August First Light Newsletter1 message

August, 2014 Issue 122

AlachuaAstronomyClub.org

BREAKING NEWS -- ROSETTA HAS JUSTARRIVED AT COMET 67/P

Initiated in late 1993 by Europe and theUSA, and launched in 2004, theInternational Rosetta Mission is an historicfirst: Send a spacecraft to chase and orbita comet, ride along as the comet plungessun ward to learn how a frozen comettransforms by the Sun's warmth, anddispatch a controlled lander to make insitu measurements and make first imagesfrom a comet's surface.

Ten years later Rosetta has now

North Central Florida'sAmateur Astronomy Club

Serving Alachua County since 1987

Member Member

Astronomical League

MemberNASA Night Sky Network

arrived at Comet 67P/Churyumov-Gerasimenko and just successfully madeorbit today, 2014 August 6!Unfortunately, global events haveforeshadowed this memorable event andnews media have largely ignored thisimpressive space mission.

The Rosetta comet mission may be thebeginning of a story that will tell moreabout us -- both about our origins andevolution. (Hence, its name "rosetta" forthe black basalt stone with inscriptionsgiving the first clues to decipheringEgyptian hieroglyphics.) Pictures receivedover past weeks are remarkable with thelatest in the past 24 hours showingawesome and incredible detail includingviews that show the comet is a connectedbinary object rotating as a unit in 12hours.

For images see http://www.esa.int/spaceinimages/Missions/Rosetta Example Image (Aug. 6 above). Shows a smooth region at base of comet from 130 km (80 mi) with 2.4 meter per pixelresolution and a range of features, including boulders,craters and steep cliffs. Note: Comet 67/Pmoves in an eccentric orbit (eccentricity 0.64) with a 6.45 yearperiod that takes it from just outsideJupiter's orbit (5.7 AU) to just outsideEarth's orbit (1.2 AU).

Events are being streamed by ESA at:http://sci.esa.int/rosetta/54457-rosetta-arrives-at-comet-67pc-g---follow-the-event-live

For more on this mission see:http://www.esa.int/Our_Activities/Space_Science/Rosettahttp://rosetta.jpl.nasa.gov/

Howard L. CohenEmeritus Assoc. Professor of AstronomyDepartment of AstronomyUniversity of Florida

AAC Member photo:

Anyone see the glorious pairing of Venusand Jupiter this morning (2016 Aug. 18)?

Except when Mars is occasionally brighterthan Jupiter, these two planets are thebrightest nighttime sky objects (discountingthe Moon).

My quick photo does not do the scenejustice (below). Photo taken at 6:25 a.m.EDT when they were 10 degrees above thebrightening ENE horizon. Separation was0.3 degrees or slightly more than a halfmoon diameter. This was a bit wider thantheir closest approach (0.2 degrees), butthat happened several hours earlier (beforethey rose). My pinkie easily hid both.

Neither planet was at greatest brilliancy butstill spectacular: Venus was at magnitude-3.85, Jupiter -1.80. (This made Venus 6.6times brighter looking than Jupiter.)

If you didn’t get up to see this, you misseda beautiful sight. Tomorrow morning theirseparation will have increased to 1-1/4degrees. This should still make a neatscene.

Howard L Cohen

Droughts, Floods and the Earth's Gravity,

by the GRACE of NASASpace Place article by Dr. Ethan Siegel

When you think about gravitation here on Earth, you very likely think about how constant it is, at 9.8 m/s2 (32 ft/s2).Only, that's not quite right. Depending on how thick the Earth's crust is, whether you're slightly closer to or fartherfrom the Earth's center, or what the density of the material beneath you is, you'll experience slight variations inEarth's gravity as large as 0.2%, something you'd need to account for if you were a pendulum-clock-maker.

But surprisingly, the amount of water content stored on land in the Earth actually changes the gravity field of whereyou are by a significant, measurable amount. Over land, water is stored in lakes, rivers, aquifers, soil moisture, snowand glaciers. Even a change of just a few centimeters in the water table of an area can be clearly discerned by ourbest space-borne mission: NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites.

Since its 2002 launch, GRACE has seen the water-table-equivalent of the United States (and the rest of the world)change significantly over that time. Groundwater supplies are vital for agriculture and provide half of the world'sdrinking water. Yet GRACE has seen California's central valley and the southern high plains rapidly deplete theirgroundwater reserves, endangering a significant portion of the nation's food supply. Meanwhile, the upper MissouriRiver Basin undefined recently home to severe flooding undefined continues to see its water table rise.

