocky Nook802 E. Cota St., #3, Santa Barbara, CA 93103, U.S.Awww.rockynook.com

ECLIPSE COMPENDIUMS Astronomer and frequent Sky & Telescope contributor Fred Espenak releases two compendiums for eclipse chasers and researchers alike. Thousand Year Canon of Solar Eclipses: 1501 to 2500 (US$34.99, or US$51.99 in 4-colour print) is a comprehensive catalogue of essential characteristics of each of the 2,389 solar eclipses occurring throughout this 10-century period. The book presents fundamental concepts of eclipse classifications, as well as statistical analysis of occurrences, including the location of greatest eclipse duration. Global maps of the path of visibility are carefully plotted and arranged 12 per page. 294 pages. Thousand Year Canon of Lunar Eclipses: 1501 to 2500 (US$34.99, or US$51.99 in 4-colour print) does the same for each of the 2,424 lunar eclipses occurring in the 10-century time frame. 298 pages, 21½ by 28 cm, paperback.

AstroPixels PublishingP.O. Box 16197, Portal, AZ 85632, U.S.A.www.astropixels.com/pubs/index.html

COMPACT SPECTROGRAPH JTW Astronomy announces the Spectra-L200 (around $2,000), a slit spectrograph for amateur telescopes. Based on the Littrow spectrograph design, the Spectra-L200 allows users with modest telescopes to produce the high-resolution spectra needed to explore the structure and chemical makeup of stars and bright nebulae, or to see the redshift of distant quasars. A custom, multireflective entrance slit plate provides a unique arrangement of nine different slit gaps, ranging from 20 to 100 microns, and three pinholes that you can quickly select using a built-in thumbwheel. The unit attaches to your telescope using a female T-thread and weighs 1.2 kilograms. It performs best with telescopes having focal ratios of f/7 or greater. The heart of the instrument is a reflective grating positioned behind an oversized achromatic doublet. Its highly reflective chromium surface and transfer mirror enable you to directly track the target star through the guide port with your autoguiding camera. Additional gratings and accessories are available through the manufacturer’s website.

JTW AstronomyAalsmeerderweg 103M, 1432CJ, Aalsmeer Noord-Holland, The Netherlands www.jtwastronomy.com


OBSERVING JANUARY 2015

50 Binocular Highlight: Andromeda’s NGC 752

51 Southern Hemisphere Sky

52 Tonight’s Sky: The Celestial Twins

54 Sun, Moon & Planets: Jupiter Nears Opposition

56 Planetary Almanac

58 Celestial Calendar 58 An Aussie Comet Summer 59 R Reticuli

The Orion Nebula (Messier 42) is one of summer’s must-see sights. As you explore Orion, be sure to seek out the many double stars that lie within its boundaries (page 60). This image was taken with the MPG/ESO 2.2-metre telescope at La Silla Observatory, Chile. ESO/ IGOR CHEKALIN

60 Double Star Notes: Revisiting the Great Hunter

62 Exploring The Moon: Hunting for Lost Basins

64 Targets: Star Bound

68 Going Deep: Fuzzy Duos Inside the Circlet

IN THIS SECTION


Gary SeronikBinocular Highlight

Andromeda’s NGC 752Andromeda . . . blank. Go

ahead, fill it in. Andromeda Galaxy, right? Perhaps

no constellation is more strongly associated with a single deep-sky object than Andromeda. And for binocular observers, that’s doubly true — the Andromeda Galaxy (M31) is one of the finest targets in the sky (AS&T: October issue, page 74). But the constellation has more to offer. Although nowhere near as famous as its galactic neighbour, the open cluster NGC 752 is also a fine binocular sight.

The cluster is located about one binocular field south-southwest of 2nd-magnitude Almach, Gamma (γ) Andromedae. Alternatively, you could try my preferred route, which uses Gamma and Beta (β) Triangulum as pointer stars. Extend a line northward about 1½ times farther than the space between the stars to get to the cluster. No matter how you arrive, NGC 752 is an easy find under good skies.

In my 10×30 image-stabilised binoculars, NGC 752 has a spidery appearance with several curving rows of stars that converge toward the cluster’s centre. The two most prominent chains radiate eastward to form a sideways V, and a string of faint stars seems to define the cluster’s northern edge. Overall, it’s a fairly rich, large grouping with perhaps two dozen stars that pop into view. My 15×45s don’t add much to the scene, but make the individual cluster stars easier to see.

Although NGC 752’s discovery is often attributed to Caroline Herschel, it may in fact have been sighted first by 17th-century Italian astronomer Giovanni Battista Hodierna. Hodierna is perhaps best known for having made the earliest surviving drawing of the Orion Nebula. He made his deep-sky discoveries while surveying the sky for a never-completed star atlas. NGC 752 was likely one of his finds. ✦

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USING THE STAR CHARTWHENEarly December 1 a.m.Late December MidnightEarly January 11 p.m.Late January 10 p.m.

These are daylight saving times. Subtract one hour if daylight saving is not applicable.

HOWGo outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead.

FOR EXAMPLE: Turn the map around so the label “Facing NE” is right-side up. About halfway from there to the map’s centre is the bright star Procyon. Go out and look northeast halfway from horizontal to straight up. There’s Procyon!

NOTE: The map is plotted for 35° south latitude (for example, Sydney, Buenos Aires, Cape Town). If you’re far north of there, stars in the northern part of the sky will be higher and stars in the south lower. Far south of 35° the reverse is true.

ONLINEYou can get a sky chart customised for your location at any time atSkyandTelescope.com/skychart

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Greg BryantTonight's Sky

The Celestial TwinsGet to know a pair of stars and a pair of clusters.

The summer Milky Way, stretching from north to south, is climbing in the eastern sky on January

evenings. From a dark sky it’s a glorious sight — the arms of our spiral galaxy punctuated by the blazing brightness of nearby luminous suns. Many of the night sky’s key constellations have the Milky Way running through their boundaries. One that we’ll explore this month is Gemini — The Twins.

Gemini is rising in the northeast sky, becoming better placed for observing as summer rolls on. An easy way to find Gemini is to draw a line from Rigel to Betelgeuse, the two brightest stars of Orion, and extend it the same distance. That will place you right in the heartland of Gemini.

The constellation is best known for its two brightest stars, Pollux and Castor, the two “heavenly twins” which give Gemini its name (being Latin for “twins”).

Pollux is the southernmost (or highest in our sky) of the two and at magnitude 1.2 it’s the 17th brightest star in the night sky. An orange giant star, about two times the mass and nearly ten times the diameter of our Sun, Pollux is relatively close, at a distance of 34 light-years. In 2006, on the basis of measurements of the star’s radial velocity, it was announced that Pollux had a Jupiter-sized planet orbiting it every 1.6 years.

Castor is a little farther away (51 light-years) and a little fainter (magnitude 1.6) but it packs a surprise. Through a telescope at high magnification, Castor is

revealed to be a pair of bright stars (2nd and 3rd magnitude in brightness) with another 9th magnitude companion nearby. EACH of the three stars turns out to be a binary itself, though these extra stars are too close to their primary star to be seen. We’re not talking twins here — Castor is a sextuplet system!

Despite Gemini’s prominence, its proximity to the Milky Way band, and not to mention its size (514 square degrees, 30th in rank of the 88 constellations), it’s home to just one Messier object — the open cluster M35. Plotted on our all-sky chart on page 51, M35 shines at magnitude 5.1, making it visible to the naked-eye from a dark sky. The open cluster lies near the naked-eye stars 2.9-magnitude Mu (m) and 3.3-magnitude Eta (h)

Geminorum. If you have binoculars, all three will fit in the same field of view. Through binoculars, and in a low-power telescope, M35 is about the size of the Full Moon with a fairly uniform distribution of stars across its circular shape. Can you make out the smaller and fainter cluster NGC 2158? It lies southwest of M35 and despite their apparent proximity, it lies some five times farther away from us.

Perhaps you were gazing at Gemini in mid-December under a moonlit sky when the Geminid meteor shower was peaking (last month’s issue, page 62)? Take the time to find a clear night this month when the Moon isn’t interfering and become familiar with the celestial twins of Gemini. ✦

Visible to the naked-eye under good skies, the open cluster M35 is a fine sight in binoculars. Telescopes will also show the smaller open cluster NGC 2158, shown here at bottom right. N.A.SHARP/NOAO/AURA/NSF

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J1484 Wentworth Park Road Glebe NSW 2037. Tel: (02) 9518 7255519 Burke Road Camberwell Vic 3124. Tel: (03) 9822 0033

www.bintel.com.au

New www.bintel.com.auMon-Fri: 9am - 5.30pm Saturday: 9am - 4.00pm



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New

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Heavy load capacity


telescopes and/or

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Capacity 27kg.

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Sun, Moon and Planets Greg Bryant

Jupiter will be the headline planetary sight in January as it approaches next month’s

opposition, but there are also two pairs of evening planetary conjunctions worth catching.

Having been in conjunction with the Sun last month, Mercury returns to the western twilight sky this month, moving from Sagittarius into Capricornus early on. It’s a relatively poor apparition for Mercury, however, with the planet setting each evening before the end of twilight. Greatest elongation east of the Sun is on January 15, at 19o. Chief interest this month, however, is that Mercury will be closing in on Venus, with the pair just 0.7o apart on the evening of January 11. Venus at magnitude -3.9 will be some three magnitudes brighter than Mercury. If the bright sky hampers your attempts to � nd Mercury, seek out Venus using a pair of binoculars. Mercury will be in the binocular � eld of view for more than a week either side of their close approach.

A� er their close approach, both planets will separate as they continue to sink towards the western horizon. A 2-day-old Moon will join the scene on the evening of January 22, forming a triangle with the two planets, Mercury being the lower of the two. January 30 sees Mercury back in conjunction with the Sun.

Mars is low in the western evening sky, setting less than an hour a� er the end of twilight. Shining at 1st magnitude in Capricornus as the year opens before moving into neighbouring Aquarius, Mars is headed towards conjunction with the Sun in June and now only displays a disk about 4.5” in size as its distance from Earth continues to increase.

� is month sees a nice conjunction between Mars and 8th magnitude Neptune, though you’ll need at least a small telescope to see this. Closest approach between Mars and Neptune (0.2o) takes place during the daylight hours of January 20, so the evening of the 19th will see the pair 0.5o apart, and a little closer on the evening of the 20th at 0.4o. In the same � eld of view will be the 5th magnitude star Sigma (σ) Aquarii; Neptune and Sigma Aquarii will be at

Sky positions In Sun, Moon, and Planets, most descriptions that relate to your horizon or zenith — including directions like up, down, right, and left — are written for skywatchers in the world’s mid-southern latitudes. Confi gurations of the Moon with specifi c planets are a special case because they also depend on longitude, and these are given for Australia.

Jupiter Nears OppositionSpend summer nights observing the King of the Planets


their closest together (0.5o) on the 2nd. A 3-day-old Moon joins the evening scene with Mars on the 23rd.

Uranus is high in the northwestern evening sky as twilight ends, setting around midnight. Located in Pisces, near the Cetus border, Uranus is shining at magnitude 5.8. On the evening of January 25, Uranus will be about 1o from the Moon as seen from Australia. Some regions in the Northern Hemisphere will see an actual occultation. Australian observers will be able to catch some occultations of Uranus later in the year, so this month would be useful for seeing how comfortable you are in observing Uranus so close to the Moon.

Just weeks away from coming to opposition in February, Jupiter is rising very early in the evening. Shining at magnitude -2.5, Jupiter is in Leo and presents a disk around 45” in diameter by month’s end. � e king of the planets is unmistakable in the eastern evening sky, nearly four magnitudes brighter than nearby 1st magnitude Regulus,

ORBITS OF THE PLANETSThe curved arrows show each planet’s movement during January. The outer planets don’t change position enough in a month to notice at this scale.

