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The Prairie AstronomerDecember 2015 Volume 56, Issue #12
MSRAL
The Newsletter of the Prairie Astronomy Club
The MountainousShoreline of SputnikPlanum
DecemberProgram
Mark Dahmke:Adventures in
Astrophotography
The Prairie Astronomer
NEXT PAC MEETING: December 29, 6:30pmHoliday Gathering at Mueller PlanetariumPROGRAM“Adventures in Astrophotography” by MarkDahmke. Google Earth and other software toolsand websites make it relatively easy to plan andexecute photo shoots of terrestrial subjects withthe Moon or other celestial objects. Mark will showhow to go find targets of opportunity and will alsooffer some tips on equipment and proper exposureto help you shoot great astro photos.
We will have refreshments, popcorn, cookies,cake.
CONTENTS
4 Meeting Minutes
6 Titan’s Haze
8 Astrophotos
9 Gyulbudaghian'sNebula
11 Ceres’ Bright Spots
14 Occator
15 Venus Climate Orbiter
16 January Observing
17 Focus onConstellations
18 Imaging a EventHorizon
20 Pluto’s Pits
21 From the Archives
22 Triple Crescents
23 Earthrise
24 Mars Silica Rocks
26 Club InformationBuy the book! The PrairieAstronomy Club: Fifty Yearsof Amateur Astronomy.Order online from Amazon orlulu.com.
FUTURE PROGRAMS
January: “How to Use Your Telescope”
The Prairie Astronomer 3
PAC E-MAIL:[email protected]
PAC-LIST:Subscribe through GoogleGroups.To post messages to the list, sendto the address:[email protected]
Dates in underlined are closest to the new moon
Jan 16,23, Feb 13,20Mar 13,20, Apr 10,17May 8,15, Jun 12,19Jul 10,17NSP Jul 12-17Aug 7,14, Sep 4,11Oct 9,16, Nov 6,13Dec 4,11
Lunar Party DatesMar 27, Apr 24, Jul 24, Aug 21
(Lunar party dates are tentative, sites to be determined.)
PAC Star Party Dates
The Prairie Astronomerc/o The Prairie Astronomy Club, Inc.P.O. Box 5585Lincoln, NE 68505-0585
ADDRESS
EVENTS
Photo by Brian Sivill
2015 STAR PARTY DATES
WEBSITESwww.prairieastronomyclub.orghttps://nightsky.jpl.nasa.govwww.hydeobservatory.infowww.nebraskastarparty.orgwww.OmahaAstro.comPanhandleastronomyclub.comwww.universetoday.com/www.planetary.org/home/http://www.darksky.org/
PAC Holiday Gathering (members only)Tuesday December 29th, 2015, 6:30pmMueller Planetarium
Newsletter submission deadline January 16
PAC Meeting“How to Use Your Telescope”Tuesday January 26th, 2016, 7:30pmHyde Observatory
PAC MeetingTuesday February 23rd, 2016, 7:30pmHyde Observatory
The Prairie Astronomer 4
Minutes for the meeting ofNovember 24, 2015President Jim Kvasnicka calledthe meeting to order. 15members, 2 guests: Dan,Denira(?)Upcoming events:Hyde is open every Saturday7-10 PMThe next star parties are Dec 4& 11 at the farm.The December PAC meeting willbe Dec 29, our holidaygathering. We are discussing
having this at MuellerPlanetarium.Jim reviewed dues and benefitsof club membership.Jim provided the Decemberobserving report, with a focus onthe constellation Perseus.Club business:Jim introduced our current clubofficers:President and observing chair,Jim KvasnickaVice President, Brett Boller
2nd VP (Program chair) BethJenckesSecretary, Lee TaylorTreasurer, John ReinertNewsletter editor, Mark Dahmkeeclipse coordinator (newposition) Dave ChurillaAdjourn to program, How to Buya Telescope.Respectfully submitted by,Lee Taylor
PAC Meeting Minutes
Prairie Astronomy Club
Minutes for the Board ofDirectors meeting Oct. 29, 2015
Members present:
Jim Kvasnicka, PresidentBrett Boller, Vice PresidentJohn Reinert, TreasurerLee Taylor, Secretary
Others present:
Dan Delzell, Outreachcoordinator
November meeting:
Our November meeting will be'How to buy a telescope'. Our
idea this year is to have stationswith the different designs oftelescopes available, a stationon accessories, and examples ofwhat to avoid. We'll have arefractor, reflector, and an SCTfor people to look over and try.We would also like to have thetelescope on Hyde's deckavailable. We will have a shortpresentation to start things off.
We will try to get publicity forthis, using the usual outlets.
December gathering
Jim will try to contact Zach for aholiday gathering at Mueller.Larry Stepp will NOT beavailable, but others may haveother things to present. We will
have snacks available, likelast year.
Club equipment
The club 13-inch has beenchecked out by Rick Brown.However, there is nosecondary. We will do whatwe can to get that fixed. The100mm refractor is on Hyde'sdeck, available for checkout,as are the 10-inch and thenew dob without a base. Wediscussed ways to get thebase for this.