NASA's GRACE satellites are the only pieces of equipment currently capable of making these global, precisionmeasurements, providing our best knowledge for mitigating these terrestrial changes. Thanks to GRACE, we've beenable to quantify the water loss of the Colorado River Basin (65 cubic kilometers), add months to the lead-time watermanagers have for flood prediction, and better predict the impacts of droughts worldwide. As NASA scientistMatthew Rodell says, "Without GRACE we would have no routine, global measurements of changes in groundwateravailability. Other satellites can’t do it, and ground-based monitoring is inadequate." Even though the GRACEsatellites are nearing the end of their lives, the GRACE Follow-On satellites will be launched in 2017, providing uswith this valuable data far into the future. Although the climate is surely changing, it's water availability, not sealevel rise, that's the largest near-term danger, and the most important aspect we can work to understand!

Learn more about NASA’s GRACE mission here: http://www.nasa.gov/mission_pages/Grace/

Kids can learn all about launching objects into Earth’s orbit by shooting a (digital) cannonball on NASA’s SpacePlace website. Check it out at: http://spaceplace.nasa.gov/how-orbits-work/

Image credit: NASA Earth Observatory image by Jesse Allen, using GRACE data provide courtesy of JayFamigleitti, University of California Irvine and Matthew Rodell, NASA Goddard Space Flight Center. Caption byHolli Riebeek.

Kids can test their knowledge about the Sun at NASA’s Space Place:

http://spaceplace.nasa.gov/solar-tricktionary/

SchoolsMike Toomey

Outreach & Star PartiesIvo Rabell

In September we have oneyouth event scheduled. TheO2BKids Parent NightOut on Friday, September 26,2014. Guests arrive at 7:30p.m. Telescope set up beginsat 6:30 p.m. at 6680 W.Newberry Road, Gainesville,

FL 32605. Please note that AAC volunteerscan access the observing field through a

First I want to thank theKelly’s for doing a terrific jobfeeding and hosting 12members and 6 guests at theirhome. They suppliedsandwiches, cokes, beer, wine,etc. We all appreciated them

for their hospitality.

Even though I was right when predicting the

gate located off N.W. 9th Blvd. (a blocknorth of RedLobster). Additional details andinformation can be found on the club'swebsite under Events Calendar.Thanks, Mike

Upcoming Events

For full details of events, please visit ourwebsite's events calendar.

September Public Meeting

Tuesday, Sept. 9, 2014, 7-9 p.m.Florida Museum of Natural HistoryUniversity of Florida Cultural Plaza

3215 Hull RoadGainesville, FL 32611-2710

Join us for an interesting evening when ourspeaker, Dr. Haywood Smith a member ofthe Astronomy Department at theUniversity of Florida will present TheDiscovery of Neptune.

International Observe the Moon Night

Saturday, Sept. 6, 2014, 7 p.m.Behind Easton Newberry Sports Complex

24880 N.W 16th AvenueNewberry, FL 32660

Please join the AAC in observing our nearestcelestial neighbor. Open to the public and

telescopes provided.

New Members

Welcome to new AAC members!

John Snyder (Joined June 26)

Mark Kelly (Joined Jule 27)

Patrick Norby (Joined July 9)

Pater Karahalios (Joined July 26)

sky would clear at around 9:15 pm, it didnot last. Within 30 minutes, except for asmall portion of the southern sky, the cloudstook over. We had no rain but a lot of sheetlightning to the east of us. Only fourmembers set up their telescopes orcameras.

Howard Cohen took beautiful images ofMilky Way including Scorpius andSagittarius. Images are forthcoming. TerrySmiljanich set up his Tom Dobbins telescopeand we all got to look at a few openclusters, globular clusters in both Scorpiusand Sagittarius. He also showed Albireo inCygnus. Lisa Eager showed Saturn with itsmoon Titan and what I though was a terrificRing Nebula. After spending a long timesetting up his terrific telescope, the easternand western sky clouded up and Paul Coiawas not able to star align his telescope to beable to track. I can’t wait until we have aclear sky, star party and be able to lookthrough his telescope.

We all got to see a few satellites sweepingacross the sky and a meteor going fromEast to West, which Terry said, had a bluetail before it disintegrated. Even though theweather hampered viewing after a shorttime I believe everyone had a great timeand some of us didn’t leave until close to11:00 pm.I want to personally thank all members atlast night’s Kelly’s Star Party.

Mark KellyRon SpinkMarie LucasTerry SmiljanichHoward and Marian CohenAmir and Mary AbdullahPaul Coia and Laura WrightLisa EagerMargarita Quinteros

I also want to thank two guest students thatI invited, Matt Given and Morgan Gates.

