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The Prairie AstronomerMarch 2016 Volume 57, Issue #3
MSRAL
The Newsletter of the Prairie Astronomy Club
BrettBoller’sMilky WaySee page 4
March Program:
Mark Ellis: “Space Law”
The Prairie Astronomer
NEXT PAC MEETING: March 29, 7:30pmat Hyde ObservatoryPROGRAMMarch: Space Law Part I - Mark Ellis
The Martian portrayed a positive future for the US Space Program.NASA, with help from China, was able to rescue Mark Watney afterbeing marooned on Mars.
To do this, we saw them use great technology that exists today.But what are the legal implications of interplanetary travel?Attorney Mark Ells, a recent graduate of UNL's Space LawProgram, will explore that topic at the March PAC meeting.
CONTENTS
4 Meeting Minutes
5 2017 Eclipse PlanningMeeting
6 Astrophotography
7 Black Hole RotationRate
9 Mercury’s Crust
11 Observatory Update:IC 239
13 DSLRAstrophotography
17 From the Archives
18 April Observing
19 Focus onConstellations
20 Gravitational WaveAstronomy
22 Ceres Bright Spots(Again)
24 Club Information
Buy the book! The PrairieAstronomy Club: Fifty Yearsof Amateur Astronomy.Order online from Amazon orlulu.com.
FUTURE PROGRAMS
April: Space Law Part II - Elsbeth Magilton & Prof Frans Von der Dunk
June: Solar Star Party
August: NSP Review
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PAC E-MAIL:[email protected]
PAC-LIST:Subscribe through GoogleGroups.To post messages to the list, sendto the address:[email protected]
The Prairie Astronomerc/o The Prairie Astronomy Club, Inc.P.O. Box 5585Lincoln, NE 68505-0585
ADDRESS
EVENTS
Photo by Brian Sivill
2016 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 Meeting
PAC MeetingTuesday March 29th, 2016, 7:30pmHyde Observatory
Astronomy Day, Sunday, April 17 at Morrill Hall
PAC MeetingTuesday April 26th, 2016, 7:30pmHyde Observatory
PAC MeetingTuesday May 31st, 2016, 7:30pmHyde Observatory
Newsletter submission deadline April 16
Star PartyDate
Star PartyDate
Lunar PartyDate
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- Aug 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
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Prairie Astronomy Club
Minutes for the meeting ofFebruary 23, 2016
President Jim Kvasnicka calledthe meeting to order. 11members, 2 guests.
Jim welcomed members andguests to the meeting.
Jim Reviewed upcoming eventsand star parties for the month.
We reviewed the benefits andrequirements of clubmembership.
Jim presented his observingreport for March. The club starparties are March 4th and 11that the Farm.
Club Business:
Astronomy Day is coming upon April 17 from 1:30-4:30. Weneed telescopes for display inMorrill Hall. If anyone would liketo provide a telescope, pleasecontact Zach by March 1.
John Reinert provided thetreasurer's report. The auditwas completed on February 6th
by John, Mike Kearns, RickBrown and Lee Taylor. Johnsummarized the audit for theclub. John is working on aneasier way for themembership to access theroster.
Adjourn to the program on theAstronomical League'sobserving programs.
Respectfully submitted by
Lee Taylor
PAC Meeting Minutes
The new mural has been installed at Hyde Observatory. This photo is a composite of the Milky Waytaken by Brett Boller and Dave Knisely at the Nebraska Star Party in July, 2015.
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March 3, 20165:30 pm, Hyde Memorial Observatory
Present: Lee Thomas, Dan Delzell, Jamie Kelley,Dave Churilla, Guest - Michael Sibbernsen
The group invited Michael Sibbernsen to shareinfo about other solar eclipse events going onthroughout Nebraska on August 21, 2017.
- The Nebraska Eclipse Consortium thisgroup is made up of individuals/agency’sinvolved in planning solar eclipse eventsthroughout the state.
o Lee Thomas will be notified via Sib-bernsen of the next meeting
o There will be a website, it is not ac-tive right now.
▪ Listing of activity locations
▪ Public can go to for informa-tion
o NASA NE Space Grant
▪ Statewide ambassadors
o Distribution of up to 50,000 solareclipse glasses
- In addition to the Eclipse Consortium, Sib-bernsen will be involved, on the day of theeclipse, with the release of a constellationof weather balloons documenting theeclipse.
Updates on activities from Hyde/PAC:- Hyde has ordered 2000 solar glasses.
1000 were ordered in 2014.