Jan 2 Aldebaran 1.4o south of the Moon 5 Full Moon (3:53pm) 8 Jupiter 5o north of the Moon 9 Regulus 4o north of the Moon 12 Venus 0.7o southeast of Mercury 13 Last Quarter Moon (8:46pm) Spica 3o south of the Moon 15 Mercury at greatest elongation East (19o) 16 Saturn 1.9o south of the Moon 20 Neptune 0.2o north of Mars 21 New Moon (12:14am) 22 Mercury 3o south of the Moon Venus 6o south of the Moon 23 Mars 4o south of the Moon 25 Uranus 0.6o south of the Moon 27 First Quarter Moon (3:48pm) 30 Aldebaran 1.2o south of the Moon

Times are listed in Eastern Australia Daylight Savings Time

Events Of Note

and it will only be outshone by the Moon, which will be near Jupiter on the night of January 8.

Saturn is rising in the early hours of the morning, one to two hours before twilight begins. Opening the year in Libra, Saturn moves into Scorpius by month’s end. Shining at magnitude 0.5, Saturn’s rings will be wide open, inclined at nearly 25o from our vantage point. � e 25-day-old Moon will be near Saturn on the morning of January 17 and the last week of January sees Saturn around 1o from the attractive double star Beta (β) Scorpii.

Pluto is in conjunction with the Sun on January 4 and returns to the morning sky in February.

Earth is at perihelion on January 4, at a distance of 147.1 million kilometres (0.98 au) from the Sun. � is marks the closest point to the Sun in Earth’s orbit.

� e Moon will be near Aldebaran on January 2 and 30 (the latter seeing an occultation for observers in Canada), Regulus on January 9, Spica on January 13, and Antares on January 17. �

Jupiter

Neptune

Uranus

Pluto

Saturn

Marchequinox

Sept.equinox

Decembersolstice

June solstice

Mars

Earth

Sun

Mercury

Venus


Sun, Moon and Planets

Jupiter’s Red Spot Transit, January 2015 (Universal Time)

These predictions assume the Red Spot is at Jovian System II longitude 207°. If it has moved elsewhere, it will transit 1.7 minutes late for every 1° of longitude greater than 207°, or 1.7 minutes early for every 1° less than 207°. Check SkyandTelescope.com/redspot for updates.

JANUARY1: 4:55 14:502: 0:46 10:42 20:373: 6:33 16:284: 2:25 12:19 22:155: 8:11 18:066: 4:02 13:57 23:537: 9:49 19:448: 5:40 15:359: 1:31 11:27 21:2210: 7:18 17:13

11: 3:09 13:04 23:0012: 8:56 18:5113: 4:47 14:4214: 0:38 10:33 20:2915: 6:25 16:2016: 2:16 12:11 22:0717: 8:02 17:5818: 3:54 13:49 23:4519: 9:40 19:3620: 5:31 15:2721: 1:23 11:18 21:14

22: 7:09 17:0523: 3:01 12:56 22:5224: 8:47 18:4325: 4:38 14:3426: 0:30 10:25 20:2127: 6:16 16:1228: 2:07 12:03 21:5929: 7:54 17:5030: 3:45 13:41 23:3731: 9:32 19:28

With Jupiter just weeks away from opposition, observers will have most of the night during January to follow Jupiter’s four Galilean moons.

The innermost of the four, Io, zips around Jupiter in 1.77 days, closely followed by Europa in 3.55 days. Ganymede takes 7.15 days, basically a week, and Callisto is almost leisurely with an orbital period of 16.69 days.

These moons are quite bright, ranging between 5th and 6th magnitude, and are easily seen in small telescopes. Room doesn’t permit us here to display the changing pattern they present, but it’s worth seeking out Jupiter each night to see how they’re moving. Can you identify which moon is which?

Satellites of Jupiter

January Right Ascension Declination Elongation Magnitudes Diameter Illumination Distance

Sun 1 18h 43.6m –23° 04' — –26.8 32' 32" — 0.983

31 20h 52.1m –17° 35' — –26.8 32' 28" — 0.985

Mercury 1 19h 42.8m –23° 30' 14° Ev –0.8 5.3" 91% 1.278

11 20h 44.9m –19° 22' 18° Ev –0.8 6.2" 71% 1.077

21 21h 15.8m –14° 46' 16° Ev +0.3 8.3" 29% 0.814

31 22h 44.3m –14° 28' 4° Mo +5.2 10.2" 1% 0.657

Venus 1 19h 55.3m –22° 11' 17° Ev –3.9 10.3" 96% 1.615

11 20h 47.6m –19° 28' 19° Ev –3.9 10.5" 95% 1.585

21 21h 37.8m –15° 50' 21° Ev –3.9 10.8" 94% 1.552

31 22h 25.8m –11° 28' 23° Ev –3.9 11.0" 92% 1.514

Mars 1 21h 34.4m –15° 37' 41° Ev +1.1 4.8" 94% 1.970

16 22h 19.7m –11° 28' 37° Ev +1.1 4.6" 95% 2.038

31 23h 03.4m –6° 56' 34° Ev +1.2 4.4" 96% 2.106

Jupiter 1 9h 36.8m +15° 08' 138° Mo –2.4 43.4" 100% 4.544

31 9h 24.2m +16° 15' 172° Mo –2.6 45.3" 100% 4.352

Saturn 1 15h 55.7m –18° 24' 39° Mo +0.6 15.5" 100% 10.695

31 16h 06.4m –18° 51' 67° Mo +0.5 16.1" 100% 10.297

Uranus 16 0h 47.5m +4° 23' 77° Ev +5.8 3.5" 100% 20.198

Neptune 16 22h 30.7m –10° 08' 40° Ev +7.9 2.2" 100% 30.712

Pluto 16 18h 57.7m –20° 38' 12° Mo +14.2 0.1" 100% 33.760

Sun and Planets, January 2015

The table at top gives each object’s right ascension and declination (equinox of date) at 0h Universal Time on selected dates, and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and equatorial diameter. (Saturn’s ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet’s disk illuminated by the Sun and the distance from Earth in astronomical units. (Based on the mean Earth–Sun distance, 1 au equals 149,597,870 kilometres. For other dates, see SkyandTelescope.com/almanac.

Moon, January 2015

PhasesFull Moon Jan. 5, 4:53 UT Last Quarter Jan. 13, 9:46 UTNew Moon Jan. 20, 13:14 UTFirst Quarter Jan. 27, 4:48 UT

DistancesApogee Jan. 9, 18h UT405,408 km diam. 29’ 28”Perigee Jan. 21, 20h UT359,645 km diam. 33’ 13”

LibrationsJan. 4 Max. libration (NE limb)Jan. 10 Min. libration (NW limb)Jan. 17 Max. libration (SW limb)Jan. 23 Min. libration (SE limb)Jan. 30 Max. libration (NE limb)

N

WE

S

ANTONÍN RÜKL


Celestial Calendar

Comet 15P/FinlayDate R.A. Dec. Delta r Elong. Mag. Const. (12hr UT) hh mm o ’ au au o

Jan 3 21 56.6 -12 45 1.406 0.982 44 9.1 CapJan 10 22 28.2 -9 00 1.394 0.999 46 9.2 AqrJan 17 22 59.5 -5 02 1.394 1.025 47 9.5 AqrJan 24 23 30.3 -0 59 1.406 1.061 49 9.8 PscJan 31 0 00.6 +3 01 1.431 1.104 50 10.2 Psc

Positions in these comet ephemerides have been calculated for 12hrs UT (11pm Eastern Australian Daylight Savings Time). “Delta” and “r” are the distances of the comet from Earth and the Sun in au.

Comet C/2012 K1 (PANSTARRS)Date R.A. Dec. Delta r Elong. Mag. Const. (12hr UT) hh mm o ’ au au o

Jan 3 0 08.5 -32 50 2.392 2.229 69 10.5 SclJan 10 0 07.2 -30 45 2.590 2.312 63 10.7 SclJan 17 0 07.2 -28 55 2.783 2.394 57 11.0 SclJan 24 0 08.3 -27 17 2.967 2.476 51 11.2 SclJan 31 0 10.1 -25 49 3.142 2.558 46 11.4 Scl

Comet C/2014 Q2 (Lovejoy)Date R.A. Dec. Delta r Elong. Mag. Const. (12hr UT) hh mm o ’ au au o

Jan 3 4 46.5 -13 36 0.479 1.351 132 8.9 EriJan 10 3 58.5 +3 46 0.476 1.324 127 8.8 TauJan 17 3 17.1 +19 29 0.535 1.304 115 9.0 AriJan 24 2 44.4 +30 55 0.637 1.293 104 9.4 AriJan 31 2 19.8 +38 45 0.762 1.291 94 9.7 And

The most interesting comet, especially for Australian observers, to grace our skies in

January is likely to be the new comet C/2014 Q2 (Lovejoy). � is comet, the � � h (excluding his early SOHO discoveries) found by well-known Queensland amateur astronomer Terry Lovejoy, was discovered on August 17 when little brighter than magnitude 15.

� e comet will arrive at perihelion (1.29 au from the Sun) on January 30 and will be a well-placed evening object for most of the month from Australian latitudes. As the New Year begins, comet Lovejoy moves from Lepus to Eridanus and on present indications will likely be around magnitude 9. Early in the second week of the month, it dri� s into neighbouring Taurus and is expected to brighten a little, staying at around magnitude 8.5 – 9 throughout the second week before fading by about one magnitude by the month’s end.

� e second half of January sees comet Lovejoy sinking lower into the evening sky as it passes into Aries around January 17 and thence through Triangulum and into Andromeda by the end of the month.

Retreating from its December 27 perihelion, comet 15P/Finlay should still be accessible on January evenings, albeit low in the western sky. As the month begins, it shi� s from Capricornus into Aquarius, reaching Pisces early in the second half of the month. It is expected to glow at around magnitude 9 early in the month, but will fade by one magnitude or thereabouts before January’s � nal days.

An Aussie Comet Summer David Seargent

David Seargent’s ebook Sungrazing Comets: Snowballs in the Furnace is available from Amazon.

Also drawing away from perihelion (last August 27), comet C/2012 K1 (PANSTARRS) may still be around magnitude 10.5 at New Year, although it too is expected to fade by at least one magnitude before the end of January. A slow-moving object in the constellation

of Sculptor throughout the month, it just reaches the border of Cetus as January closes.

Sun DiscThe Sun Disc from Astrovisuals represents a revolution in Sundial design. Unlike most other Sundials (which can generally be used only in one place) the Sun Disc can be used anywhere on Earth. Its rotatable disc even allows it to be adjusted for Daylight Saving Time!

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Alan Plummer observes from the Blue Mountains west of Sydney and can be contacted at [email protected]

As I write in September, the Mira variable R Reticuli is way down at 13th or 14th magnitude,

and by the time you read this, it will be rapidly brightening to 6th or 7th magnitude. R Reticuli, some 3,000 light-years distant with a period of 281 days, is yet another southern variable that needs more observers today, to continue a century and more of data.

One gets a sense of history with these stars having large data sets. Looking at the light curve in the AAVSO

R ReticuliAlan Plummer

Variable Star Maxima2015 Star Mag. RA Dec

hh mm o ’

Jan 12 T Sgr 8.0 19 16.2 -16 58Jan 14 S Gru 7.7 22 26.1 -48 26Jan 18 R Sgr 7.3 19 16.7 -19 18Jan 27 R Ret 7.6 4 33.5 -63 02Jan 28 T Cen 5.5 13 41.8 -33 36

Listed for each of these long-period variables are the expected date of peak brightness, the star’s typical visual magnitude at peak, and its right ascension and declination. The actual maximum may be brighter or fainter and early or late. COURTESY AAVSO (WWW.AAVSO.ORG).