Cheers,Ivo RabellStar Party Coordinator

President's ReportAndy Howell

First Light Newsletter EditorLaura Wright

VOLUNTEER FOR 2015

THE CLUB NEEDS YOU during 2015. We urgently needvolunteers to fill the followingpositions during 2015:

Vice President

Secretary

Treasurer

To express your interest, email and tell us whichposition:

volunteer@alachuaastronomyclub.org

Other opportunities include

Telescopes Coordinator

Programs Coordinator

Public Outreach Coordinator

To express your interest, emailand tell us which position:

volunteer@alachuaastronomyclub.org

We were very sorry to loseone of our long timemembers, Dr. Neil White inAugust. He presented to theClub on August 14, 2012 atalk on "Orit Determination:

How I Found Your Ellipse". He alsodonated a telescope to the Club that hehad used when he was a youngstergrowing up in Michigan. He will bemissed. Part of his obituary is belowfrom Gainesville.com.

Gainesville - Dr. Neil Lawrence White,69, resident of Gainesville, Florida, diedMonday, August 11, 2014, in the NorthFlorida Regional Medical Center,following an ongoing illness.

Dr. White was born on January 25, 1945in Midland, Michigan, to the late Halbertand Vivian Spear White. He received hisBachelors Degree from Michigan StateUniversity, and then his PhD inMathematics from Harvard University.In 1973, Dr. White began his career inthe Math Department at the Universityof Florida, where he spent the next 35years, until his retirement in 2008. Hisinterests were many, and varied, amember of the Gainesville Stamp Club,the Gainesville Bridge Club, the AlachuaAstronomy Club and the Gator VolleyballAttack Club; he was a volunteer forGuardian Ad Litem and the FloridaMuseum of Natural History.

A Memorial Service will be held onSunday, September 7, 2014 at 3:00P.M., in the Florida Museum of NaturalHistory, 3215 Hull Road, Gainesville. Inlieu of flowers, contributions toward theNeil White Excellence in Teaching awardmay be sent to the Department ofMathematics, PO Box 118105, Univ ofFL, Gainesville 32611-8105. Checksshould be made out to the Dept. ofMathematics. Please visit his memorialpage atwww.williamsthomasfuneralhome.com.

Enjoy exploring the night sky.

Regards,Laura

Night-Sky Observing during August / September

Meteor Showers: August’s Perseids

by Andy Howell

The annual meteor shower known as the Perseids came to their peak during August 10-14, peaking in the pre-dawnhours of August 12. Unfortunately, the moon was near full and weather did not cooperate with visual observers.However, an automated video camera in my Gainesville backyard was able to capture 46 meteors on the evening ofAugust 11/12. Approximately half of these were Perseids. At one point during the night, a trio of meteors werecaptured within a single 8.5 second interval (below).

A meteor trio, evening of Aug 11/12

Alpha Tau (Aldebaran) is the star in the upper right.

NIRCam Education & Outreach Newsletter July-August, 2014

by Larry Lebofsky and Don McCarthy (University of Arizona) Used with permission.

The Nighttime Sky

Below is a fisheye view of the sky at 10 pm on August 1. The annual path of the Sun, the ecliptic (shown as theyellow line toward the bottom of the image), is low in the sky. It is winter when the Sun passes through theseconstellations! Below we highlight four prominent constellations that are higher in the sky during our summerevenings: Hercules, the Roman mythological hero; Lyra, the lyre (similar to a small harp); Cygnus, the swan; andAquila, the eagle. Three of these constellations (Lyra, Cygnus, and Aquila) form the familiar asterism, the SummerTriangle.

Fisheye view of sky on September 1, 2014 at 10pm DST

(click to enlarge)

As we mentioned in the last Newsletter, concepts that are important to our background knowledge include size anddistance (scale). It is important to put our Sun in the context of the other stars we see in the sky, so we willemphasize how big (mass and diameter) and bright (luminous) these stars are relative to our Sun. Also, because ofthe continuing discoveries of extrasolar planets, we will emphasize these concepts when we highlight theconstellations.

Hercules

The constellation of Hercules is somewhat faint although quite famous. It possesses 15 stars with a total of 17 known

exoplanets. yet only two stars brighter than third magnitude. The brightest star (Kornephoros or Beta Herculis) is aG-type (yellow, 4,900K) giant star that has used up the hydrogen in its core and is dying. With a mass is ~3 timesthat of the Sun and a diameter ~17 times that of the Sun, it is ~150 times more luminous than the Sun. The second-brightest star (Zeta Herculis) is a multiple star system with an F-type primary component (yellow-white, 5,800K;slightly hotter than the Sun) that is just starting to evolve off of the main sequence. The secondary star is a G-type(yellow, 5,300K) main sequence star very similar to our Sun. This star orbits the primary at about 15 AU (1.3 arcseconds as seen from the Earth) with an orbital period ~34.5 years. The star system is estimated to be about 6.2billion years old. The distances from Earth to Beta and Zeta Her are about 150 and 35 light-years, respectively.

Lyra

Lyra has only one star, Vega (Alpha Lyrae), brighter than third magnitude. However, Vega (Jody Foster’s star fromthe movie “Contact”) is perhaps the most influential star to astronomers because it not only defines the universalstandard for brightness but also was one of the first stars discovered with an orbiting ring of debris from whichplanets may be forming.