PAC Board Meeting Minutes
The Prairie Astronomer 5
Star PartyDate
Star PartyDate Lunar Party Date
January Jan 1st Jan 8thFebruary Jan 29th Feb 5thMarch Mar 4th Mar 11thApril Apr 1st Apr 8th Apr 15thMay Apr 29th May 6th May 13thJune May 27th Jun 3rdJuly Jul 1st Jul 8th
NSP July 31st -August 5th
August Jul 29th Aug 5th Aug 12thAugust Aug 26th Sep 2nd Sep 9thSeptember Sep 23rd Sep 30thOctober Oct 21st Oct 28thNovember Nov 25th Dec 2ndDecember Dec 23rd Dec 30th
2016 Star Party Dates
xkcd.com
The Prairie Astronomer 6
Peering Through Titan’s Haze
The Prairie Astronomer 7
This view from NASA's Cassinispacecraft, acquired during themission's 'T-114' flyby on Nov.13, 2015, looks toward terrainthat is mostly on the Saturn-facing hemisphere of Titan.
This composite image shows aninfrared view of Saturn's moonTitan from NASA's Cassinispacecraft, acquired during themission's "T-114" flyby on Nov.13, 2015. The spacecraft'svisual and infrared mappingspectrometer (VIMS) instrumentmade these observations, inwhich blue representswavelengths centered at 1.3microns, green represents 2.0microns, and red represents 5.0microns. A view at visiblewavelengths (centered around0.5 microns) would show onlyTitan's hazy atmosphere (as inPIA14909). The near-infraredwavelengths in this image allowCassini's vision to penetrate thehaze and reveal the moon'ssurface.
During this Titan flyby, thespacecraft's closest-approachaltitude was 6,200 miles (10,000kilometers), which isconsiderably higher than thoseof typical flybys, which arearound 750 miles (1,200kilometers). The high flybyallowed VIMS to gathermoderate-resolution views overwide areas (typically at a fewkilometers per pixel).
The view looks toward terrainthat is mostly on the Saturn-facing hemisphere of Titan. Thescene features the parallel, dark,
dune-filled regions namedFensal (to the north) and Aztlan(to the south), which form theshape of a sideways letter "H."
Several places on the imageshow the surface at higherresolution than elsewhere.These areas, called subframes,show more detail because theywere acquired near closestapproach. They have finerresolution, but cover smallerareas than data obtained whenCassini was farther away fromTitan.
Near the limb at left, abovecenter, is the best VIMS view sofar of Titan's largest confirmedimpact crater, Menrva (first seenby the RADAR instrument inPIA07365). Similarly detailedsubframes show easternXanadu, the basin Hotei Regio,and channels within brightterrains east of Xanadu. (ForTitan maps with named featuresseehttp://planetarynames.wr.usgs.gov/Page/TITAN/target.)
Due to the changing Saturnianseasons, in this late northernspring view, the illumination issignificantly changed from thatseen by VIMS during the "T-9"flyby on December 26, 2005(PIA02145). The sun has movedhigher in the sky in Titan'snorthern hemisphere, and lowerin the sky in the south, asnorthern summer approaches.This change in the sun's anglewith respect to Titan's surfacehas made high southernlatitudes appear darker, while
northern latitudes appearbrighter.
The Cassini mission is acooperative project of NASA,ESA (the European SpaceAgency) and the Italian SpaceAgency. The Jet PropulsionLaboratory, a division of theCalifornia Institute ofTechnology in Pasadena,manages the mission forNASA's Science MissionDirectorate, Washington. TheCassini orbiter and its twoonboard cameras weredesigned, developed andassembled at JPL. The visualand infrared mappingspectrometer team is based atthe University of Arizona.
For more information about theCassini-Huygens missionhttp://saturn.jpl.nasa.gov/home/index.cfm. The visual andinfrared mapping spectrometerteam homepage is athttp://www.vims.lpl.arizona.edu.
Peering Through Titan’s Haze
The Prairie Astronomer 8
AstrophotographyPhotos by Beth Jenckes. Canon EOS REBEL T2i,, ISO 800, f/5.6, 30 seconds
Orion at SunsetTaurus and Pleiades
Orion and TaurusPleiades
The Moon by Mark Dahmke.
Panasonic Lumix DMC-G7 capturing video at 4K(3840x2160) resolution, ISO6400, 30fps. Thevideo was then split into 16-bit TIFs. 60 of theframes were stacked using Registax.
Celstron Onyx 80EDF 80mm refractor at primefocus.