Chart courtesy AAVSO and is approximately 4½o from north to south. Also plotted in the finder chart is the barred spiral NGC 1559 and the variable R Doradus (magnitude range 4.8 – 6.3, featured in the October 2010 issue). R Reticuli is located at 4h 33m 33s -63o 02.

76

81

ηR Ret

89

85

6888

6572

58 85

57

5261

55

5987

5046

NGC 1559

Dorado Reticulum North

R Dor

θ

γαδ

ι

International Data Base, observations began in India, with Norman Pogson, in 1863. He discovered several variables, did important cometary and minor planet work, and worked out the modern magnitude system.

After 20 or so years of Pogson’s intermittent observations, more consistent estimates next come from South Africa, with 15 years work by the Scottish immigrant Alexander Roberts. He left astronomy to go into Parliament to fight for racial equality, for which he is still much revered today in his adopted homeland.

Taking over from him was the Australian John Skjellerup who moved to South Africa and took up a passion for astronomy. You might remember the name from comet Grigg-Skjellerup and its rendezvous with the Giotto spacecraft in 1992. After him, there is a century of other observers and their stories, including the late New Zealand observer Albert Jones and the very much still-kicking New South Welshman Peter Williams. 7x or 10x50 binoculars are all you need to start. Join in and contribute!

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Ross Gould Double Star Notes

Revisiting the Great Hunter

Back in 2009 I wrote about some of the doubles in Orion. Six years later, here's a different choice of objects

from the many bright doubles in this constellation. Many of the Orion doubles are blue-white stars of spectral type B, as there are star-forming regions here. So for this month's column there are fewer coloured pairs than for some other regions of the heavens.

In northern Orion, nearly 5o northwest of Gamma (γ) Orionis, is the tight binary 14 Orionis (STT 98), discovered by Otto Struve in 1843. He discovered many very close pairs with the Poulkova 15-inch (38-cm) refractor, a more powerful telescope than the Dorpat 9.6-inch (24-cm) refractor his father had used in his earlier double star survey of the northern sky. Wilhelm Struve doubles are designated STF, or Σ on star charts; Otto Struve doubles are STT, or ΟΣ on star charts.

Since discovery, 14 Orionis has travelled around most of its 197-year orbit (see orbit diagram at right). Ernst Hartung, writing in his classic work Astronomical Objects for Southern Telescopes, noted that in the early 1960s, when the stars were slightly closer than at present, "200mm separates the stars cleanly", and called the colours "deep and pale yellow". With my 140-mm (5.5-inch) refractor I could detect elongation on 14 Orionis at 160x, although even 400x did not provide a clean split. 14 Orionis is nearly 200 light-years from us.

Only 6' south of 14 Orionis is the dim little pair STF 643, and a little way southeast from 14 Orionis is another Otto Struve pair, STT 100; viewed with a 140-mm refractor this was an uneven and fairly close pair at 160x, a little more power (200x) giving a better effect.

Some 6o south and just west from 14 Orionis is Rho (ρ) Orionis, a beautiful pair of orange and white stars, magnitudes 4.6 and 8.5 in brightness. Separated by 7”, my 140-mm refractor split them at 80x. A degree south from it is STT 517, a near-equal binary that’s very close — 400x could only show it elongated. I'd suggest a 25-cm (10-inch) telescope for a clean split at present. And a degree south-southwest from Rho Orionis is STF 652, a yellow star that

becomes a close, somewhat unequal pair at 160x.

Some 3.3o east of Rho Orionis, about halfway between Delta (δ) Orionis (in Orion’s belt) and Gamma (γ) Orionis to its north, is Psi2 (Ψ2) Orionis, also known as KNT 3, with STF 712 in the same field. George Knott, the discoverer of Psi2 Orionis, was a 'gentleman-scientist' of the Victorian era, who in the period from 1860 to 1873 was engaged in the measuring of double stars, with the bonus of making some discoveries. His telescope was a fine Clark refractor of 7.3-inches (18.6-cm) aperture, obtained from William Dawes, who I mention below.

These two doubles are only about 10' apart. STF 712 is an

Star Name Righthh mm

Declination

o '

Magnitudes Separation (arcseconds)

Position Angle(o)

Date of Measure

Spectrum

14 Ori (STT 98) 5 07.9 +8 30 5.8, 6.7 0.8" 295 2013 Am

STF 643 5 07.9 +8 24 9.6, 9.6 2.4" 124 2010 K2STT 100 5 10.0 +8 10 7.0, 10.4 3.5" 258 2011 F7STF 652 5 11.8 +1 02 6.3, 7.4 1.7" 180 2012 A+G2IIIRho Ori (STF

654)

5 13.3 +2 52 4.6, 8.5 6.8" 63 2011 K2II

STT 517 5 13.5 +1 58 6.8, 7.0 0.6" 242 2013 A5VSTF 712 5 26.5 +2 56 6.7, 8.6 3.1" 66 2012 B9.5VPsi2 Ori (KNT 3) 5 26.8 +3 06 4.6, 8.6 2.9" 327 1991 B2IVSTF 734 5 33.1 -1 43 AB 6.7, 8.2 1.7" 357 2008 B4V

" " AC 6.7, 8.4 29.4" 244 2012

BU 1049 " " CD 8.3, 9.2 0.5" 292 2002

STF 747 5 35.0 -6 00 4.7, 5.5 35.9" 226 2014 B0.5V,

B1V42 Ori (DA 4) 5 35.4 -4 50 4.6, 7.5 1.4" 208 1991 B1VIota Ori (STF 752)

5 35.4 -5 55 2.8, 7.7 11.6" 141 2012 O9III

STF 750 5 35.5 -4 22 6.4, 8.4 4.1" 60 2011 B2.5IVSTF 754 5 36.6 -6 04 5.7, 9.2 5.3" 288 2002 B1V

A Hunt for Doubles in Orion

Orion beckons you to explore its doubles.

Data from the Washington Double Star Catalogue.

East

North

-1

00

0.5

1

2015

1936

1976

-0.5

-0.5-1 0.5 1

2054

-1.5

2094

The apparent orbit of 14 Orionis


Ross Gould has been a long-time double star observer from the suburban skies of Canberra. He can be reached at [email protected].

easy, delicate, uneven, close pair at 80x with 140-mm aperture. Psi2 Orionis, a very uneven pair, appears apparently single at 80x, though at 160x it reveals a tiny companion very close in the steadier moments. At 400x it was steadily apparent. Psi2 Orionis is nearly unchanged from 1863 when it was discovered.

From here we'll go south to STF 734, 1o southwest of the middle star of Orion's belt, Epsilon (ε) Orionis. At � rst sight, with low power, a small telescope will show STF 734 as a wide pair of 6th and 8th magnitude stars. With the 180-mm refractor at 135x the primary became a delicate, uneven, close pair, just separated. An aperture of 100mm (4 inches) might be the minimum for this. � e fainter star is also double (BU 1049), but at 0.5" and with dim stars (8th and 9th magnitude), it will need good aperture to separate. So this is not a double-double that's as accessible as Epsilon Lyrae, or even Nu (ν) Scorpii.

And now for a trip along the Sword of Orion. Because Orion stands on his head from our vantage point in the Southern Hemisphere, the sword sticks up from the three bright stars of the Belt, so in this part of the world it's sometimes referred to as the handle of the Saucepan. However, domesticated or not, this part of Orion has some doubles worth visiting.

In the centre of the 3 main stars of the sword is the Great Orion Nebula, Messier 42, and within it the Trapezium, a gathering of four stars known as � eta1 (θ1) Orionis and easily seen with small telescopes. More di� cult are the stars E and F, much fainter companions to two of the Trapezium stars. On this occasion I'll only mention that group in passing as there's a huge amount of literature on it already.

Just over ½o north from the Trapezium, and involved in nebulous outliers of the Great Orion Nebula, is the di� cult double 42 Orionis (DA 4) in a group of stars. Discovered by the "eagle-eyed" William Dawes at the end of 1847 with a 6.3-inch (16-cm) refractor, it has become closer and therefore more di� cult over time. Dawes, whose name lives on in the 'Dawes' Limit' for resolving equal bright doubles, was one of the most careful measurers of known doubles in the early to mid-19th century, and he also discovered some doubles. He remarked of 42 Orionis, "� ough a somewhat di� cult object, from the closeness of the stars and their great di� erence of magnitude, it is surprising that it should not have been detected by either of the Herschels or by Struve."

At the time 42 Orionis was a little wider than it is now, being then at about 1.8" or 1.9" separation. It has since been closing slowly,

with the position angle also showing slow decrease. � ere is more scatter than usual in the measures of 42 Orionis, which suggests the di� culty of measuring the pair. To make it harder for some future orbit calculator, some of the measures in the latter 20th Century were either with inadequate telescope apertures, or have clear errors. As a result, the last reliable measures were by Hipparcos and Tycho in 1991, at 1.4" and PA 208o. Given the slow closing, it might now be at 1.3".

� e stars are about 3 magnitudes di� erent in brightness, and a large brightness di� erence always makes a close pair harder to see than the separation suggests. Hartung, � � y years ago, noted "the pair needs good de� nition to see the close companion with 10.5cm...".

I've seen it double, with di� culty, using my 140-mm refractor. Other observers have recently reported similarly di� cult sightings with that aperture. Based on di� raction theory, the � rst interspace between disc and ring occurs at 1.3" for an

aperture of 105-mm (the Rayleigh Criterion for that aperture), which would match Hartung's note, although the pair was very slightly wider then.

Only ½o north of 42 Orionis is the good double STF 750, magnitudes 6 and 8 at 4", a � ne object. Even at 62x with a 140-mm refractor it was a beautiful, little, uneven pair in a � eld of fairly bright stars.

At the other end of the sword, ½o south of M42 is the combination of Iota (ι) Orionis and STF 747 in the same � eld. With my 140-mm refractor at 62x, Iota Orionis was a bright white star with an easy 7th magnitude companion in a gathering of stars. Nearby to the southwest is the wide bright pair STF 747, also well seen at low power. Wide in the � eld to the east is STF 754, which bene� ts from rather more magni� cation — at 114x it was a bright white star with a tiny companion quite close. �

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Charles A. WoodExploring the Moon

Hunting for Lost BasinsCan you fi nd hints of these buried features?

rim of the Nectaris basin weakens and disappears in both directions.

� e Imbrium basin has inner rings similar to those in Orientale, but they are largely covered by thick layers of mare lavas, with only a few emergent mountains (including Mons Pico and Mons Piton) and mare ridges possibly marking a ring location. Imbrium shows that not all newly formed impact basins necessarily had perfect bull’s-eye patterns, and that subsequent events can bury and modify the original basin landscape.

Each large basin has its own peculiar history of formation and modi� cation. Mare Crisium is surrounded by a nearly continuous ring of massive mountains, but they don’t have the steep inward facing scarps of the Apennine and Atlas basin rims. Crisium, like Serenitatis and the other large basins, contains a hint of an inner ring that is detectable under low illumination. You can trace out subtle mare ridges that de� ne the buried inner rings in Crisium, Mare Serenitatis, and Mare Humorum.

Older basins have shallower, discontinuous rims; their lava-covered � oors are cratered by many subsequent impacts, and are lightened by rays and more extensive veneers of bright ejecta. Such old basins gradually disappear, making them an especially good observing challenge to � nd.

A small basin that most observers have seen but not recognised exhibits both a scarp-like rim and an unburied inner ring. Between Schiller and Zucchius in the Moon’s southwest quadrant is a relatively � at-� oored 335-kilometre basin that is o� en overlooked because of its more imposing neighbours. If you look closely, you’ll observe both a basin rim that extends more than three-quarters of the way around the central plain and a mountainous ridge that de� nes an inner ring. � is structure is the only example on the lunar nearside of a basin whose size and morphology is common on the lunar farside as well as on the rocky worlds Mercury and Mars.