- The committee has discussed possiblytrain the trainer workshops for LPS sci-ence teachers and others leading up tothe eclipse.
o The training could be done also viavideo conference or pre-recordedtraining
o Sibbersnsen mentioned that thesetrainings could also be done by theNASA Ambassadors to reach moreindividuals
- The need for a brochure with eclipse andsafe viewing info was discussed.
o Sibbersnsen thinks this is a goodidea
o It would be ideal for the Consortiumto work together on this so that in-formation being distributed is con-sistent
o Brochure should be ready by Janu-ary 1, 2017
- Other media coverage will be needed
o Where and how to view
o Resources available
o Contacts – Hyde/Web
- Promotion of the eclipse can begin
o 5 min presentation as part of Satur-day night program.
- Hyde will be open for the eclipse
o There will need to be a capacity set
o Traffic control will be needed
o At least 10 volunteers will be need-ed
o Exclusive use permits with Parksand Rec will need to be completed
- Other happenings in 2017
o Hyde’s 40th Anniversary
o Nebraska’s 150th
- A chair for the committee is needed
2017 Solar Eclipse Planning Committee Meeting Minutes
Astrophotography by Club Members
Beth Jenckes
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A recent observational campaigninvolving more than two dozenoptical telescopes and NASA'sspace based SWIFT X-raytelescope allowed a team ofastronomers to measure veryaccurately the rotational rate ofone of the most massive blackholes in the universe. Therotational rate of this massive
black hole is one third of themaximum spin rate allowed inGeneral Relativity. This 18 billionsolar mass heavy black holepowers a quasar called OJ287which lies about 3.5 billion lightyears away from Earth. Quasi-stellar radio sources or `quasars'for short, are the very brightcenters of distant galaxies which
emit huge amounts of electro-magnetic radiation due to theinfall of matter into theirmassive black holes.
This quasar lies very close tothe apparent path of the Sun'smotion on the celestial sphereas seen from Earth, wheremost searches for asteroidsand comets are conducted.
Clocking the Rotation Rate of a Supermassive Black Hole
An illustration of the binary black hole system in OJ287. The predictions of the model are verified byobservations.
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Therefore, its optical photometricmeasurements already covermore than 100 years. A carefulanalysis of these observationsshow that OJ 287 has producedquasi-periodic optical outburstsat intervals of approximately 12years dating back to around1891. Additionally, a closeinspection of newer data setsreveals the presence of double-peaks in these outbursts.
These deductions promptedProf. Mauri Valtonen ofUniversity of Turku, Finland andhis collaborators to develop amodel that requires the quasarOJ287 to harbour two unequalmass black holes. Their modelinvolves a massive black holewith an accretion disk (a disk ofinterstellar material formed bymatter falling into objects likeblack holes) while thecomparatively smaller black holerevolves around it. The quasarOJ287 is visible due to the slowaccretion of matter, present inthe accretion disk, onto thelargest black hole. Additionally,the small black hole passesthrough the accretion disk duringits orbit which causes the diskmaterial to heat up to very hightemperatures. This heatedmaterial flows out from bothsides of the accretion disk andradiates strongly for weeks. Thiscauses peaks in the brightness,and the double peaks arise dueto the ellipticity of the orbit, asshown in the figure.
The binary black hole model forOJ287 implies that the smallerblack hole's orbit should rotate,and this changes where andwhen the smaller hole impactsthe accretion disk. This effectarises from Einstein's GeneralTheory of Relativity and its
precessional rate dependsmainly on the two black holemasses and the rotation rate ofthe more massive black hole. In2010, Valtonen andcollaborators used eight welltimed bright outbursts of OJ287to accurately measure theprecession rate of the smallerhole's orbit. This analysisrevealed for the first time therotation rate of the massiveblack hole along with accurateestimates for the masses of thetwo black holes. This waspossible since the smaller blackhole's orbit precess at anincredible 39 degrees perindividual orbit. The GeneralRelativistic model for OJ287 alsopredicted that the next outburstcould occur around the time ofGR Centenary, 25 November2015, which marks the 100thanniversary of Einstein'sGeneral Theory of Relativity.
An observational campaign wastherefore launched to catch thispredicted outburst. Thepredicted optical flare beganaround November 18, 2015 andreached its maximum brightnesson December 4, 2015. It is thetiming of this bright outburst thatallowed Valtonen and his co-workers to directly measure therotation rate of the moremassive black hole to be onethird of the maximum spin rateallowed in General Relativity. Inother words, its Kerr parameteris accurately measured to be0.31 and its maximum allowedvalue in General Relativity isone. In comparison, the Kerrparameter of the final black holeassociated with the first everdirect detection of gravitationalwaves is only estimated to bebelow 0.7.