The Prairie Astronomer 9
I've always updated my image ofGyulbudaghian's Nebula, avariable nebula, about once ayear. I took this year's versionin July earlier than usual hopingto try again in a few months. Itdidn't get processed until earlierthis month (See update #15-156for 11-04-15) which remindedme I was going to try again.Unfortunately conditions so farthis month have been very bad.Fog and haze moved in even asthe first frame was starting. Iended up taking 8 luminanceframes none of which were verygood but combining all 8 I sort of
got something useful. Therewere nasty fog halos aroundbright stars I sort of dealt with.Removing them but not thenebula behind them was quite achallenge. Color data was verypoor due to the fog. I aboutgave up on processing this butfinally managed to getsomething useful by using thecolor data from last July so if itchanged color this image won'tshow that. I could try againonce the moon is out of theway. If so that would give a veryshort term view of how itchanges. Looking at the
November 8image it looksmuch like itdid a year agorather than asit did in July.So it may verywell showvariations inonly two or three weeks time. Ifthe weather ever cooperatesmaybe I can find out. But it'sbiggest change appears to be inPV Cephei itself. Being aprotostar it is an irregularvariable commonly runningabout magnitude 16.5 but with
Gyulbudaghian's NebulaRick Johnson
The Prairie Astronomer 10
sudden peaks to 15 and slowdips to 18th magnitude. Exceptfor this image all the othersappear rather constant at mid16th magnitude. Due to it beingembedded in nebulosity I can't
get a good measurement but itappears about 14.8 in myimages which would put it near atypical maximum. Somethingnone of my other images havecaught before.
For more on this nebula see myNovember 4th post.
The Prairie Astronomer 11
New Clues to Ceres' Bright Spots and Origins
Ceres reveals some of its well-kept secrets in two new studiesin the journal Nature, thanks todata from NASA's Dawnspacecraft. They include highlyanticipated insights aboutmysterious bright features foundall over the dwarf planet'ssurface.
In one study, scientists identifythis bright material as a kind ofsalt. The second study suggeststhe detection of ammonia-richclays, raising questions abouthow Ceres formed.
About the Bright Spots
Ceres has more than 130 brightareas, and most of them areassociated with impact craters.Study authors, led by AndreasNathues at Max Planck Institutefor Solar System Research,Göttingen, Germany, write thatthe bright material is consistentwith a type of magnesiumsulfate called hexahydrite. Adifferent type of magnesiumsulfate is familiar on Earth asEpsom salt.
Nathues and colleagues, usingimages from Dawn's framingcamera, suggest that these salt-rich areas were left behind whenwater-ice sublimated in the past.Impacts from asteroids wouldhave unearthed the mixture ofice and salt, they say.
"The global nature of Ceres'bright spots suggests that thisworld has a subsurface layer
that contains briny water-ice,"Nathues said.
A New Look at Occator
The surface of Ceres, whoseaverage diameter is 584 miles(940 kilometers), is generallydark -- similar in brightness tofresh asphalt -- study authorswrote. The bright patches thatpepper the surface represent alarge range of brightness, withthe brightest areas reflectingabout 50 percent of sunlightshining on the area. But therehas not been unambiguousdetection of water ice on Ceres;higher-resolution data areneeded to settle this question.
The inner portion of a cratercalled Occator contains thebrightest material on Ceres.Occator itself is 60 miles (90kilometers) in diameter, and itscentral pit, covered by this brightmaterial, measures about 6miles (10 kilometers) wide and0.3 miles (0.5 kilometers) deep.Dark streaks, possibly fractures,traverse the pit. Remnants of acentral peak, which was up to0.3 miles (0.5 kilometers) high,can also be seen.
With its sharp rim and walls, andabundant terraces and landslidedeposits, Occator appears to beamong the youngest features onCeres. Dawn mission scientistsestimate its age to be about 78million years old.
Study authors write that someviews of Occator appear to show
a diffuse haze near the surfacethat fills the floor of the crater.This may be associated withobservations of water vapor atCeres by the Herschel spaceobservatory that were reportedin 2014. The haze seems to bepresent in views during noon,local time, and absent at dawnand dusk, study authors write.This suggests that thephenomenon resembles theactivity at the surface of acomet, with water vapor liftingtiny particles of dust andresidual ice. Future data andanalysis may test thishypothesis and reveal cluesabout the process causing thisactivity.
"The Dawn science team is stilldiscussing these results andanalyzing data to betterunderstand what is happening atOccator," said Chris Russell,principal investigator of theDawn mission, based at theUniversity of California, LosAngeles.
The Importance of Ammonia
In the second Nature study,members of the Dawn scienceteam examined the compositionof Ceres and found evidence forammonia-rich clays. They useddata from the visible andinfrared mapping spectrometer,a device that looks at howvarious wavelengths of light arereflected by the surface,allowing minerals to beidentified.
The Prairie Astronomer 12
Ammonia ice by itself wouldevaporate on Ceres today,because the dwarf planet is toowarm. However, ammoniamolecules could be stable ifpresent in combination with (i.e.chemically bonded to) otherminerals.
The presence of ammoniatedcompounds raises the possibilitythat Ceres did not originate inthe main asteroid belt betweenMars and Jupiter, where itcurrently resides, but insteadmight have formed in the outersolar system. Another idea isthat Ceres formed close to itspresent position, incorporatingmaterials that drifted in from theouter solar system - near theorbit of Neptune, where nitrogenices are thermally stable.