It seems odd that many of the biggest landforms on the Moon are o� en the most di� cult to see. Massive impact

basins such as the ones containing Mare Imbrium and Mare Nectaris are easily recognised due to their roughly circular expanses of smooth lava and surrounding mountainous rim arcs. But older basins tend to disappear.

� e youngest and best-preserved lunar basin is Mare Orientale, but unfortunately its centre lies just over the western limb, so we only occasionally glimpse strongly oblique views of its outer mountainous rings and dark mare lavas. Spacecra� images show that the Orientale

basin has three or more concentric inner rings, like terraces in smaller crater walls, which surround a � attish central region. � e Orientale basin contains a small central mare, with additional leaks of lava along the inside scarps of its rings.

Scientists generally presume that most large lunar basins resembled Orientale when they formed, but that might not be the case. For example, the main rim of the relatively young Imbrium basin (which contains Mare Imbrium) is Montes Apenninus, which curves around just ¼ of the basin’s circumference, and appears to have formed that way. Similarly, the 90° arc of Rupes Altai along the southwest

Just beyond the elongated crater Schiller is the degraded remains of an ancient, unnamed impact basin fi rst noticed in 1959. NASA ⁄ GSFC ⁄ ARIZONA STATE UNIVERSITY

Schiller


Charles Wood (lpod.wikispaces.com) is co-author of the new book 21st Century Atlas of the Moon.

Another unappreciated basin has a very conspicuous central lava deposit, but a basin rim and inner ring that are di� cult to recognise. Grimaldi was named as a crater because the low ring that surrounds the central dark mare patch was mistaken for a crater rim. It’s actually the inner ring of an impact basin whose northern rim was largely destroyed, but whose southern rim is just visible as the boundary between an inner, light-hued, smooth area and the rougher terrain beyond.

Some basins are so old and heavily modi� ed that their existence is not completely certain. Since most nearside basins are named a� er the mare lavas they contain, it’s generally presumed that

every mare is contained within a basin. For the Serenitatis basin that’s likely because Montes Haemus is probably the last remnant of the rim, whereas the Serpentine Ridge and other mare ridges within the basin may de� ne its inner ring. But there is less evidence that impact basins underlie Mare Nubium, Mare Tranquillitatis, and Mare Fecunditatis. � e next time you observe the Moon, see if you can � nd evidence for basin rims or mare ridge inner rings for these maria.


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Grimaldi

Although named as a typical lunar crater, Grimaldi is the fl ooded central ring of a larger impact basin whose outer rim is degraded by later cratering events. NASA ⁄ GSFC ⁄ ARIZONA STATE UNIVERSITY


Sue FrenchTargets

Star BoundMany remarkable deep-sky objects lie near the variable star Algol.

1174. The former was discovered by William Herschel in 1786 and the latter by Lewis Swift in 1883. They were given separate entries in the original NGC (New General Catalogue of Nebulae and Clusters of Stars, 1888), because Swift’s position for NGC 1174 is about one minute of right ascension to the west of NGC 1186. But from Swift’s description, it’s apparent that the two objects are the same while his position is incorrect. This is made especially clear by Swift’s mention of a double star whose similarly bright components point toward his object from the northwest, which neatly fits NGC 1186 and h2171. The identity was first proposed in 1891 by Rudolf Spitaler and published in Astronomische Nachrichten.

On my way to NGC 1186, I bumped into IC 284. This galaxy has lower surface brightness than NGC 1186, but it’s still visible through my 130-mm scope at 37×. It’s a ghostly glow tilted north-northeast inside a skinny, 26′-tall triangle of three 8th- and 9th-magnitude stars. A close pair of faint stars sits 2½′ northwest. The galaxy shows better at 63×, covering about 1¼′ × ½′ with a small, subtly brighter core.

Folks with large telescopes might like to try for tiny PGC 11646, a 15th-magnitude galaxy nestled a mere 45″ west-southwest of IC 284, measured centre to centre.

Now we’ll move on to the Perseus Cluster (Abell 426), a collection of thousands of galaxies centred 230 million light-years away from us and 2.3° east-northeast of Algol on

Her Perseus joyns, her Foot his Shoulder bearsProud of the weight, and mixes with her Stars.

— Marcus Manilius, Astronomica

According to Greek myth, the brave hero Perseus rescued Andromeda from the terrible sea monster Cetus

and claimed the fair maiden for his bride. At night we still see the couple wedded in the night sky, with Andromeda warming her feet against her husband.

Where foot and shoulder meet, we find the seldom-mentioned star group NGC 956. It’s not always plotted in the same place, nor listed with the same size. John Herschel discovered the group in 1831 and described it as a moderately rich cluster with two or three bright stars and about 20 diminutive stars of magnitude 13 to 15. The coordinates Herschel gave are for one of the bright stars (SAO 38098, magnitude 9.1), not for the centre of the group. Some sources place the centre of the NGC 956 northeast of that star, others southwest. What do you think Herschel saw?

Here’s my visual impression of NGC 956 through my 130-mm (5.1-inch) refractor. At 23×, six 9th- to 11th-magnitude stars form a 7′ U, open toward the west. At 37× there are nine stars that lie along the U, two within it, and one to its north. Of the three 9th-magnitude gems decorating the U, the southernmost is gold, the westernmost

glows orange, and the remaining one is Herschel’s star. At 117× I see a loose collection of 22 suns with a generous assortment of magnitudes.

Whatever John Herschel saw, NGC 956 isn’t considered a true cluster now. In a 2008 paper in Astronomische Nachrichten, Polish astronomers Gracjan Maciejewski and Andrzej Niedzielski determined that NGC 956 is a chance alignment of physically unrelated stars. The size and centre coordinates for NGC 956 listed in the table on the facing page come from this paper.

Let’s swing our scopes farther eastward to visit some of the many galaxies that inhabit Perseus. We’ll start with NGC 1186, which is located 1.9° north-northwest of Algol (β Persei). In my 130-mm refractor at 48×, the galaxy is a faint smudge leaning west-northwest, with a superposed star near the centre. The double star h2171 hovers 5′ northwest of NGC 1186, with components weighing in at magnitudes 10.7 and 11.3. At 63× the galaxy displays a 1½′-long, oval core surrounded by a tenuous fringe that spans about 2½′ × ¾′. At 117× most of the fringe is invisible, but it’s easier to ascertain that the superposed star is southwest of the galaxy’s centre. With my 10-inch (25-cm) reflector at 171×, I see another overlaid star, this one perched on the southern side of the galaxy’s eastern end.

NGC 1186 is sometimes called NGC

NGC 1186

h2171

IC 284 PGC 11646

SLOAN DIGITAL SKY SURVEY (2)


Galaxies, a Double Star, and a Cluster in Perseus and AndromedaObject Mag(v) SB Size RA Dec.

NGC 956 Asterism 8.9 12.0′ 2h 32.3m +44° 34′

NGC 1186 Galaxy 11.4 3.2 × 1.2′ 3h 05.5m +42° 50′

IC 284 Galaxy 11.5 4.1′ × 2.1′ 3h 06.2m +42° 22′

NGC 1275 Galaxy 11.9 2.2′ × 1.7′ 3h 19.8m +41° 31′

20 Persei Double star 5.0, 9.7 13.9″ 2h 53.7m +38° 20′

Angular sizes and separations are from recent catalogues. Visually, an object’s size is often smaller than the catalogued value and varies according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox 2000.0.

IC 239

1003

1023

1058

1161

1186

IC 2841275

M34

956

Algol

14

1620

π

ρ

β

κ

ω

A N D R O M E D A

P E R S E U S

2h 30m

+44°

2h 40m2h 50m3h 00m3h 20m

+42°

+40°

+38°Star magnitudes

7 86543

1175

1186

IC 284

1198

12501260

1265

12721275

1281

1282

1293

1294

IC 292

IC 312

βAlgol

P E R S E U S

3h 05m+43°

3h 10m3h 15m3h 20m

+42°

+41° Star

mag

nitu

des

5

4

3

6

78910


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the sky. Its brightest member is NGC 1275, also called Perseus A — a designation that flags its copious emission at radio wavelengths. Powered by a supermassive black hole, the galaxy is also a vigorous X-ray source. Features interpreted as sound waves spread hundreds of thousands of light-years outward from this black hole. The pitch is far below human hearing, a profoundly deep B-flat that’s 57 octaves below middle C (AS&T: May/June 2013, page 26).

NGC 1275 is a small, round, faint galaxy that grows brighter toward the interior, as viewed with my 105-mm (4.1-inch) refractor at 87×. NGC 1272 (magnitude 11.8) is barely visible 5.2′ west-southwest, and a 12th-magnitude star lies between the two galaxies. NGC 1272 is much easier to see at 127×. It appears a little smaller and more uniform in surface brightness than its neighbour. Its broad core is only slightly brighter than its fringe. At 153× NGC 1278 (mag. 12.4) makes an appearance, yet it’s only intermittently visible with averted vision as a small smudge.

Through my 10-inch (25-cm) reflector at 166×, NGC 1275 is oval east-southeast to

west-northwest and much brighter in the middle, whereas NGC 1272 is round with a marginally brighter heart. NGC 1278 is smaller but has higher surface brightness than NGC 1272. Its east-west oval intensifies toward a bright core. Several additional galaxies share the field of view. NGC 1273 (mag. 13.2) is fairly easy and a bit oval, whereas NGC 1277 (mag. 13.5) is a petite, fuzzy spot just northwest of NGC 1278. PGC 12405 (mag. 14.2) is quite faint and rests upon a little triangle of very dim stars. This galaxy is sometimes incorrectly identified as IC 1907. With averted vision, NGC 1274 (mag. 14.0) materialises halfway between NGC 1278 and NGC 1273.

West of NGC 1272, three more galaxies join the tableau. NGC 1270 (mag. 13.1) is a small oval tipped north-northeast that brightens inward, while to its west, NGC 1267 (mag. 13.1) is more obvious. NGC 1267 is round and seems to have a considerably brighter centre, a perception that’s probably enhanced by its superposed star. An incomplete oval of very faint stars, open to the northwest, holds NGC 1267 just within

its western side, and NGC 1270 is one of the spots in its eastern side. Only 1.3′ north of NGC 1267, NGC 1268 (mag. 13.4) is an ashen fuzzspot. At 213× an extremely faint star twinkles at its southern edge.

NGC 1268 is the lone spiral galaxy in our quick and localised tour of the Perseus Cluster, although others exist. The main body of the cluster spans more than 3° on the sky and contains dozens of galaxies that are visible through moderate to large backyard telescopes.

We’ll bring our journey to a close with a brighter and more colourful object, the lovely double star 20 Persei. This is a very unequal pair, with the primary star shining at magnitude 5.0 and its companion at 9.7. In my 130-mm refractor at 37×, the bright star glows yellow-white, and its attendant is a little spark of light to its west-southwest. At 63× the stars are widely separated, and the secondary looks reddish orange to me. What colours do you see. ✦

Targets

The brightest galaxies in the densest section of the Perseus Galaxy Cluster are labeled here; not all the labeled galaxies are described in the text. Labels starting with P represent galaxies’s designations in the Principal Galaxy Catalogue, labels starting with U are from the Uppsala General Catalogue, and labels with no prefix are from the New General Catalogue. R. JAY GABANY

1281

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Sue French welcomes your comments at [email protected].


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Ken Hewitt-WhiteGoing Deep

Fuzzy Duos Inside the CircletFive galaxy pairs inhabit this well-known asterism in Pisces.