The observations leading toaccurate spin measurementhave been made due to thecollaboration of a number ofoptical telescopes in Japan,South Korea, India, Turkey,Greece, Finland, Poland,Germany, UK, Spain, USAand Mexico. The effort, led byStaszek Zola of Poland,involved close to 100astronomers from thesecountries. Interestingly, anumber of key participantswere amateur astronomerswho operate their owntelescopes. Valtonen's teamthat developed andcontributed to the spinningbinary black hole modelinclude theoreticalastrophysicist A. Gopakumarfrom TIFR, India, and ItalianX-Ray astronomer StefanoCiprini who obtained andanalyzed the X-ray data.
The occurrence of thepredicted optical outburst ofOJ287 also allowed the teamto confirm the loss of orbitalenergy to gravitational waveswithin two percent of GeneralRelativity's prediction. Thisprovides the first indirectevidence for the existence ofa massive spinning black holebinary emitting gravitationalwaves. This is encouragingnews for the Pulsar TimingArray efforts that will directlydetect gravitational wavesfrom such systems in the nearfuture. Therefore, the presentoptical outburst of OJ287makes a fitting contribution tothe centenary celebrations ofGeneral Relativity and adds tothe excitement of the firstdirect observation of atransient gravitational wavesignal by LIGO.
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Ever since the MESSENGERspacecraft entered orbit aroundMercury in 2011, and indeedeven since Mariner 10‘s flyby in1974, peculiar “dark spots”observed on the planet’s surfacehave intrigued scientists as totheir composition and origin.Now, thanks to high-resolutionspectral data acquired byMESSENGER during the lastfew months of its mission,researchers have confirmed thatMercury’s dark spots contain aform of carbon called graphite,excavated from the planet’soriginal, ancient crust.
Commonly found within andaround impact craters andvolcanic vents, the dark spots onMercury—also referred to as“low-reflectance material,” orLRM—were originally suspectedto contain carbon delivered tothe planet by comets.Data from MESSENGER’sGamma-Ray and NeutronSpectrometer (GRNS) and X-rayinstruments confirmed the LRMto contain high amounts ofgraphitic carbon, but likelyoriginating from within Mercuryitself. It’s thought that Mercurywas once covered by a crustcomposed of graphite, when
much of the planet was stillmolten.“Experiments and modelingshow that as this magmaocean cooled and mineralsbegan to crystallize, mineralsthat solidified would all sinkwith the exception of graphite,which would have beenbuoyant and would haveaccumulated as the originalcrust of Mercury,” said RachelKlima, co-author of a recentstudy on LRM and a planetarygeologist at the Johns HopkinsUniversity Applied PhysicsLaboratory. “We think that LRMmay contain remnants of this
Dark Stains on Mercury Reveal Its Ancient Crust
Jason Major, Universe Today
Expanded-color image of Mercury's 52-km Degas crater, showing an abundance of low-reflectancematerial (LRM).
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primordial crust. If so, we may beobserving the remains ofMercury’s original, 4.6-billion-year-old surface.”Although similar in visiblecoloration and covered incraters, cracks, and mountains,any similarities between Mercuryand other smaller worlds in ourSolar System—including ourMoon—end there. Mercury has aformation history all it own and iscompositionally unique amongthe planets.These data revealing such arelatively high concentration ofgraphite in Mercury’s crust onlyadds to those differences, andalso tell us about the variouselements that were presentaround the Sun when the planetswere forming.“The finding of abundant carbonon the surface suggests that wemay be seeing remnants ofMercury’s original ancient crustmixed into the volcanic rocks andimpact ejecta that form thesurface we see today,” said LarryNittler, research paper co-authorand Deputy Principal Investigatorof the MESSENGER mission.“This result is a testament to thephenomenal success of theMESSENGER mission and addsto a long list of ways theinnermost planet differs from itsplanetary neighbors andprovides additional clues to theorigin and early evolution of theinner Solar System.”
On Earth graphite is used inindustry to make bricks that linerefractory furnaces and increasethe carbon content of steel. It’salso widely used in fireretardants, batteries, andlubricants, and is mixed with clayin various amounts to create the“lead” in pencils (which, by theway, contain no actual lead.)These findings have beenpublished in the March 7, 2016Advanced Online Publication ofNature Geoscience.MESSENGER (MErcury Surface,Space ENvironment,GEochemistry, and Ranging)was a NASA-sponsored scientificinvestigation of the planetMercury and the first spacemission designed to orbit the
planet closest to the Sun. TheMESSENGER spacecraftlaunched on August 3, 2004,and entered orbit aboutMercury on March 17, 2011(March 18, 2011 UTC). OnApril 30, 2015, after four yearsin orbit MESSENGER‘smission and operational lifecame to an end when itimpacted the surface ofMercury in its northern polarregion.