"The presence of ammonia-bearing species suggests thatCeres is composed of materialaccreted in an environmentwhere ammonia and nitrogenwere abundant. Consequently,we think that this materialoriginated in the outer cold solarsystem," said Maria Cristina DeSanctis, lead author of thestudy, based at the NationalInstitute of Astrophysics, Rome.
In comparing the spectrum ofreflected light from Ceres tometeorites, scientists foundsome similarities. Specifically,they focused on the spectra, orchemical fingerprints, ofcarbonaceous chondrites, a typeof carbon-rich meteorite thoughtto be relevant analogues for thedwarf planet. But these are notgood matches for allwavelengths that the instrumentsampled, the team found. Inparticular, there were distinctive
absorption bands, matchingmixtures containing ammoniatedminerals, associated withwavelengths that can't beobserved from Earth-basedtelescopes.
The scientists note anotherdifference is that thesecarbonaceous chondrites havebulk water contents of 15 to 20percent, while Ceres' content isas much as 30 percent.
"Ceres may have retained morevolatiles than these meteorites,or it could have accreted thewater from volatile-richmaterial," De Sanctis said.
The study also shows thatdaytime surface temperatureson Ceres span from minus 136degrees to minus 28 degreesFahrenheit (180 to 240 Kelvin).The maximum temperatureswere measured in the equatorialregion. The temperatures at andnear the equator are generallytoo high to support ice at thesurface for a long time, studyauthors say, but data fromDawn's next orbit will revealmore details.
As of this week, Dawn hasreached its final orbital altitudeat Ceres, about 240 miles (385kilometers) from the surface ofthe dwarf planet. In mid-December, Dawn will begintaking observations from thisorbit, including images at aresolution of 120 feet (35meters) per pixel, infrared,gamma ray and neutron spectra,and high-resolution gravity data.
Dawn's mission is managed bythe Jet Propulsion Laboratory forNASA. Dawn is a project of the
directorate's Discovery Program,managed by NASA's MarshallSpace Flight Center inHuntsville, Alabama. UCLA isresponsible for overall Dawnmission science. Orbital ATKInc., in Dulles, Virginia, designedand built the spacecraft. TheGerman Aerospace Center, MaxPlanck Institute for Solar SystemResearch, Italian Space Agencyand Italian NationalAstrophysical Institute areinternational partners on themission team.
The Prairie Astronomer 13
An image of Occator Crater draped over a digital terrain model provides a 3-D-like perspective viewof the impact structure. Several bright areas can be seen in this crater. The inner part of the craterforms a type of "crater within a crater" measuring about 6 miles (10 kilometers) in diameter and 0.3miles (0.5 miles) in depth, and contains the brightest material on all of Ceres. Occator measuresabout 60 miles (90 kilometers) wide.
With its sharp rim and walls, and abundant terraces and landslide deposits, Occator appears to beamong the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78million years old.
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn isa project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Centerin Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., inDulles, Virginia, designed and built the spacecraft. The German Aerospace Center, the Max PlanckInstitute for Solar System Research, the Italian Space Agency and the Italian National AstrophysicalInstitute are international partners on the mission team. For a complete list of acknowledgments,see http://dawn.jpl.nasa.gov/mission.
For more information about the Dawn mission, visit http://dawn.jpl.nasa.gov.
Occator Crater
The Prairie Astronomer 14
A group of scientists from NASA's Dawn mission suggests that when sunlight reaches Ceres' OccatorCrater, a kind of thin haze of dust and evaporating water forms there. This haze only becomes denseenough to be seen by looking at it laterally, as in this image, the scientists wrote in the journal Naturein December 2015.
Occator measures about 60 miles (90 kilometers) wide, and contains the brightest material seen onCeres.
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn isa project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Centerin Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., inDulles, Virginia, designed and built the spacecraft. The German Aerospace Center, the Max PlanckInstitute for Solar System Research, the Italian Space Agency and the Italian National AstrophysicalInstitute are international partners on the mission team. For a complete list of acknowledgments, seehttp://dawn.jpl.nasa.gov/mission.
Lateral View of Occator
The Prairie Astronomer 15
The Japan AerospaceExploration Agency (JAXA)successfully inserted the VenusClimate Orbiter “AKATSUKI” intothe orbit circling around Venus.
As a result of measuring andcalculating the AKATSUKI’s orbitafter its thrust ejection, theorbiter is now flying on theelliptical orbit at the apoapsisaltitude of about 400 km andperiapsis altitude of about440,000 km from Venus. Theorbit period is 13 days and 14hours. We also found that theorbiter is flying in the samedirection as that of Venus’srotation.
The AKATSUKI is in goodhealth.
We will deploy the threescientific mission instrumentsnamely the 2μm camera (IR2),the Lightning and AirglowCamera (LAC) and the Ultra-Stable oscillator (USO) andcheck their functions. JAXA willthen perform initialobservations withthe above threeinstruments alongwith the three otherinstruments whosefunction hasalready beenconfirmed, theUltraviolet Imager(UVI), theLongwave IRcamera (LIR), andthe 1μm camera(IR1) for aboutthree months. Atthe same time,
JAXA will also graduallyadjust the orbit for shifting itselliptical orbit to the period ofabout nine days. The regularoperation is scheduled tostart in April, 2016.