The Circlet of Pisces (setting a� er midnight in December when this issue reaches

subscribers) is outlined by Lambda (λ), Iota (ι), � eta (θ), Gamma (γ), and Kappa (κ) Piscium. To that quintet of 4th- and 5th-magnitude stars I like to add similarly bright 7 and 19 Piscium on the west and east sides, respectively, to form the 7°-wide � gure outlined on the chart below. � e star 19 Piscium is interesting in its own right; it’s a carbon star (deep red) and an irregular, low-amplitude variable — hence its alternate name TX Piscium.

� e extended Circlet contains perhaps two dozen galaxies within range of my 17.5-inch (44-cm) f/4.5 Dobsonian on a moonless country night. � e targets are all small, but

some of them form close pairs that display considerable character at around 300×. Let’s assess these fuzzy duos in a clockwise tour around the asterism, beginning with a challenging pair just north of 5.7-magnitude 16 Piscium, which lies 1.5° west of Lambda Piscium.

� e glare from 16 Piscium nearly swamps NGC 7714 and NGC 7715 just 4′ north-northwest of the star. Images show that these spiral galaxies are gravitationally interacting to produce distorted arms and prominent starburst regions. In my scope, 12.5-magnitude NGC 7714 is a dim patch accompanied by a 14th-magnitude star less than 1′ southwest. A closer look reveals another star so near the galaxy’s centre that it

masquerades as a brilliant nucleus. My averted vision detects extended nebulosity southeast of the bright centre, giving the object a cometlike appearance. Averted vision also helps me locate severely deformed, 14.2-magnitude NGC 7715 barely 2′ eastward. Telescopically, it’s a narrow haze, elongated east-northeast by west-southwest, that points slightly south of its brighter neighbour.

From 19 Piscium it’s a 1¼° sweep west-northwestward to NGC 7731 and NGC 7732, only 1.4′ apart. A face-on spiral, 12.8-magnitude NGC 7731 is a somewhat ragged oval blob, slanted northeast-southwest, with a bright, almost starlike middle. An 11.6-magnitude star lies about 1′ east of it. A similar distance south of the

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The galaxy pairs and double stars described in this article are labelled in yellow.


star is a celestial ghost: the nearly edge-on, 13.8-magnitude galaxy NGC 7732. Even with the star to guide me, I consider this tenuous wisp, elongated east-west, surprisingly hard to spot. A less challenging edge-on lies ¼° north-northwest. Like NGC 7732, IC 5014 is a cigar-shaped mass oriented east-west, but it brightens gently toward the middle and presents a sharp edge along its southern flank. A 15th-magnitude star flickers alongside that flank, south-southwest of the midpoint, while a pair of brighter stars shine northeast of centre.

At Iota Piscium, we drop southwestward 1.3° to a scatter of faint fuzzies dominated by the nondescript S0 galaxies NGC 7704 and NGC 7706,

and fades at the ends. Two 14th-magnitude stars lie almost parallel to the galaxy’s eastern flank.

Next, we hop over Theta Piscium at the top of the Circlet and head southwest to 7 Piscium. From there we turn south-southeastward for 20′ to a 10th-magnitude star, then push a similar distance eastward until we encounter UGC 12547 and UGC 12548 (PGC 71204 and PGC 71209, respectively). These little fellows, a mere 2.5′ apart, are totally unalike. UGC 12548 is a 14th-magnitude edge-on specimen that yields to averted vision as a subtly mottled streak with a broad central bulge. Southwest of it, fainter UGC 12547 is a face-on, two-arm spiral that at best registers as a vaguely oval patch. I can also detect minute 16th-magnitude PGC 71224 less than 6′ east-southeast of the pair.

Our final waypoint is Gamma Piscium, the brightest star in the Circlet. From Gamma Piscium we hike 3° eastward to the middle of the asterism, where the face-on spirals NGC 7679 and NGC 7682 (magnitude 12.6 and 13.2, respectively) lie 4.3′ apart. NGC 7682 is round and diffuse, while its partner is condensed with a bright centre. These galaxies exhibit some evidence of mutual attraction; images show an arm of NGC 7679 swelling in the direction of NGC 7682. East and northeast of the pair are two more NGC galaxies: 13.2-magnitude NGC 7685 and 13.4-magnitude NGC 7687, while to the southeast is 15th-magnitude PGC 71578. This roundish glow is attended 3′ westward by a 1′-long row of three stars — a miniature Orion’s Belt!

Finally, take a crack at Burnham 1222 (β1222) only 6′ northwest of NGC 7679. Its 10th-magnitude components, just 1.4″ apart, resolve between 222× and 285×, depending on the seeing. Much easier is colourful Struve 3009 (Σ3009, magnitude 6.9 and 8.8, 7.1″ separation) located 1.9° east-northeast of Gamma Piscium. Another fine catch, Struve 3019 (Σ3019, 7.8, 8.4, 10.9″), is 1.3° south-southeast of Theta Piscium.

S&T contributing editor Ken Hewitt-White observes faint fuzzies under the dark skies of British Columbia, Canada.

magnitude 13.4 and 13.2, respectively. NGC 7706 appears diffusely oval with a faint star on its southwest periphery. NGC 7704, 5′ southwest, is similar, with a dim star near its southeast edge. In the space between that galaxy and the 12th-magnitude star 3′ west of it, I can usually confirm ultra-tiny PGC 214966.

Nudging ¼° farther west nets little 13.9-magnitude NGC 7696. And 6′ south of NGC 7704 is the pale glow of 14.4-magnitude NGC 7705. From NGC 7706, a ¼° shift north-northeast sweeps up the edge-on, 14th-magnitude galaxy UGC 12689 (PGC 71831). This strongly elongated object, oriented northwest-southeast, is broadly brighter across the middle

The interacting spiral galaxies NGC 7714 and 7715, collectively known as Arp 284, are almost overwhelmed by the glare of the foreground star 16 Piscium. The field of view is 7.3′ wide.

The asymmetric spiral NGC 7679 and the striking barred spiral NGC 7682 constitute entry number 216 in the Arp Atlas of Peculiar Galaxies. SLOAN DIGITAL

SKY SURVEY (2)

7682

7679

7715 7714

In the Moon’s Shadow



JAY ANDERSON

The Moon’s dark umbral shadow will sweep across Earth’s surface once every

year from 2015 through 2017. � is means that anyone lucky enough to � nd oneself in the lunar shadow’s path, or who wants to travel, will witness that most spectacular of naked-eye astronomical phenomena: a total eclipse of the Sun. Although three total eclipses in three consecutive years is not unusual — it last happened in 2008–2010 — the eclipses forming this trio are remarkably di� erent from one another.

March 20, 2015� e stormy North Atlantic in late winter is hardly a popular tourist destination. Nevertheless, the track of the March 20, 2015 total eclipse passes right through the region and will likely draw many eclipse chasers. Although the path of totality is quite wide (about 462 kilometres), the eclipse su� ers from two important disadvantages: lack of land in the path and poor weather prospects.

As the map at right shows, the eclipse path forms a backward C-shaped curve beginning south of Greenland and ending at the North Pole. Unfortunately, Iceland lies just

outside the broad path that counts the Faroe Islands and Svalbard as the only two land options. � e surprisingly green Faroes are a small group of 18 islands northwest of Scotland. Svalbard is a Norwegian archipelago located midway between Norway and the North Pole. Both destinations o� er two or more minutes of totality provided that the Sun is not obliterated behind thick clouds.

� e Faroes are embedded in the main storm track across the North Atlantic and so have a well-deserved reputation for clouds. At Vágar Airport, on the west side of the islands, cloud cover averages 75%, and the average number of sunshine hours for March is a meagre 24% of the maximum possible. Eclipse seekers will have to remain mobile, looking for openings in the clouds on eclipse day, or they’ll need to head for high ground to surmount the fog that commonly envelops the archipelago in the morning.

Longyearbyen, the leading community on Svalbard’s Spitsbergen Island, o� ers better weather prospects, with an average cloudiness of 55%. Moisture is limited in the colder Svalbard climate and the terrain that

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dominates the community helps to break up and dissipate clouds. Eclipse sites within Longyearbyen must be chosen carefully so that the Sun is not blocked at the critical moment, but Spitsbergen scenery can provide spectacular settings for photographers.

If ever an eclipse begged for an aerial rendezvous, 2015 is it. Eclipse chaser Xavier Jubier is organising

A Trio of

EclipsesThe next three years each o� er a chance to travel

and view one of nature’s greatest spectacles.

Bottom left: Coauthor Fred Espenak and his wife Pat view totality from Libya on March 29, 2006. Top: A high-dynamic-range image of the eclipse reveals fi ne details in the corona. Centre: A mosaic records the various eclipse phases.

The central line of the March 20, 2015 total solar eclipse crosses only a few points of land, all in the Faroe Islands and Svalbard.

FRED ESPENAK

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one such � ight, and he estimates at least a dozen more are being planned. Such � ights are expensive, but airplanes can � y above most eclipse-obscuring clouds.

March 9, 2016Nearly one year later and halfway around the planet, the central track of the 2016 eclipse crosses the equator, passing through a decidedly warmer climate. Although the shadow path is narrower than it was in 2015, it’s more than twice as long and stretches one-third of the way around Earth. But nature’s seeming perversity is at work again because most of the track crosses island-free ocean. � e 2016 eclipse can only be seen on terra � rma from Indonesia and a few tiny Paci� c islands.

Nevertheless, the two to four minutes of totality coupled with the allure of Indonesia and the Paci� c are factors in this eclipse’s favour. � e eclipse track begins some 1,400 kilometres west of Sumatra and quickly heads due east, where it crosses the island. Continuing onward, the central path traverses southern Borneo, Sulawesi, and the Moluccas, including Halmahera, as it slowly curves to the northeast. Stretching across the vast Paci� c, the path passes near Wake and Midway Islands and ends about 1,800 kilometres northeast of the Hawaiian Islands.

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Above: A picturesque temple sits in Beratan Lake on the Indonesian island of Bali. The central path of the March 9, 2016 eclipse won’t make landfall on Bali, but it’s not far away for eclipse chasers. Bottom left: The 2016 eclipse central line crosses mostly ocean, but makes landfall across several major islands in Indonesia.

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SAYOGA / ©ISTOCKPHOTO.COM


� e weather prospects are a major concern. Indonesia’s humid and o� en cloudy climate o� ers daunting statistics for eclipse expeditions. � e country lies beneath the Intertropical Convergence Zone (ITCZ), where trade winds from the Southern and Northern Hemispheres collide, serving up a daily menu of showers and thunder-storms. Western Indonesia in particular is one of the cloudiest places on Earth.

An observer in eastern Indonesia — Sulawesi or the Moluccas — will be on the edges of the ITCZ, where cloud coverages are about 20% less than the 75% to 85% in Borneo and Sumatra. Sulawesi and the Moluccas are rugged, so the best sites on these islands are in the mountain valleys, where the air is forced to descend, warming and drying in the process. Mountains can also shade the eclipse site for an hour or two a� er sunrise, slowing the daily temperature rise and delaying the start of convective buildups, an advantage that will be reinforced by the growing shade of the approaching lunar shadow.

Ocean prospects are much more promising, because a ship’s mobility gives a much higher probability of success. Access to the eastern end of the path from the Hawaiian Islands is also generating eclipse-cruise and aerial-rendezvous possibilities.

August 21, 2017Although no dedicated eclipse chaser likes to pass up the opportunity to bask in the Sun’s coronal glory during totality, many would consider the 2015 and 2016 eclipses to be warm-up acts for the main event: August 21, 2017. � e path of totality returns to the continental United States for the � rst time since 1979 a� er a lapse of 38 years.