Source: Carnegie Science andJHUAPL
Low-reflectance material surrounding an 80-km crater calledBasho, imaged in May 2012
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IC 239 is a low surfacebrightness spiral that isconsidered part of the NGC1023 group. NGC 1023 is Arp135 and is located about 45minutes of arc east of IC 239. Itis located in far easternAndromeda while NGC 1023 isin Perseus. The distance toboth is highly controversial. Asa member of the 1023 group itshould be at approximately thesame distance. When I took Arp135 back in October of 2008 Iput it at 20 million light-years.That isn't likely correct. Whilecurrent distance estimates for
Arp 135 seem to collect around32 to 34 million light-yearsvalues down to the 20 millionlight-years I used and up to 64million light-years are found inthe reasonably currentliterature. I'll go with 32 millionlight-years simply because thatis also the redshift value for IC239. Using that distance theseparation of IC 239 from Arp135 is only 430,000 light-yearsso it is possible that IC 239 isfeeling the tidal forces of the farmore massive Arp 135. Indeedit shows faint extended arms orplumes to the north and south.
Attempts toget a Tully-Fisherdistanceestimate arebugged by notbeing able todetermineexactly howface on we are seeing it. Twodifferent methods of determiningthis give two very differentanswers. With so manyuncertainties it is possible, butunlikely the two aren't related.My post about NGC 1023/Arp135 with its likely too close
Observatory Update: IC 239Rick Johnson
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distance estimate can be seenhere.
NED classifies IC 239 asSAB(rs)cd LINER2. Thisindicates something may have
shaken up the core black hole toa rather active state. That maybe Arp 135. Assume the 32million light-year distance I get asize of about 42,000 light-yearsand that includes the plumes.
Ignoring them it is 30,000 light-years in size. So not only is it asmall spiral it's low surfacebrightness indicates few starsfilling what little volume it takesup. As such it shouldn't be hard
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for a larger companion to distortit as appears to havehappened. Though if it has aton of dark matter we can't seeall this is moot.
It was discoveredphotographically by IsaacRoberts in 1893 using the 20"reflector at his observatory"Starfield", Crowborough Hill,Sussex, UK. He put it inPerseus though at that time the
constellation borders were notwell defined and it may wellhave been in that constellationby the boundaries is use at thetime. Today it is only inAndromeda by 28 arc minutes.
There is only one other obviousgalaxy in my image, PGC2802360 to the east. Anothervery low surface brightnessgalaxy. No distance informationis available at NED. It may be a
dwarf member of the group. Infact it's other catalog name isNGC 1023 GROUP:[TT2009]18. That, I've found, doesn'tcount for much as galaxieslabeled as members of othergroups often have redshifts thatput them billions of light-yearsfrom the cluster whose namethey carry. With nothing worthannotating but for IC 239 I didn'tprepare an annotated image.
With DSLRs and standardcamera lenses astrophotographyis on the verge of a new epoch,where tracking is no longerabsolutely mandatory. When weheard about the techniquedescribed in this article, weimmediately wanted to give it atry. It allows any stargazer usinga modern DSLR to capturecolorful, noise-free images ofdeep-sky objects, without anequatorial mount or trackingdevice needed.
How it Works
The technique described herewas originally brought to ourattention by our fellow observerWolfgang Vollmann, who hasbeen using it for some time tocapture comets. His initialresults were promising and wedecided to give it a closer lookand develop it further wherepossible. After a series ofexperiments we are now able topresent a tried and testedworkflow that guarantees greatimages of star fields. The basicidea of the method is actuallyquite simple: Shoot a lot of
similar exposures at very highISO ratings and keep the singleexposures so short that notracking is needed. Theindividual frames can then bedigitally combined in a stackingprogram to create a final picturethat shows faint details and isfree of the noise that comes withthe high ISO setting. As the
sample images show, theresults are quite astounding.For example, with a 135mmlens we captured detailedimages of star clusters andnebulae, reaching a limitingmagnitude of 14mag. Imagesshot with a 50mm lens easilycaptured star clouds and
DSLR Astrophotography UntrackedKaroline Mrazek and Erwin Matys, Project Nightflight
The Great Sagittarius Star Cloud, imaged with a 50mm lenswithout tracking. All images were captured under the pristineskies of La Palma island. See text for exposure details.