Venus Climate Orbiter “AKATSUKI” Inserted Into Venus' Orbit
The Prairie Astronomer 16
This is a partial list of objects visible for theupcoming month.
Planets
Neptune and Uranus: In Aquarius and Pisces.Mercury: Shines at -0.4 magnitude on January1st 10° above the SW horizon. It quickly dims to1.8 magnitude and reaches inferior conjunctionon January 14th.Jupiter: Rises around 10:30 pm to start themonth and by 8:30 at the end.Mars: Rises around 1:30 am to start the month inVirgo.Venus: Rises 3 hours before the Sun to startJanuary and 2 hours at the end of the month.Saturn: On January 9th Saturn is just ½° to theupper right of Venus. Soon after this conjunctionSaturn opens a wide gap with Venus. OnJanuary 24th it passes close to M20 the TrifidNebula in Sagittarius.
Meteor Showers
Quadrantids: Peaks on January 4th at 2:00 amCentral Time. The moon will be a waningcrescent rising about an hour after the peak.Peak rates have varied from 60-200.
Messier List
M33: The Triangulum Galaxy.M34: Open cluster in Perseus.M52: Open cluster in Cassiopeia.M74: Galaxy in Pisces.M76: The Little Dumbbell in Perseus.M77: Galaxy in Cetus.M103: Open cluster in Cassiopeia.Last Month: M2, M15, M29, M31, M32, M110Next Month: M35, M36, M37, M38, M42, M43,M45, M78, M79
NGC and other Deep SkyObjects
Collinder 69: Opencluster in Orion.NGC 1980: Emissionnebula and open cluster inOrion.NGC 2169: The 37 Clusterin Orion.
Double Star Program List
Beta Orionis: Rigel, white and dim blue stars.Delta Orionis: Mintaka, Bright white and paleblue pair.Struve 747: Equal pair of white stars in Orion.Lambda Orionis: Pair of white stars.Theta 1 Orionis: The Trapezium in the OrionNebula.Iota Orionis: White and blue stars.Theta 2 Orionis: Three white stars.Sigma Orionis: White star with 3 pale blue stars.Zeta Orionis: Alnitak, white star with two whitesecondary stars.
Challenge Object
B33: The Horsehead Nebula. A dark nebulasilhouetted against IC 434 in Orion.
January Observing: What to ViewJim Kvasnicka
The Prairie Astronomer 17
OrionOrion the Hunter is perhaps second only to theBig Dipper in Ursa Major as the mostrecognizable star pattern in the sky. It covers1,231 square degrees. Orion is accompanied byhis faithful dogs, Canis Major and Canis Minor.Together they hunt various celestial animalsincluding Lepus the rabbit and Taurus, the Bull.The three bright stars Alnitak, Alnilam, andMintaka make up Orion’s belt. Betelgeuse formsOrion’s left shoulder. Hanging down from Orion’sbelt is his sword. The central star of his sword isnot really a star, but the Great Orion Nebula,M42, one of the most famous and observedobjects in the sky. Besides M42 Orion has twoadditional Messier objects in bright nebulae M43and M78. The constellation Orion is bestobserved in January.
Showpiece ObjectsOpen Clusters: NGC 1981, NGC 2169 (The 37Cluster)Bright Nebulae: M42 (The Orion Nebula), M43,M78, NGC 1977, NGC 1980Multiple Stars: Beta Orionis (Rigel), DeltaOrionis (Mintaka), Theta 1 Orionis (TheTrapezium), Sigma OrionisDark Nebulae: B33 (The Horsehead Nebula)
MythologyOrion, the son of Neptune, boasted that so greatwas his might and skill as a hunter that he couldkill all the animals on Earth. Gaea, Goddess ofEarth, was alarmed by such a boastful statement.Gaea was afraid that Orion might try to carry out
his boast. Gaea sent a giant scorpion andordered the beast to sting Orion. After a briefbattle the scorpion stung Orion in the heel (thestar Rigel) and he died. Both Orion and thescorpion were given honored places in the sky,but they were placed at opposite ends of the skydome so they would never engage in battle again.
Number of Objects Magnitude 12.0 andBrighterGalaxies: 0Open Clusters: 11Planetary Nebulae: 0Bright Nebulae: 9Dark Nebulae: 6
Focus on Constellations: OrionJim Kvasnicka
"Orion 3008 huge" by Mouser - Own work.Licensed under CC BY-SA 3.0 via Commons -
The Prairie Astronomer 18
How Will We Finally Image the Event Horizon of a Black Hole?
Ethan Siegel
One hundred years ago, AlbertEinstein first put forth his theoryof General Relativity, which laidout the relationship betweenspacetime and the matter andenergy present within it. While itsuccessfully recoveredNewtonian gravity andpredicted the additionalprecession of Mercury's orbit,the only exact solution thatEinstein himself discovered wasthe trivial one: that forcompletely empty space. Lessthan two months after releasinghis theory, however, theGerman scientist KarlSchwarzschild provided a trueexact solution, that of amassive, infinitely dense object,a black hole.