� e eclipse track runs diagonally from the Paci� c Northwest to the southern East Coast, spanning 4,000 kilometres and crossing signi� cant portions of a dozen states. You’d have to go back nearly a century, to June 8, 1918, to � nd a total eclipse crossing a comparable swath of U.S. real estate. � e central duration of totality is two or more minutes along the path, peaking at 2 minutes 40 seconds near the Illinois-Kentucky border. Not only that, the eclipse takes place during the height of summer vacation season, giving millions of families the chance to witness totality.

As if that weren’t enough good news, the weather prospects along the track are excellent. August is a notably sunny time of year, when the peak of the thunderstorm season has passed. A quick look at the cloud climatology reveals a fairly simple pattern: America is cloudy in the

Ocean prospects are much more promising, because a ship's mobility gives a much higher probability of success.

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mountains and cloudy east of the Mississippi River. Within that broad-scale pattern, there are many local variations and attractive destinations to tempt eclipse chasers. � e choice eclipse sites are in Oregon and Idaho followed closely by Wyoming and Nebraska. � e Rocky Mountains are why those states have the best weather prospects.

Over Washington and Oregon, the up-and-down topography brings a cloudy climatology on windward slopes and sunny skies in the valleys. East of the Mississippi, the Appalachians do much the same, though the e� ect is much smaller, because humid air can arrive from both east and west, courtesy of the Gulf of Mexico and Atlantic.

� e eclipse central line comes ashore within spitting distance of a small park called Fishing Rock on the south edge

This image from the Japanese MTSAT-2 weather satellite shows the cloud coverage over the Indonesian archipelago on March 9, 2013 at eclipse time. The infrared signal is shown in blue tones, the visible in yellows. White clouds are thick and high, yellow clouds are at low levels. High-level thin clouds are shades of blue. NERC SATELLITE RECEIVING STATION / DUNDEE UNIV. / WWW.SAT.DUNDEE.AC.UK

The central line of the great U.S. eclipse of August 21, 2017 will be within a one- or two-day drive of almost anyone living in or visiting the contiguous 48 states.

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of Lincoln Beach, Oregon — a scenic, rocky point accessed by a narrow forest trail. It’s a fitting place to start the eclipse, because Lincoln Beach was also under the Moon’s shadow for the February 26, 1979 total eclipse. The waterfront is noted for its fog, but it’s not a serious problem because the mist usually only manages to reach a short distance inland on the narrow coastal plain.

A winding highway out of Lincoln Beach takes the eclipse traveller across the Oregon Coast Range to Corvallis, Oregon, and the Willamette Valley. Located some 15 kilometres north of the central line, Salem has an average cloud cover that is 20% lower than spots on the coast. Go a little farther east, across the much higher Cascade Range to the Columbia Plateau, and the weather gets even better. Madras, Oregon, lying only 10 kilometres south of the shadow axis, has the distinction of having the least August cloudiness along the eclipse track. At Redmond, Oregon, at the southern limit, 20 years of observations at the airport show an average August cloud cover of only 8%.

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But Madras has competition — in the next valley, over the Blue Mountains. The highway goes to Interstate 84, the Snake River, and the Oregon-Idaho border, where satellite and surface observations reveal a cloud climatology nearly as good as Madras. A little farther along the track, however, you’ll encounter the rugged peaks and valleys of the Rocky Mountains, where the topographic see-saw leads to even more pronounced cloud cover. Average cloud cover reaches 60% on the Salmon River Mountains of Idaho and more than 70% on the Wind River Range in Wyoming, but drops back to about 50% in the valley communities of Idaho Falls, Idaho, and Riverton, Wyoming.

At Casper, Wyoming, the Rockies have been left behind and the Great Plains are in sight. Casper is the only sizeable city that lies smack on the central line, and it’s a fine location — only about 10% cloud cover at eclipse time according to airport observations at lower elevations. Because of this, the Astronomical League has chosen Casper to host its national convention in the days just preceding the eclipse.

The only fly in the ointment is the possibility of bushfire smoke on eclipse day. The city often experiences a thin haze from fires elsewhere in the Western states. But smoke from bushfires could be a small problem just about anywhere in the West.

Nebraska and Kansas offer wide-open spaces and no cloud-making terrain to avoid, though the occasional August thunderstorm might present an avoidable problem. For the whimsical, check out Carhenge near Alliance, Nebraska, a short 10 kilometres north of the central line with a favourable dip in the average cloudiness to boot. A good highway network, unimpeded by mountain ranges, allows for a quick eclipse-day escape if needed. Cloud cover generally averages between 20% and 40% on the Plains according to station observations, but more according to the satellites (which are typically about 20% to 30% higher than ground observations).

East of the Mississippi, cloud cover begins a steady climb, fed by moisture from the Gulf of Mexico and encouraged by Appalachian peaks.

This graph from satellite data plots the average cloud coverage along the path of totality for the 2017 eclipse. Use it to make relative comparison of sites, because satellite observations are typically 20% to 30% higher than what observers see from the ground. SOURCE: JAY ANDERSON / NOAA


Astronomer Fred Espenak (NASA/Goddard Space Flight Center) masters two eclipse websites (eclipse.gsfc.nasa.gov and www.MrEclipse.com) and is a coauthor of Totality – Eclipses of the Sun. Meteorologist Jay Anderson has written about eclipse climatology since 1979 and has journeyed to confirm his predictions in person. More detailed climate and weather information can be found at www.eclipser.ca.

Surface observations show that cloudiness rises from around 25% in Missouri to more than 50% in Tennessee and the Carolinas. At Carbondale, Illinois, cloud coverage eases up a bit in the Big Muddy River watershed — a propitious omen, perhaps. Carbondale could be called America’s Eclipse City, because it lies at the junction of the 2017 and 2024 eclipse paths. A little to the east, Hopkinsville, Kentucky is making plans for a big influx of visitors due to its proximity to the point of greatest eclipse, the instant when the axis of the Moon’s shadow passes closest to Earth’s centre.

The lunar shadow leaves U.S. shores near Charleston, South Carolina,

putting historic Fort Sumter 10 kilometres inside the south limit. The central line is a little farther north, close to Buck Hall Recreation Area, overlooking marshy islands and the Atlantic. The 2017 eclipse could not be better designed for the U.S.: coast-to-coast, north to south — and pretty decent summer weather to boot.

2017 Strategy: MobilityBecause of the convenient network of highways, the 2017 eclipse offers an excellent opportunity to hedge one’s bets. Despite the favourable climatological outlook, clouds still occur some of the time everywhere along the path. The key to avoiding them is mobility. It’s fine to choose a

Carbondale, Illinois is one of the luckiest towns for eclipse aficionados. This downtown location, on South Illinois Avenue, will see a 2 min 36 sec total eclipse on August 21, 2017 and a 4 min 09 sec total eclipse on April 8, 2024.

Carhenge, located near Alliance, Nebraska, is a not-to-scale replica of England’s Stonehenge. Carhenge lies just 10 kilometres from the path of totality. Left: The path of totality makes landfall at this spot in Fishing Point, Oregon. The axis of the eclipse lies on this side of the first promontory.

JAY ANDERSON (3)

viewing location years in advance, but be prepared to abandon it if the forecast looks bad the day before the event. There’s still time to pack the car and head for a location offering a better forecast. With an early start, you can cover hundreds of kilometres to reach a destination with clear skies. Mobility might increase your eclipse viewing odds by 10%, but it’s still no guarantee, especially if August 21st hosts a major storm system covering much of the nation. Consider too the backup travel plan — the next total solar eclipse in the U.S. is only seven years later.

Because of the convenient network of highways, the 2017 eclipse offers an excellent opportunity to hedge one's bets.


Gary SeronikTelescope Workshop

Here’s a simple method for aligning your telescope’s optics without lasers or other gadgets.

No-Tools Collimation

Most readers know that the only way to get every last drop of optical performance from a

reflecting telescope is to have the scope in good collimation. When we want to tune up the collimation we usually reach for devices such as a Cheshire eyepiece or laser collimator. But in spite of their utility and usefulness, many of these collimation tools have shortcomings. For example, most collimation devices require that the centre of the primary mirror be accurately marked in some way. That’s fine for Newtonians, but not for Schmidt-Cassegrains and Maksutovs. Luckily, there’s an easy way of achieving optical alignment that doesn’t require any of these tools.

The method outlined here is essentially a star test, but with a twist. It can be performed in the dark and only requires a clear night sky. Begin by centring a star that’s around 2nd magnitude in your scope’s field of view. For Dobsonian users in the north,

Polaris is the ideal choice — it’s the right brightness and essentially stationary. For readers here in the south, choose a bright star in the southern half of the sky as the next best alternative. If your telescope has a tracking mount, you have more options.

Next, choose an eyepiece that provides the right amount of magnification. The ideal power is around 25× per inch of aperture, which is what Dick Suiter recommends in his classic book, Star Testing Astronomical Telescopes (Willmann-Bell, 2009). Thus, you should use around 200× for an 8-inch (20-cm) scope. A simple, math-free way to get 25× per inch of aperture is to choose an eyepiece with a focal length that matches the f/ratio of your scope. For example, if your scope is f/6, use a 6-mm eyepiece. If it’s f/10, a 10-mm eyepiece is right.

Begin by adjusting the focus in or out until the star appears as a disk of light with a dark hole near its centre

As explained in the accompanying text, the offset central hole in this defocused star image indicates that the reflector is out of collimation.

Step 1: By re-aiming the scope, move the defocused star image around the field until its image appears the most concentric.

Step 2: By adjusting the scope’s main collimation screws, move the defocused image to the centre of the field.

Step 3: To further refine collimation, adjust the scope’s focus to produce a smaller out-of-focus image and repeat steps 1 and 2.

To enjoy the sharpest views of the Moon, planets, and stars, the optics in your telescope must be accurately collimated. S&T: SEAN WALKER

(the hole is the secondary mirror’s silhouette). If your scope is out of collimation, that hole will not appear centred in the illuminated disk, and thus your primary mirror’s zone of optimum performance isn’t centred in the eyepiece field. Your collimation task


This collimation method works very well, but there are a couple of provisos.

Contributing editor Gary Seronik is an experienced telescope maker. He can be contacted through his website, www.garyseronik.com.

is to move that zone to the centre of the field.

Begin this process by moving the out-of-focus star around the field of view by re-aiming the scope slightly. Eventually you’ll find the location where the dark hole in the star image is centred, or most nearly so — that’s the sweet spot. Then, by using your scope’s collimation screws only, move the defocused star from that position to the centre of the eyepiece field.

If you’re working with a Newtonian reflector, it helps to have someone else make collimation adjustments to the primary mirror while you look in the

eyepiece and give instructions. If you’re collimating a Schmidt-Cassegrain, you can probably do the necessary adjustments to the secondary mirror yourself. Proceed slowly and methodically.

Once you’ve moved the defocused star to the centre of the eyepiece field, adjust the scope’s focus to shrink the star image down into a smaller circle of light — this ups the collimation sensitivity. Repeat the previous steps, then focus down tighter still, and repeat again. After one or two iterations, you will be looking at a star image that’s just slightly out of focus, which is where this method is most accurate. Finally, when you think you’re done, centre the star, defocus it, then slowly refocus while paying close attention to the dark hole at the centre of the star image. If your scope is well collimated, the bright rings in the defocused star image will collapse down concentrically around the shrinking black centre.

This method works very well, but there are a couple of provisos. First, if you’re collimating a Newtonian, you have to make sure your secondary mirror is already correctly positioned. (See the February/March 2013 issue, page 80, for details.) Second, collimation accuracy depends on atmospheric seeing conditions, but then too so does your scope’s optimum performance. Finally, the star-test collimation method works best for a quick touch-up after the scope has already been roughly aligned — but most of the time that’s all the collimation that’s needed.