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nebulae in the Milky Way withgreat detail.
What You Need
The imaging method is verysimple and therefore instrumentrequirements are minimal. Firstof all, you will need one of thelater DSLR models that allowISO settings of 6400 or higher.As a lens, any wide angle,standard or tele lens will do,even the typical kit zoom lenseswill work. A small but sturdytripod is required for mountingand pointing the camera. Forfield work at remote sites werecommend the new, lightweightmodels (<0.5kg) with a ball headthat are available from severalmanufacturers. The lastmandatory item is a remoterelease timer that allows you toprogram a series of exposures.As an alternative, many of the
newer DSLR models can beremote controlled via asmartphone app. Additionally,you might want to use a right-angle viewfinder and a lenshood. As the shopping listshows, any astrophotographeror nature-interested terrestrialphotographer will probablyalready own most of theseitems. For this reason themethod is ideal for casualastrophotography to capture acomet, a nova or simply to takesome pictures of your favoritedeep-sky objects during avacation at a dark site.
How to Shoot
First of all, shoot at the darkestlocation and under the bestskies you have access to. Thiswill guarantee that the individualexposures already show thebest contrast possible. After
setting up your equipment, setthe DSLR's picture mode toRAW, white balance todaylight and sensitivity to ISO6400 or higher. Turn off anypresets for noise reduction,sharpening or colorenhancement. Switch yourlens to manual focus and usemagnified live mode to focusyour lens on a brighter star.Finally, step down your lensat least one f-stop from wideopen. This will reduce lensaberrations noticeably,especially when using a zoomlens. The next step is toprogram your remote releasetimer for a greater number ofexposures, 100 is a goodvalue to start with. When youset the exposure time for theindividual frames, be awarethat it is limited by the focallength of your lens. With a50mm lens, 3-secondexposures are fine, with a135mm lens exposure timeshould be around 1 second.To determine the maximumexposure time for yourspecific DSLR and lens moreprecisely, use the formulagiven in the workflow tutorialthat is available for freedownload (see link at the endof the article). If you keepyour exposure times withinthe specified limits, the starson your pictures will be niceand round without any signsof trailing. As soon as youhave completed these steps,your camera is ready and it istime to frame your target.Point your DSLR at the starfield, nebula or comet youwant to image. Place theobject slightly off center in thecamera's viewfinder, so it willdrift over the center duringyour exposure series. Start
Typical setup for untracked astrophotography; instrumentrequirements are minimal. All you need is a DSLR, a tripod and aremote release timer. You may want to add a lens hood and aright-angle viewfinder.
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your timer and let your camerarecord the target. Once theexposure series is finished,cover your lens and shoot atleast 10 dark frames with thesame exposure settings. To giveyou an idea which settings workwell, the images accompanyingthis article were shot at ruralsites on La Palma Island with aCanon 1100D body set at ISO6400 with series of 100exposures each. We used a50mm lens @f/2.8 and a 135mmlens @f/4 with 3 and 1 secondexposures, respectively. Exceptthat our Canon 1100D ismodified for optimum H-alphasensitivity, it is an ordinary, off-the-shelf APS-C sized camerabody. Although an unmodifiedDSLR will record less rednebulosity it will still work verywell for the method described.
Processing the Images
Once you return from yourimaging trip, star party, vacationor camping hike, it is time todevelop the final images. As wementioned above, the magicunfolds with the stacking of theindividual exposures. Thisprocedure cancels out the noiseof the high ISO setting andenhances faint details as well assmall stars. For the task ofstacking the images there aremany different programsavailable. We recommend thewidely used freeware Deep SkyStacker to start with, but anyother stacking software will dothe job as well (For tips on theparameter settings in Deep SkyStacker follow the link to thetutorial at the end of the text).With the stacking software ofyour choice, simply import yourexposure series as well as thedark frames and let the program
register and digitally combinethe individual frames. The resultis a calibrated stack of yourimages that is practically noise-free. To get the maximum out ofyour resulting image you willthen have to enhance it using an
image processing softwaresuch as Photoshop.
Some Final Thoughts
As our experiments show,tracking is no longer anabsolute requirement forstunning star field images. But
Omega Centauri Cluster, imaged with a 135mm lens withouttracking. Limiting magnitude is 14mag, see text for exposuredetails.
Deneb and the North America Nebula, imaged with a 50mm lenswithout tracking. See text for exposure details.