One of the curious things thatpopped out of Schwarzschild'ssolution was the existence of anevent horizon, or a region ofspace that was so severelycurved that nothing, not evenlight, could escape from it. Thesize of this event horizon wouldbe directly proportional to themass of the black hole. A blackhole the mass of Earth wouldhave an event horizon less thana centimeter in radius; a blackhole the mass of the sun wouldhave an event horizon just a
few kilometers in radius; and asupermassive black hole wouldhave an event horizon the sizeof a planetary orbit.
Our galaxy has since beendiscovered to house a blackhole about four million solarmasses in size, with an eventhorizon about 23.6 millionkilometers across, or about 40percent the size of Mercury'sorbit around the sun. At adistance of 26,000 light years,it's the largest event horizon inangular size visible from Earth,but at just 19 micro-arc-seconds, it would take atelescope the size of Earth toresolve it – a practicalimpossibility.
But all hope isn't lost! If insteadof a single telescope, we builtan array of telescopes locatedall over Earth, we couldsimultaneously image thegalactic center, and use thetechnique of VLBI (very long-baseline interferometry) toresolve the black hole's eventhorizon. The array would onlyhave the light-gathering powerof the individual telescopes,meaning the black hole (in theradio) will appear very faint, butthey can obtain the resolution of
a telescope that's the distancebetween the farthest telescopesin the array! The planned EventHorizon Telescope, spanningfour different continents(including Antarctica), shouldbe able to resolve under 10micro-arc-seconds, imaging ablack hole directly for the firsttime and answering thequestion of whether or not theytruly contain an event horizon.What began as a meremathematical solution is nowjust a few years away frombeing observed and known forcertain!
This article is provided by NASA Space Place.With articles, activities, crafts, games, and lesson plans, NASA SpacePlace encourages everyone to get excited about science and technology.Visit spaceplace.nasa.gov to explore space and Earth science!
Note: This month’s article describes a project that is not related to NASA and does not suggest any relationship orendorsement. Its coverage is for general interest and educational purposes.
The Prairie Astronomer 19
Image credit: NASA/CXC/Amherst College/D.Haggard et al., of the galactic center in X-rays.Sagittarius A* is the supermassive black hole at our Milky Way's center, which normally emits X-raylight of a particular brightness. However, 2013 saw a flare increase its luminosity by a factor of manyhundreds, as the black hole devoured matter. The event horizon has yet to be revealed.
Galactic Center in X-rays
The Prairie Astronomer 20
On July 14 the telescopiccamera on NASA’s NewHorizons spacecraft took thehighest resolution images everobtained of the intricate patternof “pits” across a section ofPluto’s prominent heart-shapedregion, informally namedTombaugh Regio. Missionscientists believe thesemysterious indentations mayform through a combination ofice fracturing and evaporation.The scarcity of overlying impactcraters in this area also leadsscientists to conclude that thesepits – typically hundreds ofyards across and tens of yardsdeep – formed relativelyrecently. Their alignment
provides clues about the iceflow and the exchange ofnitrogen and other volatilematerials between the surfaceand the atmosphere.
The image is part of a sequencetaken by New Horizons’ LongRange Reconnaissance Imager(LORRI) as the spacecraftpassed within 9,550 miles(15,400 kilometers) of Pluto’ssurface, just 13 minutes beforethe time of closest approach.The small box on the globalview shows the section of theregion imaged in the southeastcorner of the giant ice sheetinformally named SputnikPlanum. The magnified view is
50-by-50 miles (80-by-80kilometers) across. The largering-like structure near thebottom right of the magnifiedview -- and the smaller onenear the bottom left -- may beremnant craters. The upper-left quadrant of the imageshows the border betweenthe relatively smooth SputnikPlanum ice sheet and thepitted area, with a series ofhills forming slightly insidethis unusual “shoreline.”
Credit: NASA/JHUAPL/SwRI
Zooming in on Pluto’s Pattern of Pits
The Prairie Astronomer 21
From the Archives: December, 1966
The President’s Report
December, 1966
A grazing occultation occurred on Dec 18th at 6:45pm local time. This was one of the best plannedand attended occultations observed that our club has participated in. About ten or so membersgathered at my place on the afternoon of the event. After locating our viewing spot on the survey mapwe had lunch and then departed for the site about 24 miles south of Firth. We had all the equipmentnecessary. Rick Johnson brought his new 10 inch f/8, a tape record and shortwave radio to pick uptime signals and I had my 8in and the 2.4in refractor. But the best laid plans of mice and men, etc.Wouldn’t you know after a week of clear warm dry weather that those clouds would have to move in.We could see the Moon through the clouds but not the star, not even in the 10 inch.
Well, we plan another one on Dec 31st at 3 am. This will be a third mag that failed to show throughthe clouds on Dec. 18. This graze will be a little closer to home. About one half mile south of myplace. I will be out there. Hope to see some of you there also.
–Earl Moser, President.
* * * * * *
Our next meeting will be Dec 27th, Tuesday night, 7:30pm at the Nebr. Wesleyan Science Building.