Give it a try. I’m confident that with a little practice, it’ll take you only a few moments to fine-tune your scope’s optical alignment in the field. ✦

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Image Processing

MICHAEL UNSOLD

There’s little doubt that digital SLR cameras have opened the hobby of astro-imaging to the

masses. Never before has it been so easy (and relatively inexpensive) to take great shots of twilight conjunctions, Milky Way nightscapes, and even deep-sky vistas. But most

DSLRs and even some CCD cameras aren’t perfect detectors. Although they take exquisite daylight images, many produce “banding” and line noise that show up in low-light conditions.

Fortunately, banding and line artefacts are easy to correct using modern astronomical image-

processing programs. Follow these steps to transform your noisy images into clean, smooth data.

Band and line noise, sometimes referred to as horizontal and vertical banding noise (HVBN), are common artefacts in images of the night sky taken with DSLR and some CCD

Although virtually all astrophotos from recent years were taken with digital cameras, the images often su� er from banding and line noise, which can compromise an otherwise excellent image. Author and software engineer Michael Unsold describes his innovative technique for correcting this problem using his program ImagesPlus. He used this software to remove the broadbanding artefacts from the left image of NGC 7000, which was taken with a modifi ed Canon EOS 40D. Unsold’s processing led to the smooth result at right. Unless otherwise noted, all images are courtesy of the author. CHUCK VAUGHN (2)

Eliminating Band & Line Noise

Here’s a technique that removes common artefacts from DSLR and CCD images.


Left: The small-scale line noise seen in this close-up image of the Horsehead Nebula often appears in DSLR images taken at high ISO settings. Right: Although the lines are easily corrected using a simple algorithm, bright objects such as stars have added additional artefacts in the image. AJAY TALWAR (2)

cameras. The problem has multiple sources, some as a result of your camera’s sensor readout, others due to its analogue-to-digital conversion and signal amplification using high ISO settings (gain settings on video cameras work in a similar way). Banding can also come from electrical interference from adjacent equipment on the same power circuit. In all cases, these issues can detract from an otherwise fine image.

Band and line noise exist in most images taken with a DSLR, even daylight photos, though they aren’t often visible. This is because HVBN resides in the low-signal area of your images, such as the shadows. In daylight imagery, light levels are easily sufficient to overwhelm that signal. Unfortunately for astrophotographers, light from deep-sky objects is extremely faint compared to subjects illuminated by our Sun, so astro-imagers need to “stretch” the low-end signal to reveal most targets, such as the Milky Way over a landscape or the faint ion tail of a comet. This stretching unfortunately also amplifies band and line noise.

with colour and monochrome cameras, I’ve devised a technique that removes line and band noise from an image without loss of small-scale detail.

Simple Correction TheoryThe key to removing band and line noise is to first recognise that these signals are periodic and repeat at specific frequencies. As such, they are best corrected using the Fourier transform function, a mathematical tool that allows you to target specific frequencies and remove them from digital images.

The problem is that many desirable features in our astrophotos, particularly the ever-present stars, also occupy some of the same frequencies as the lines and bands. So if you globally apply line or band suppression using a Fourier transform to an image with stars, then you’ll not only remove the lines and bands, you’ll also introduce undesirable artefacts around the stars — particularly new dark bands that emanate from any bright stars or galaxy nuclei in the photo.

Targeted Processing: Line NoiseThe best approach to correcting band and line noise is to split the image into two separate files in ImagesPlus as Blair MacDonald describes in detail in the August/September issue (page 88);

abridged star-splitting directions appear below. By splitting the image onto two images, one with only the stars and the other with the lines, bands, and other subject matter (we’ll call this the “subject image”), we can target just the artefacts while avoiding the introduction of additional ones. The split is done in a lossless state so that you get the same image as you started with when you merge the split star and object images. You then create the final photo by merging the corrected image with the star image. You can correct band and line noise in ImagesPlus using either “raw,” unprocessed data or a final image.

To split the stars and subjects into two images, begin with your calibrated and combined image in ImagesPlus, and select Special Functions / Mask Tools / Feature Mask © from the pull-down menu. A new window opens, where you can adjust the star radius size, threshold, and Mask Area Size until you’re satisfied that you’ve selected all the stars and other bright features in the image. Make sure that your selection includes the bright nuclei of galaxies, bright planetary nebulae, or comet heads, since each can add artefacts to your result if not properly selected.

Once you’re satisfied with your selection, click the Split Stars button at the bottom right of the window. In a few moments, you’ll have two images:

The problem is that many desirable features in our astrophotos also occupy some of the same frequencies as the lines and bands.

Line noise appears as a periodic pattern of narrow vertical or sometimes horizontal lines that become more pronounced as you enhance an image. Banding is similar, though with much wider “stripes” than what appears with line noise. These stripes often have a colour bias in colour images, with some bands in blue, green, or red.

Popular methods for correcting these artefacts attempt to mask or blur their effects but do not actually remove them from your data. These techniques can also soften image detail, which reduces the final quality and sharpness of your image. Using my program ImagesPlus, which I wrote specifically for processing astronomical images taken


Image Processing

one with only the star data, and the other with your nebulae, galaxies, and other subject matter in addition to the bands and lines you want to correct.

ImagesPlus uses two separate tools to correct lines and bands, and since both artefacts don’t always appear in every image, let’s begin by correcting an image with line noise. Click on the subject image and open the Smooth Sharpen / Line Enhancement and Suppression Tool to remove the � ne vertical-line pattern. A dialogue window opens, with a few important options. If your photo su� ers from vertical or horizontal line noise,

select which type you want to address in the Eliminate section. Next you’ll change the Vertical Height to the maximum setting of 121 in the Line Detection Window Size in Pixels section. Now you want to adjust the Horizontal Width parameter and click the “Apply” button. I suggest starting with the lowest setting � rst.

In a minute or so, the process completes and displays your result. If lines are still visible in your image, increase the Horizontal Width parameter and repeat the process until they are no longer visible in your image.

Removing Bands If your image su� ers from wide coloured banding, split the image into stars and subject images. Next, select Smooth Sharpen / Band Suppression from the pull-down menu. A small dialogue window opens, where you can select the Enable Vertical Band Suppression or the horizontal option. Depending on which you choose, the top Suppress slider controls vertical banding, while the second slider adjusts for horizontal bands. Both begin at the “Most” setting at right, so reduce the number slightly and wait a minute for the program to process your image. I suggest lowering the setting in increments of 5 to narrow down what works best for your particular photo.

Once you’ve split the stars and other bright objects into a separate image, click on the image with your target object and open the Line Suppression & Enhancement tool. Simply select the Horizontal Lines, Vertical Lines, or both from the Eliminate section of the tool, and adjust the height and width options until the lines disappear from your photo.

Identify and separate the stars and other bright objects from the fainter signals in your image using the Feature Mask © tool (far right). Move the Star Radius slider to the right to increase the amount of stars in your selection, and expand the area of your mask by moving the Masked Area Size slider to the right, producing the black masks in the image at near right.


Contributing editor Ted Forte enjoys the dark skies of his backyard observatory outside of Sierra Vista, Arizona. His column � e Backyard Astronomer appears monthly in the Sierra Vista Herald.

When you’re happy with the result, click the “Done” button, and you can proceed to recombine the star image with your nebulae, galaxy, or nightscape photo.

Select the Special Functions / Combine Images Using / Blend Mode, Opacity, and Mask. � is time two windows open — the Combine Images Setup window, where you � rst can title the combined result, and the Combine Images window. � e Combine Images Setup window allows you to title your

merged result, then click OK. In a moment, a new image appears, and the Combine Images window displays a list with the working titles of your image and stars-only photos. Make sure your corrected image is at the bottom of the image stack by clicking the up or down arrows. Next, change the Blend Mode of the star image from Normal to Merge Split. In a moment both images will appear as a combined result. Click the Flatten button, and then save your � nal result.

You can apply band and line correction to any colour or monochrome image, and the correction can help with most astronomical images to rid them of repeating noise. Many high-speed video cameras used for planetary imaging o� en su� er from line noise, too, and you can quickly address it with this technique. Tools such as these are o� en the � nal key to raising your images to the next level of pro� ciency.

Michael Unsold has grown ImagesPlus to a mature astronomical imaging program for DSLR and CCD imagers alike. Explore its other features at www.mlunsold.com.

Wide banding can be addressed using the Band Suppression tool in ImagesPlus. Click on your subject image then open the tool and select the Enable Vertical Band Suppression (or horizontal if necessary). Pull the Suppress Vertical (or Horizontal) sliders left to reduce the e� ect on your image until you match the width of the bands.

When you’ve corrected the line or band noise in your subject image (lower left), recombine the stars (upper left) with your subject using the Blend Mode, Opacity, and Masks tool (far right).

Make sure your star image is at the top of the stack, then change its Blend Mode to Merge Split. Click the Flatten button to produce a fi ne result (centre).

A Walk with the Sky


This project aims to protect the night sky by turning people’s eyes to the stars.

A Star Walk for Everyone


Light pollution is every astronomer’s enemy. Professionals and amateurs alike suffer from the

growing abundance of artificial light. To cut light pollution down or simply keep it from spreading further, public awareness is essential.

But people don’t always respond well to cries of doom and gloom. Instead, we need to persuade them gently. In our experience, there is no better way to inspire public support than to lift people’s gazes up toward the starry sky. Even those who are only marginally interested in astronomy are wowed when they see the Milky Way in all its splendour for the first time.

This is the awe our team seeks to harness. We are Project Nightflight, a small team of astrophotographers who have been working for years to present the marvels of the night sky to the public in our images. Our photographs of celestial objects always focus on the beauty of the universe, whether we shoot deep-sky fields or nightscapes. We like to draw people’s attention to the natural wonders of the night sky, instead of raising the warning finger against light pollution.

Our latest approach to increasing public awareness was to design an astronomical “edutainment” venue near a major city. We came up with the idea of a permanent star walk: a nature trail with a focus on astronomy that introduces the splendour of the night sky at a beginner’s level. With information panels posted along the route and located at an easily accessible distance from a major metro area, the star walk has proved to be a successful astronomy outreach program.

KAROLINE MRAZEK & ERWIN MATYS

TWILIGHT WALK Despite looming clouds, the Grossmugl Star Walk’s inauguration attracted a large group of curious skygazers. Above the scene, Jupiter, Castor, and Pollux shine brightly in the fading twilight. PROJECT

NIGHTFLIGHT



Step by StepWe chose to build this installation in Grossmugl, a small town of about 1,500 inhabitants that lies only a 30-minute drive north from Austria’s capital, Vienna. Grossmugl was the ideal candidate for us because its night sky is still largely intact, frequently o� ering

limiting magnitudes of 6 or better.In May 2013 we presented our idea for

a star walk and a detailed dra� for its implementation to the mayor of this small town. He was enthusiastic about it and a few months later brought our plan before the town council, which approved it. During the winter months we were busy planning the details of the trail and designing the panels. We kept the topics on the displays deliberately simple to make them suitable for the general public and for children.

As soon as the snow melted the construction work began. � e local construction team set up the signposts and mounted the displays. � e signposts are simple wooden beams rammed into the ground, with the all-weather aluminium panels attached. � ese 2-mm-thick aluminium panels are reinforced with wooden multilayer boards to give them better stability. We designed everything to be maintenance-free, to keep upkeep e� orts at a minimum.

One year later, on May 24, 2014, the star walk o� cially opened. Roughly 100 visitors came to participate in the inaugural walk, despite storm clouds looming on the horizon in all directions.