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don't get us wrong: A stack ofshort untracked shots is nosubstitute for a stack of trackedlong exposures, which will havea better signal-to-noise ratio inany case. Nevertheless, we findit very interesting how far amodern DSLR can go withoutany tracking. And with DSLRcameras getting more and moresensitive, this is only thebeginning. As far as we can tell,even today there are a lot ofpossible applications for thismethod of untracked DSLRastrophotography. To name onlya few:
- The technique is so simplethat even beginners toastrophotography will easilymaster it. Therefore, it is nolonger mandatory to buy anequatorial mount or sky trackerto get started withastrophotography.
- Instrument requirements ofuntracked DSLRastrophotography are minimal.Photographers who want totravel light to dark locations willhave less weight to carry withthem.
- The method is ideal in allsituations when thephotographer doesn't want tohassle with the complexitythat comes with the use of anequatorial mount or trackingdevice.
The authors Karoline Mrazekand Erwin Matys are foundingmembers of theastrophotography groupproject nightflight. Check outtheir images, tests and toolsat www.project-nightflight.net
Orion Nebula M42, imaged with a 135mm lens.The colorful and noise-free picture is the resultof a stack of 100 single exposures.
Scutum Star Cloud, imaged with a 50mm lenswithout tracking. Short focus lenses workespecially well for capturing Milky Way vistas likethis one. See text for exposure details.
Download the Tutorial
A compact tutorial of the workflow described canbe downloaded from the tests & tools section onour website. We prepared the tutorial for allfellow photographers, because this methodprovides an easy way to capture star fields,nebulae, star clusters, Milky Way regions andeven binocular comets with minimal equipment.The full article, including the workflow tutorial canbe downloaded here.
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From the Archives: March, 1976
Comet West – Brilliant,Unexpected Maverick – Nowis it Comets West?
Aside from its unanticipatedbrilliance (consistently one totwo magnitudes brighter thaninitial predictions), Comet Westhas managed to command theattention of professionals andamateurs with some interestingantics in the morning sky.
Its prominent tail has, on closeobservation, been seen toinclude a broad dust tailcomposed of a number of“synchronic bands‘, accordingto Z. Sekanina of the Center forastrophysics. “The bandsshowed a systematictranslational motion of about1.60 per day and rotated atabout 13° per day relative to thefaint plasma tail, one of themessentially coinciding with itssouthern border." On a printobtained March 5, Sekaninanoted as many as 20"synchronic bands‘, the mostdistant of which reached as faras 19 degrees from thenucleus,with "the dust tailextending to some 25 degrees.Sekanina explained that thedust tail was composed ofpostperihelion particleemissions, while a faint sectionnortheast of the nucleus wasmade up of somewhat heavierparticles emitted during theweek before perihelion.
Brian G. Marsden of theSmithsonian AstrophysicalObservatory speculated duringthe week of March 15 thatComet West might have brokenup into a main cometarynucleus and as many as threesmaller nuclei. Visualobservations beginning March 5indicated secondary nuclei atp.a. 50 degrees, separation 3",magnitude difference 0.5;another at 120 degrees,magnitude 0, no separationdata; and one at 350 degrees,separated by about 4",magnitude difference 0.5.Reliable estimates on CometWest indicated a magnitude of-3.65 shortly after perihelion onFebruary 26, viewed during
daylight. The comet declined tomagnitude 0 by March 3,approximately magnitude 1 onMarch 6, and was still atmagnitude 1.8 late on March 5.Original predictions were thatWest should have been downto magnitude 3.2 on the 8th--so,given its rapid advance intodark skies, providing contrast,and its retained brilliance,Comet West was turning out tobe everything Kohoutek wasn't.
Comet West was discovered in photographs by Richard West on August 10, 1975. It reached peakbrightness in March 1976. During its peak brightness, observers reported that it was bright enough tostudy during full daylight. Despite its spectacular appearance, it did't cause much expectation amongthe popular media. The comet has an estimated orbital period of 558,000 years. Photo credit: J.Linder/ESO. [Source: Wikipedia]
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This is a partial list of objects visible for theupcoming month.
PlanetsMercury: Low in the WNW shining as bright as-1.5 in early April.Jupiter: Shines at magnitude -2.3 with a disk 41”wide.Mars and Saturn: The two form a pair justabove Antares. Mars rises around midnight withSaturn 40 minutes later. Mars increases inmagnitude from -0.6 to -1.4. This is the largestMars will appear in the last 10 years with a disk16” wide.Venus: Rises just a half hour before the Sun andafter April 9th is not visible.Uranus and Neptune: Both are not visible inApril.