The program will be a good one. Monte Cole will give a report on Astronomical Facts, from a 1919Copyrighted Encyclopedia. A film if possible. We are going to sell those lenses that Felix Cavosiegave to the club. There’s a lot of them so come prepared to take some of them home. The sellingprice will be low, and the money will go into our treasury.
Have a good Christmas and I hope everyone finds two or more Good Eyepieces, or whatever youbeen needin, in your sock.
A group of us got together a week or so ago, and demonstrated our scopes to some of Prof. CarrollMoore’ students. It was very nice of you boys to turn out. Next year we should do it earlier in themonth, or sooner still, so that anyone wishing to order a telescope would get ahead of the Christmasrush.
So, meeting Dec 27. You know where and the time. Refreshments. –Happy Holidays, Jess Williams.
The Prairie Astronomer 22
A single crescent moon is a familiar sight in Earth's sky, but with Saturn's many moons, you can seethree or even more.
The three moons shown here -- Titan (3,200 miles or 5,150 kilometers across), Mimas (246 miles or396 kilometers across), and Rhea (949 miles or 1,527 kilometers across) -- show marked contrasts.Titan, the largest moon in this image, appears fuzzy because we only see its cloud layers. Andbecause Titan's atmosphere refracts light around the moon, its crescent "wraps" just a little furtheraround the moon than it would on an airless body. Rhea (upper left) appears rough because its icysurface is heavily cratered. And a close inspection of Mimas (center bottom), though difficult to see atthis scale, shows surface irregularities due to its own violent history.
This view looks toward the anti-Saturn hemisphere of Titan. North on Titan is to the right. The imagewas taken in visible light with the Cassini spacecraft narrow-angle camera on March 25, 2015.
The view was obtained at a distance of approximately 2.7 million miles (4.3 million kilometers) fromTitan. Image scale at Titan is 16 miles (26 kilometers) per pixel. Mimas was 1.9 million miles (3.0million kilometers) away with an image scale of 11 miles (18 kilometers) per pixel. Rhea was 1.6million miles (2.6 million kilometers) away with an image scale of 9.8 miles (15.7 kilometer) per pixel.
The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and theItalian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute ofTechnology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.The imaging operations center is based at the Space Science Institute in Boulder, Colorado.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov andhttp://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org.
Triple Crescents
The Prairie Astronomer 23
NASA's Lunar Reconnaissance Orbiter (LRO) recently captured a unique view of Earth from thespacecraft's vantage point in orbit around the moon.
"The image is simply stunning," said Noah Petro, Deputy Project Scientist for LRO at NASA'sGoddard Space Flight Center in Greenbelt, Maryland. "The image of the Earth evokes the famous'Blue Marble' image taken by Astronaut Harrison Schmitt during Apollo 17, 43 years ago, which alsoshowed Africa prominently in the picture."
In this composite image we see Earth appear to rise over the lunar horizon from the viewpoint of thespacecraft, with the center of the Earth just off the coast of Liberia (at 4.04 degrees North, 12.44degrees West). The large tan area in the upper right is the Sahara Desert, and just beyond is SaudiArabia. The Atlantic and Pacific coasts of South America are visible to the left. On the moon, we get aglimpse of the crater Compton, which is located just beyond the eastern limb of the moon, on thelunar farside.
“Blue Marble”
The Prairie Astronomer 24
Rocks Rich in Silica Present Puzzles for Mars Rover Team
In detective stories, as the plotthickens, an unexpected clueoften delivers more questionsthan answers. In this case, thescene is a mountain on Mars.The clue: the chemicalcompound silica. Lots of silica.The sleuths: a savvy band ofEarthbound researchers whoseagent on Mars is NASA's laser-flashing, one-armed mobilelaboratory, Curiosity.
NASA's Curiosity rover hasfound much higherconcentrations of silica at somesites it has investigated in thepast seven months thananywhere else it has visitedsince landing on Mars 40months ago. Silica makes upnine-tenths of the composition ofsome of the rocks. It is a rock-forming chemical combining theelements silicon and oxygen,commonly seen on Earth as
quartz, but also in many otherminerals.
"These high-silica compositionsare a puzzle. You can boost theconcentration of silica either byleaching away other ingredientswhile leaving the silica behind,or by bringing in silica fromsomewhere else," said AlbertYen, a Curiosity science teammember at NASA's JetPropulsion Laboratory,Pasadena, California. "Either ofthose processes involve water. Ifwe can determine whichhappened, we'll learn moreabout other conditions in thoseancient wet environments."
Water that is acidic would tendto carry other ingredients awayand leave silica behind. Alkalineor neutral water could bring indissolved silica that would bedeposited from the solution.
Apart from presenting apuzzle about the history of theregion where Curiosity isworking, the recent findingson Mount Sharp haveintriguing threads linked towhat an earlier NASA rover,Spirit, found halfway aroundMars. There, signs of sulfuricacidity were observed, butCuriosity's science team isstill considering bothscenarios -- and others -- toexplain the findings on MountSharp.