Vega is the fifth-brightest star in the night sky, an A-type (white, 9,600K) main sequence star about 455 millionyear-old. With a mass is about twice that of the Sun and a diameter ~2.6x that of the Sun, it is ~40 times moreluminous. However, there is a catch. From Earth we see Vega nearly pole-on. While the Sun rotates once in 25 to 34days (it rotates faster at the equator than at the poles), Vega rotates in just 12.5 hours (over 270 km/s at the equator)!If it rotated only 10% faster, its gravity would not be strong enough to keep it from flying apart. Because of this,Vega is “polar flattened” by 19%. Also, Vega is hotter at the poles (about 10,000K) than it is at the equator (about8,000K). You can read more about this phenomenon at:

http://www.space.com/1930-rapid-rotation-distorts-bright-star-vega.html

Aquila

Aquila has three stars brighter than third magnitude: Altair (Alpha Aquilae), Tarazed (Gamma Aquilae), and Denebel Okab (tail of the falcon; Zeta Aquilae). Altair is an A-type (white, average temperature 7,700K) main sequencestar. Its mass is 1.8 times that of the Sun and its diameter is 1.8 times larger. It is 11 times as luminous as the Sun.However, similar to Vega, it is rotating very rapidly, rotating once in 8.9 hours (a rotation velocity of 240 km/s at theequator). Because of this, the temperature ranges from 6,900K at the equator to 8,500K at the pole. Altair’sequatorial diameter is twice that of the Sun and its pole-to-pole diameter is only 1.6 times that of the Sun. Altair is amultiple-star system with three companions with magnitudes between 10 and 11.

Tarazed at magnitude 2.7 is a K-type (orange, 4,200K) giant star that has evolved off the main sequence even thoughit is estimated to be only 10 million years old. Its mass is ~6 times that of the Sun and its diameter is ~95 times thatof the Sun. It is about 2,500 times more luminous than the Sun. The distances to Altair and Tarazed are about 17 and460 light-years, respectively. Aquila has 10 stars with 12 known exoplanets.

Cygnus

The constellation Cygnus is the focus of NASA’s Kepler Mission which has detected many exoplanets in acontinuous search of 150,000 stars. Cygnus’ brightest star is Deneb (Alpha Cygni) with a magnitude of 1.25. Denebis an A-type (white, 8,500K) supergiant star that has already evolved off of the main sequence. It is thought that itwill go supernova within a few million years. Its mass is about 20 times that of the Sun and its diameter is about 200times that of the Sun. Its luminosity is estimated to be 200,000 times that of the Sun, making it one of the mostluminous stars known. The distance to Deneb has been estimated by several methods to be about 2,600 light-years,but one method places it at “only" 1,600 light-years away which would reduce its diameter to about 100 times that ofthe Sun and its luminosity to 60,000 times that of the Sun. There is a discussion of this at the Wikipedia site forDeneb. At the minimum estimated distance Deneb is the most distant of the 35 brightest stars that we can see. At itsmaximum estimated distance, it would be the most distant of the 100 brightest stars that we can see.

The fifth brightest star in Cygnus, Albireo (Beta Cygni). is a very famous binary star system, easily resolved in smalltelescopes as a colorful pair of stars. Alberio A is a K-type (orange, 4100 K) giant star with ~5x the mass of our Sunand 1000x the Sun’s luminosity. About 35 arcsec away is Albireo B, a B- type (blue-white, 12,000K) main sequencestar with a mass 3.7x that of the Sun and a luminosity about 200 times more. Based on the estimated distances, 400to 430 light-years from the Earth, it is thought that Albireo B is in a 100,000-year orbit around Albireo A. Albireo B

is a fast rotator, with a 15-hour period of rotation. However, in this case, this is fast enough for it to be losingmaterial to space so that it is surrounded by a disk of gas. Alberio A is itself a binary star that is only detectable fromits spectrum with two stars separated by the width of our Solar System (~40 AU).

Earth’s Pole stars

The Earth is like a top that wobbles (“precesses”) over a period of about 25,800 years. Because of this, over timedifferent stars are aligned in the direction of Earth’s rotation axis. At the present time, Polaris in Ursa Minor is ourpole star. At the moment, Polaris is 0.7 degrees (1.4 times the diameter of the Moon) away from Earth’s axis ofrotation and will be closest around 2100 AD. Around 2800 BC Thuban, the heart of Draco the Dragon, was the polestar. If we wait around, Deneb will be within 5 degrees of the pole around 10000 AD and Vega will be the pole star(within about 4 degrees) around 14000 AD.

Clear Skies and Good Observing!

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Alachua Astronomy Club, Inc.P.O. Box 141591Gainesville, FL 32614-1591

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