Meteor ShowersLyrids: Peaks at 2:00 am the morning of April22nd. This weak shower will be impacted by thefull Moon.
Messier ListM40: Multiple star in Ursa Major.M65/M66: Galaxies in the Leo Triplet Group.M95/M96: Galaxies in Leo that fit in the sameFOV.M105: Galaxy in Leo.M106: Galaxy in Canes VenaticiM108: Galaxy in Ursa Major.M109: Galaxy in Ursa Major.Last Month: M41, M44. M46, M47, M48, M50,M67, M81, M82, M93Next Month: M49, M51, M61, M63, M64, M85,M94, M101, M102, M104
NGC and other Deep SkyObjectsNGC 2841: Galaxy in UrsaMajor.NGC 2903: Galaxy in Leo.NGC 3184: Galaxy in UrsaMajor.NGC 3242: The Ghost ofJupiter in Hydra.NGC 3384/NGC 3389:Galaxies in the same FOV with M105 in Leo.NGC 3521: Galaxy in Leo.
Double Star Program ListAlpha Leonis: Regulus, white primary with apale yellow secondary.Gamma Leonis: Algieba, pair of yellow stars.54 Leonis: Yellow primary with a greenishcolored secondary.Alpha Canum Venaticorum: Cor Caroli, blue-white and greenish yellow pair.Zeta Ursa Majoris: Mizar, white pair.Gamma Virginis: Porrima, close pair of yellowstars.24 Comae Berenices: Yellow primary with apale blue secondary.Delta Corvi: White and rose colored pair.
Challenge ObjectNGC 3995 Group: The brightest member in atrio of galaxies in Ursa Major. Other galaxiesinclude NGC 3991 and NGC 3994.
April Observing: What to ViewJim Kvasnicka
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Leo
Leo, the Lion is one of the most distinctiveconstellation patterns in the sky. The head andforequarters of the Lion are marked by theasterism called the sickle. Leo, as is typical ofconstellations off the Milky Way, contains manygalaxies. A number of them are large and bright.Leo contains five galaxies with Messier numbers:M65, M66, M95, M96, and M105. Theconstellation contains several interesting doublestars. One of them Algieba, Gamma Leonis, isone of the finest double stars in the sky. Leocontains the radiant of the Leonid meteor showerwhich peaks every year around November 17th.The constellation Leo is best seen in April.
Showpiece Objects
Galaxies: M65, M66, M95, M96, M105, NGC2903, NGC 3521, NGC 3628Multiple Stars: Alpha Leonis (Regulus), GammaLeonis (Algieba), 54 Leonis, 88 Leonis
Mythology
In Greek mythology the celestial Lion wasassociated with the Nemean Lion slain byHercules as the first of his Twelve Labors. TheGreeks inherited the Lion from the Babyloniansbefore them. A common theme in Babylonian artis a battle between a Lion and a Bull with the Lionalways defeating the Bull.
Number of Objects Magnitude 12.0 andBrighter
Galaxies: 58
Focus on Constellations: LeoJim Kvasnicka
Photo: Till Credner - Own work: AlltheSky.com
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Gravitational Wave Astronomy Will Be The Next Great Scientific Frontier
Ethan Siegel
Imagine a world very differentfrom our own: permanentlyshrouded in clouds, where thesky was never seen. Never hadanyone see the Sun, the Moon,the stars or planets, until onenight, a single bright objectshone through. Imagine thatyou saw not only a bright pointof light against a dark backdropof sky, but that you could see abanded structure, a ringedsystem around it and perhapseven a bright satellite: a moon.That's the magnitude of whatLIGO (the Laser InterferometerGravitational-waveObservatory) saw, when itdirectly detected gravitationalwaves for the first time.
An unavoidable prediction ofEinstein's General Relativity,gravitational waves emergewhenever a mass getsaccelerated. For most systems-- like Earth orbiting the Sun --the waves are so weak that itwould take many times the ageof the Universe to notice. Butwhen very massive objects orbitat very short distances, theorbits decay noticeably andrapidly, producing potentiallyobservable gravitational waves.Systems such as the binarypulsar PSR B1913+16 [the
subtlety here is that binarypulsars may contain a singleneutron star, so it’s best to bespecific], where two neutronstars orbit one another at veryshort distances, had previouslyshown this phenomenon oforbital decay, but gravitationalwaves had never been directlydetected until now.