Adding to the puzzle, somesilica at one rock Curiositydrilled, called "Buckskin," is ina mineral named tridymite,rare on Earth and never seenbefore on Mars. The usualorigin of tridymite on Earthinvolves high temperatures inigneous or metamorphicrocks, but the finely layered
This May 22, 2015, view from the Mast Camera (Mastcam) in NASA's Curiosity Mars rover shows the"Marias Pass" area where a lower and older geological unit of mudstone -- the pale zone in the centerof the image -- lies in contact with an overlying geological unit of sandstone. Credit: NASA/JPL-Caltech/MSSS
The Prairie Astronomer 25
sedimentary rocks examined byCuriosity have been interpretedas lakebed deposits.Furthermore, tridymite is foundin volcanic deposits with highsilica content. Rocks on Mars'surface generally have lesssilica, like basalts in Hawaii,though some silica-rich (silicic)rocks have been found by Marsrovers and orbiters. Magma, themolten source material ofvolcanoes, can evolve on Earthto become silicic. Tridymitefound at Buckskin may beevidence for magmaticevolution on Mars.
Curiosity has been studyinggeological layers of MountSharp, going uphill, since 2014,after two years of productivework on the plains surroundingthe mountain. The missiondelivered evidence in its firstyear that lakes in the areabillions of years ago offeredfavorable conditions for life, ifmicrobes ever lived on Mars. AsCuriosity reaches successivelyyounger layers up MountSharp's slopes, the mission isinvestigating how ancientenvironmental conditionsevolved from lakes, rivers anddeltas to the harsh aridity oftoday's Mars.
Seven months ago, Curiosityapproached "Marias Pass,"where two geological layers areexposed in contact with eachother. The rover's laser-firinginstrument for examiningcompositions from a distance,Chemistry and Camera(ChemCam), detected bountifulsilica in some targets the roverpassed on its way to the contact
zone. The rover's DynamicAlbedo of Neutrons instrumentsimultaneously detected thatthe rock composition wasunique in this area.
"The high silica was a surprise-- so interesting that webacktracked to investigate itwith more of Curiosity'sinstruments," said JensFrydenvang of Los AlamosNational Laboratory in NewMexico and the University ofCopenhagen, Denmark.
Gathering clues about silicawas a major emphasis in roveroperations over a span of fourmonths and a distance of aboutone-third of a mile (half akilometer).
The investigations includedmany more readings fromChemCam, plus elementalcomposition measurements bythe Alpha Particle X-raySpectrometer (APXS) on therover's arm and mineralidentification of rock-powdersamples by the Chemistry andMineralogy (CheMin) instrumentinside the rover.
Buckskin was the first of threerocks where drilled sampleswere collected during thatperiod. The CheMinidentification of tridymiteprompted the team to look atpossible explanations: "Wecould solve this by determiningwhether trydymite in thesediment comes from a volcanicsource or has another origin,"said Liz Rampe, of AerodyneIndustries at NASA's JohnsonSpace Center, Houston. "A lotof us are in our labs trying to
see if there's a way to maketridymite without such a hightemperature."
Beyond Marias Pass,ChemCam and APXS founda pattern of high silica in palezones along fractures in thebedrock, linking the silicaenrichment there to alterationby fluids that flowed throughthe fractures and permeatedinto bedrock. CheMinanalyzed drilled material froma target called "Big Sky" inbedrock away from a fractureand from a fracture-zonetarget called "Greenhorn."Greenhorn indeed has muchmore silica, but not any in theform of tridymite. Much of it isin the form of noncrystallineopal, which can form in manytypes of environments,including soils, sediments,hot spring deposits and acid-leached rocks.
"What we're seeing on MountSharp is dramaticallydifferent from what we saw inthe first two years of themission," said CuriosityProject Scientist AshwinVasavada of JPL. "There's somuch variability withinrelatively short distances.The silica is one indicator ofhow the chemistry changed.It's such a multifaceted andcurious discovery, we'regoing to take a while figuringit out."
For more about Curiosity,which is examining sanddunes this month, visit:
http://mars.jpl.nasa.gov/msl/
The Prairie Astronomer 26
To check out one of the club telescopes, contact BethJenckes. If you keep a scope for more than a week,please check in once a week, to verify the location ofthe telescope and how long you plan to use it. Thecheckout time limit will be two weeks, but can beextended if no one else has requested use of a clubscope.100mm Orion refractor: Available
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The Prairie Astronomer is published monthlyby the Prairie Astronomy Club, Inc.Membership expiration date is listed on themailing label. Membership dues are: Regular$30/yr, Family $35/yr. Address all newmemberships and renewals to: The PrairieAstronomy Club, Inc., PO Box 5585,Lincoln, NE 68505-0585. For other clubinformation, please contact one of the clubofficers listed to the right. Newslettercomments and articles should be submitted to:Mark Dahmke, P. O. Box 5585, Lincoln, NE68505 or [email protected], no less than tendays prior to the club meeting. The PrairieAstronomy Club meets the last Tuesday ofeach month at Hyde Memorial Observatory inLincoln, NE.