A Walk in the Dark� e Grossmugl Star Walk is a 1.5-kilometre-long nature trail that’s open 24/7 all year round and doesn’t require booking a reservation. It starts in the village centre, where a trail of white stars painted on the pavement leads visitors into the surrounding � elds and meadows. Along the trail stand nine panels that take visitors slowly on a

journey into the night sky. � e panels explain how easy it is to see constellations, star colours, and even galaxies with one’s own eye, and each panel includes a simple illustration that shows the aspect of naked-eye observation covered in the text. � e displays describe basic astronomy facts both in German and English. At each station a short audio in German is also available via QR code for download with smartphones.

� e star walk is designed as a twilight walk. � e large print on the panels is clearly readable without illumination even in nautical twilight, when stars of third magnitude are visible. � e � rst station introduces the general idea of the walk. A set of pictograms encourages visitors to use red � ashlights during the walk and to dim all lights so that their eyes can gradually adjust to the dark. � e second display informs people that bright street lamps, illuminated shop signs, excessive parking-lot lighting, and other bright outdoor lights are the reason why they can no longer see faint stars and the Milky Way in densely populated areas. � is display also explains that the right choice of lamps and lamp shielding can make the starry sky visible again. From the third display onward, the illustrations and the short texts describe celestial wonders that visitors can observe with the unaided eye.

Here and there we added discussions of some interesting facts that the nonstargazer might be unaware of: how long it takes the human eye to adapt to the dark, the di� erent colours of stars, the range of star brightnesses (and the

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GrossmuglThe Project Behind the Star WalkThe organization that spearheaded the Grossmugl star walk, Project Nightfl ight, is an association based in Austria known o� cially as Verein zur Darstellung und Erhaltung des Sternenhimmels, which translates as “Association for the Presentation and Conservation of the Starry Sky.” The project is active worldwide and unites experienced, active astrophotographers in their endeavour to bring the unspoiled starry sky to others with their pictures and to promote the conservation of the dark sky as an environmental resource.

SHORT AND SWEET Signposts along the star walk introduce visitors to various visual observing targets, from the Milky Way to satellites. The panels also discuss topics such as light pollution and dark adaptation (the latter appears above). PROJECT NIGHTFLIGHT

THE STAR ROUTE Visitors encounter nine stations on their 1.5-kilometre walk from the village centre to the ancient Leeberg burial mound. S&T:

LEAH TISCIONE; SOURCE:

GOOGLE MAPS

Intro to thestar walk

The Milky Way & other galaxies

Protecting the starry sky

Dark adaptation

Star colours

Star brightnesses

Stellar motions across the sky

Conclusion & invitation to linger

How to recognise satellites

A Walk with the Sky

fact that bright stars are not necessarily close to Earth), the frequency of artificial satellites zipping across the sky, how the apparent motion of the stars across the sky works, and that some galaxies — including our home galaxy, the dazzling Milky Way — are visible to the naked eye. The panels explain all this in basic terms so that even visitors with no initial astronomical knowledge can enjoy their guided gaze up into the night sky.

The star walk ends at Star Meadow, a field of about one acre dedicated to skywatching all year round. It contains an Iron Age burial mound called the Leeberg tumulus, which was erected roughly 2,500 years ago. We chose this site as the walk’s culmination to give visitors an Earth-based reminder of the ancient beauty of the sky. It’s also a gathering point for astronomical events throughout the year.

After finishing the walk, visitors can continue star-gazing here with their dark-adapted eyes, perhaps sitting at a bench that locals call the Stars’ Rest. Then they can return along the same path back to Grossmugl.

Go FurtherAlready on the day of its opening the star walk showed its first positive effects: some village residents had improved their outdoor lights for the occasion. The municipality is also planning to change street lights to full cut-off lamps in the near future.

The Grossmugl Star Walk was a nonprofit project funded by a local corporate sponsor and carried by the enthusiasm of all involved, not least by the dedicated drive of the town’s mayor. We hope that the star walk idea will inspire many amateur astronomers, stargazers, and perhaps even officials across the world to build similar venues dedicated to the night sky. For those who want to know more about the first permanent star walk installation, an illustrated and more detailed description is available for download in PDF format on our website in the Tests & Tools section. We intend the Grossmugl Star Walk to serve as a blueprint for similar projects and invite you to be creative: think of new and innovative ways to bring the night sky closer to the broader public’s attention. ✦

Karoline Mrazek and Erwin Matys are founding members of Project Nightflight. Between them they have more than 40 years of astrophotography experience. Check out their images and learn more at www.project-nightflight.net.

STARRY SKY At Star Meadow, the star walk ends with an ancient burial mound and a fine view of the Milky Way. Only half an hour’s drive away from Austria’s capital, Vienna, the night sky is still largely intact here. PROJECT NIGHTFLIGHT



Gallery

The 2014 David Malin AwardsLast July, as part of the Central West Astronomical Society’s annual Astrofest (held in Parkes), their astrophotography competition, known as the David Malin Awards, was once again held. On the next few pages we present the Category winners and Honourable mentions.

CATEGORY WINNERS

WINNER: PAUL HAESECATEGORY: Deep Sky “Dust and Gas”CITATION: "I think this is the best true-colour image of the Orion Nebula I have seen for a long time. It has everything. The basics are well covered by a realistic-looking colour balance and the dynamic range, which makes the heart of the nebula look brighter than everything else, which is as it should be. But the other things are right too, including the delicate, faint nebulosity that fi lls the fi eld and the careful handling of the bright stars, which don't dominate the image. Fantastic!"

OVERALL

WIN

NER


WINNER: PAUL HAESECATEGORY: Solar System — Wide-Field “Prominence”CITATION: "This is a stunning image in all respects, and shows the active Sun and large prominence on the limb. A lot of e� ort and specialised knowledge goes into making images of this quality, and this is a superb example of an arcane art."

WINNER: STEFAN BUDACATEGORY: Solar System — Hires “Mars 2014” CITATION: "Intriguing composition of a series of excellent images of Mars over several months, all of them showing fi ne resolution and the obvious change in the diameter of the planet with distance. Excellent!"

WINNER: PHIL HARTTheme — "The Moon” “Marine Moonset” CITATION: "This is a striking image that has a quite painterly quality. The careful cropping and a soft and gentle light, makes the photograph look like an art work."


Gallery

WINNER: PHIL HARTCATEGORY: Wide-Field “Dusty Heart of the Milky Way” CITATION: "This is a perfectly simple rendition of the Milky Way using an o� -the-shelf camera and a standard 50mm lens. However, the quality of the result is outstanding, especially the colour balance and stunning detail. Beautiful!"

WINNER: DAVID FITZ-HENRYPHOTO EDITOR'S CHOICE JUDGED BY STEVE GROVE “The Horsehead and Flame Nebulae” CITATION: "This image contains all the elements of an intriguing photograph — splendour, mystery and drama. It's one that takes the average observer into what is truly the beauty of deep space."


WINNER: PETER WARDCATEGORY: Animated Sequences — Scientific “Shine On”CITATION: "Very beautiful and informative high resolution, time-lapse footage of the Sun in H-alpha light, carefully edited and very effectively set to music by Pink Floyd."

WINNER: ALEX CHERNEYCATEGORY: Animated Sequences — Aesthetic “Dance of the Dishes”CITATION: "Very smoothly edited and professional-looking sequences of the ATCA telescopes at work, and I especially like the fish-eye sequences of the dishes nodding at each other as they scan the Milky Way. Great stuff!"

ANIMATED SEQUENCES There were two winning entries for Animated Sequences. Their videos can be viewed at www.parkes.atnf.csiro.au/news_events/astrofest/awards/

HONOURABLE MENTIONS DEEP SKY

The Witch Head NebulaSTEFAN BUDA

47 Tucanae STEVE CROUCH

The Trifid MARCUS DAVIES

Rho Ophiuchi RegionPHIL HART

The Eagle and the Pillars of Creation ERIK MONTEITH


Gallery

HONOURABLE MENTIONS WIDE-FIELD

Pathway of LightJULIE FLETCHER

Venus and Zodiacal GlowGRAHAME KELAHER

Flow GREG GIBBS

Convergence MICHAEL GOHLondon Bridge StarsSTEPHEN HUMPLEBY


HONOURABLE MENTIONS SOLAR SYSTEM — HIRES

Colours of CopernicusSTEFAN BUDA

Annular Eclipse — Baily’s BeadsRUSSELL COCKMAN

Moonfl owersBRATISLAV CURCIC

PopcornDAVID HOUGH

White Light Sunspot AR11967DAVID HOUGH


Gallery

Partial Solar Eclipse Sunset Series STEPHEN MUDGE

HONOURABLE MENTIONS SOLAR SYSTEM — WIDE-FIELD

Partial Solar Eclipse Sunset Series STEPHEN MUDGE

Full Disk H-Alpha SolDAVID HOUGH

A Date with the Sun ROBERT KAUFMAN

Partial Solar Eclipse SettingANDREW WALL

Selenic Construction PETER WARD


HONOURABLE MENTIONS THEME — "THE MOON"

Luna in the Clouds SAEED SALIMPOUR

St. Kilda Moonset PHIL HART

Moonrise over Darling Harbour BRAD LE BROCQUE

Greenland MoonJUDITH CONNING

Scorpio in Luna’s Halo SAEED SALIMPOUR


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Focal Point Bert Probst

Winning Converts to the Cause

We like to believe we are converting the world to amateur astronomy when

we hear the “Wow!” at our star parties. Truth be told, most of those “wows” are forgotten by the next morning or as soon as the person discovers the e� ort required to progress from an appreciative spectator to an active participant. � e e� ort involves self-motivated reading and study to bring order to the apparent random chaos of the night sky and to learn about the instruments we use.

� e weather we must contend with to view the Milky Way under a cold winter sky may also be a negative factor. As for our instruments, we o� en overemphasise them to the point that our audiences may feel they must own a telescope or binoculars as an initiation fee to our hobby. Remember, naked-eye observing can be very rewarding and should be encouraged. � is is particularly true in our age of Iridium � ares and the International Space Station.

For many people I encounter at star parties, the spirit is willing but the � esh is weak. Yes, we see lots of telescopes at star parties and know many friends with operating telescopes, but the number of scopes in basements and attics gathering dust far exceeds the number gathering starlight. How many times have you heard, “Yeah, I have a telescope, but a� er looking at the Moon, Saturn, Venus, and Jupiter, what else is there to see?”

To overcome these obstacles one must have an inherent curiosity about the night sky and be intrigued by questions such as: What’s up there? How far can I see? Why does it change from season to season? Where are the boundaries of the universe, if there are boundaries? Where do shooting stars come from? Why do we see only one side of the Moon? Are we alone?

One must also have an attraction to seemingly insoluble mysteries, such as: How many stars are there? How can glaciers be miles thick? Can it really be

It takes e� ort to turn interested people into full-blown amateur astronomers.

Naked-eye observing can be very rewarding and should be encouraged.

never receive feedback; such is the plight of a missionary. And we must accept the fact that no matter how many beautiful views are up there, many folks are simply not intrigued with the night sky.

Example and patience are vital when handling fragile neophytes. Remember at star parties and lectures, you are there to help guide your audience, not to impress them with your knowledge. Just do a quick � ashback to your own early days when you thought the precession of the equinox was a parade of some political group.

Take heart; there are born amateur astronomers out there waiting for you to ignite the � ame. Go do it! �

true that no two snow� akes are alike? � ere are many amateur

astronomers born with the inherent attributes of curiosity and wonderment, but they have not awakened to their full potential to enjoy a lifetime of satisfaction from our hobby. � is is where outreachers come in. We need to help people discover their full potential. With dedicated e� ort, example, and patience, you can kindle that inherent spark into a � aming amateur astronomer. � is may not happen o� en, but when it does it is oh so gratifying. And sometimes you may

Retired NASA engineer Bert Probst has been an amateur astronomer for more than 40 years. He presents astronomy classes at the Ellicottville, New York Memorial Library and conducts astronomy events at Acadia National Park in Maine.

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