When a gravitational wavepasses through an objects, itsimultaneously stretches andcompresses space alongmutually perpendiculardirections: first horizontally,then vertically, in an oscillatingfashion. The LIGO detectorswork by splitting a laser beaminto perpendicular “arms,”letting the beams reflect backand forth in each arm hundredsof times (for an effective pathlengths of hundreds of km), andthen recombining them at aphotodetector. The interferencepattern seen there will shift,predictably, if gravitationalwaves pass through andchange the effective pathlengths of the arms. Over aspan of 20 milliseconds onSeptember 14, 2015, bothLIGO detectors (in Louisianaand Washington) saw identicalstretching-and-compressing
patterns. From that tiny amountof data, scientists were able toconclude that two black holes,of 36 and 29 solar massesapiece, merged together,emitting 5% of their total massinto gravitational wave energy,via Einstein's E = mc2.
During that event, more energywas emitted in gravitationalwaves than by all the stars inthe observable Universecombined. The entire Earth wascompressed by less than thewidth of a proton during thisevent, yet thanks to LIGO'sincredible precision, we wereable to detect it. At least ahandful of these events areexpected every year. In thefuture, different observatories,such as NANOGrav (whichuses radiotelescopes to thedelay caused by gravitationalwaves on pulsar radiation) andthe space mission LISA willdetect gravitational waves fromsupermassive black holes andmany other sources. We've justseen our first event using a newtype of astronomy, and can nowtest black holes and gravity likenever before.
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!
The Prairie Astronomer 21
Image credit: Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al.,(LIGO Scientific Collaboration and Virgo Collaboration), Physical Review Letters 116, 061102 (2016).This figure shows the data (top panels) at the Washington and Louisiana LIGO stations, the predictedsignal from Einstein's theory (middle panels), and the inferred signals (bottom panels). The signalsmatched perfectly in both detectors.
Gravitational Wave Astronomy, continued.
The Prairie Astronomer 22
All right, maybe not blinking likea flashlight (or a beacon on thetippity-top of a communicationtower—don’t even start thatspeculation up) but the now-famous “bright spots” on thedwarf planet Ceres have beenobserved to detectably increaseand decrease in brightness, ifever-so-slightly.
And what’s particularlyinteresting is that theseobservations were made not byNASA’s Dawn spacecraft,currently in orbit around Ceres,
but from a telescope right hereon Earth.
Researchers using the HighAccuracy Radial velocity PlanetSearcher (HARPS) instrumenton ESO’s 3.6-meter telescope atLa Silla detected “unexpected”changes in the brightness ofCeres during observations inJuly and August of 2015.Variations in line with Ceres’ 9-hour rotational period—specifically a Doppler effect inspectral wavelength created bythe motion of the bright spots
toward or away from Earth—were expected, but otherfluctuations in brightnesswere also detected.
“The result was asurprise,”said Antonino Lanzafrom the INAF–CataniaAstrophysical Observatory,co-author of the study. “Wedid find the expected changesto the spectrum from therotation of Ceres, but withconsiderable other variationsfrom night to night.”
The Bright Spots on Ceres Are Blinking
Jason Major, Universe Today
Bright reflective material in Ceres' Occator crater, imaged by NASA's Dawn spacecraft in Sept .2015.Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
The Prairie Astronomer 23
Watch a video below illustratingthe rotation of Ceres and howreflected light from the brightspots within Occator crater arealternately blue- and red-shiftedaccording to the motion relativeto Earth.
First observed with Hubble inDecember 2003, Ceres’ curiousbright spots were resolved byDawn’s cameras to be a clusterof separate regions clusteredinside the 60-mile (90-km) -wideOccator crater. Based on Dawndata they are composed of sometype of highly-reflective materialslike salt and ice, although theexact composition or method offormation isn’t yet known.
Since they are made of suchvolatile materials though,interaction with solar radiation islikely the cause of the observeddaily brightening. As thedeposits heat up during thecourse of the 4.5-hour Ceresdaytime they may create hazesand plumes of reflectiveparticles.
“It has been noted that the spotsappear bright at dawn on Cereswhile they seem to fade bydusk,” noted study lead authorPaolo Molaro in the team’spaper. “That could mean thatsunlight plays an important role,for instance by heating up icejust beneath the surface andcausing it to blast off some kindof plume or other feature.”
Once day turns to night thesehazes will re-freeze,depositing the particles backdown to the surface—although never in exactly thesame way. These slightdifferences in evaporation andcondensation could explainthe random variation in dailybrightening observed withHARPS.
These findings have beenpublished the journal MonthlyNotices of the RoyalAstronomical Society (full texton arXiv here.)
Source: ESO
Youtube link: https://www.youtube.com/watch?v=AN9MxTDyqww
The Prairie Astronomer 24
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