National Capital Astronomers, Inc.

Volume 56, Number 4

Phone: 301/565-3709

ISSN 0898-7548

Stars in the Laboratory: Presolar Grains in Meteorites

The next meeting of the National Capi-tal Astronomers will be held on Satur-day, December 6 at 7:30 P.M., in theLippsett Auditorium on the main floorof the Clinical Center (Building 10) atthe National Institutes of Health (NIH).Larry R. Ninler of the Carnegie Institu-tion of Washington, Department ofTer-resiriaJ MagnetIsm win speak on "Starsin the Laboratory: Presolar Grains inMeteorites." The speaker sent the fol-lowing abstract and biography:

Primitive meteorites contain grainsof "stardust." These tiny specks of dust

formed in the winds of ancient stars onin supernova explosions and becamepart of the cloud from which the Sun andplanets formed. The chemical and iso-topic compositions of these grains re-flect those of their stellar sources. Theythus serve as probes of the physicalconditions inside stars and in supernovaejecta. Presola, grains identitied so farinclude SiC, diamond, graphite, siliconnitride, A1203, and MgAIP4' This talkwill discuss how these grains are iso-lated from meteorites and analyzed inthe laboratory, and how they provide

information about stellar and galacticevolution, stellar nucleosynthesis of theelements and processes in interstellarspace and the early Solar System.

Larry Nittler received a B.A. inphysics from Cornell University in 1991and a Ph.D., also in physics at Washing-ton University in 81. Louis in 1996.Since then, he continued his studies ofpre solar grains in meteorites via apostdoctoral fellowship at the CarnegieInstitution. Injest, Larry Nittler refers tohimself as "Interstellar Dust Buster andMushroom Chief." 0

STScI-PRC95-20BA PIECE OF THEASTEROID VESTAThis meteorite is a sample of the crust of the asteroid Vesta,which is only the third solar system object beyond Earthwhere scientists have a laboratory sample (the otherextraterrestrial samples are from Mars and the Moon). Themeteorite is unique because it is made almost entirely of themineral pyroxene, common in lava flows. The meteorite'smineral grain structure also indicates it was once molten,and its oxygen isotopes are unlike oxygen isotopesfoundforall other rocks of the Earth and Moon. The meteorite'schemical identity points to the asteroid Vesta because it hasthe same unique spectral signature of the mineral pyroxene.111e meteorite also has the same pyroxene signature as othersmall asteroids, recently discovered near Vesta. that areconsidered "chips" blasted off Vesta 's surface. This debrisextends all the way to an "escape hatch" region in the asteroid belt called the Kirkwood gap. This region is swept free ofasteroids because Jupiter's gravitational pull removes material from the main belt and hurls it onto a new orbit that crossesEarth's path around the Sun. The meteorite probably followed this route to Earth. It was tom off Vesta's surface as part ofa larger fragment. Subsequent collisions broke apart the parent fragment and threw pieces toward the Kirkwood gap and

CllfendiJr of fMontnlj (Er;ents

Mondays, December 1, 8, 15,22, and 29, 7:30 PM-Public nights at U.S. Naval Observatory (USNO), inNorthwest Washington, D.C. (off Massachusetts Av-enue). Includes orientation on USNO's mission,viewing of operating atomic clocks, and glimpsesthrough the finest optical telescopes in the Washing-ton-Baltimore region. Held regardless of cloud cover.Information: USNO Public Affairs Office, 202/762-1438. Home page: http://www.usno.navy.mil.

Tuesdays, December 2,9, 16,23, and 30, 7:30 PM-Telescope making classes at Chevy Chase Commu-nity Center, Connecticut Avenue and McKinleyStreet, NW. Information: Jerry Schnall, 202/362-8872.

Saturday, December 6, 5:30 PM-Dinner with thespeaker and other NCA members at the North ChinaRest~urant 0.ll Old Georgetowm Pike. Bethesda, MD.See map and directions on back page.

Saturday, December 6, 7:30 PM-NCA meeting, willfeature Larry R. Nittler, Department of TerrestrialMagnetism, Carnegie Institution, speaking on "Starsin the Laboratory: Presolar Grains in Meteorites." Fordirections, see map and directions on back page.

Volunteers Needed ForThe Astroscout Program

TheNationalPark Service is looking forvolunteerswhoare willing to assist withan astronomy program called"Astroscout." The National Park Ser-vice at the Rock Creek Park NatureCenter and Planetarium is offering toBoy Scouts a free, exciting new pro-gram to learn about astronomy. A mul-timedia introduction to the night sky,this program consists of a planetariumshow, a video, instruction in astronomy,and a viewing of the night sky throughtelescopes. Interested Boy Scouts willbe able to start the Astronomy MeritBadge at this event.

Fridays, December 5,12,19, and 26, 7:30 PM-Tele-scope making classes at American University,McKinley Hall Basement. Information: Jerry Schnall,202/362-8872.

Fridays, December 5, 19, and 26, 8:30 PM-Opennights with NCA's Celestron-14 telescope atRidgeview Observatory; near Alexandria, Virginia; .6007 Ridgeview Drive (off Franconia Road betweenTelegraph Road and Rose Hill Drive). Information: BobBolster, 703/960-9126. Call before 6:00 PM.

During questionable weather, call the IOTA Hotline(Phone: 3011474-4945) for NCA meeting status. Theabsence of a cancellation notice on the Hotline means themeeting will take place.

See page 8 for more Washington area astronomicalevents. Other events too numerous to list in Star Dust arelisted in the publications Sky &: Telescope, the Astro-nomical Calendar 1997, the Observer's Handbook1997, in numerous software packages, and other linksavailable on the NCA Home Page (see above for ad-dress). NCA members can purchase all these (and muchmore) at a discount. To join NCA, use membershipapplication on page 9.

Volunteers with telescopes areneeded from 5:45 PM to 7: 15 PM onSaturday, December 13 1997 to bringtheir telescopes to Military Field at thecomer of Military and Glover Roads forthe scouts to view the stars and otherinteresting phenomena.

The Rock Creek Nature Center andPlanetarium is located in Rock CreekPark at 5200 Glover Road NW. Wash-ington DC 20015. If you have anyquestions or would like to volunteer,please call Ranger Blaine Eckberg at(202) 426-6829. 0

Bishop Claggett Center inBuckeystown. Maryland. needs volun-teers to lead astronomy workshops formiddle school students and their fami-lies on December 29-31. If you canvolunteer on anyone of these days,please contact Donna Kerner, Director.Youth Programs via e-mail atbishclag@erols.com.

The Next Generation Space Telescopeby Wayne H. Warren Jr.

At the October 4, 1997 monthly meet-ing, NCA members and guests werepleased to hear a lecture entitled "Seeingthe First Objects with the Next Genera-tion Space Telescope" given by Dr.John C. Mather of the Laboratory forAstronomy and Solar Physics, NASAGoddard Space Flight Center. Dr.Mather is well-known to longtime NCAmembers, having given us a lectureabout the COsmic Background Ex-plorer (COB E) on December 4, 1982.Shorter-term members may be familiarwith his COBE work as well through themany articles and scientific papers thathe has published on the subject. Havingbeen outstandingly successful with theCOBE project, Dr. Mather has beenentrusted with the initial responsibilitiesfor NASA's most "visible" project to flyin the first decade of the new millen-nium.

Dr. Mather began by reminding usthat there are many things that astrono-mers (and many other people as well)would like to know about the Universeand still don't. Over the last decade orso, we have made tremendous progressin our quest for astronomical and astro-physical knowledge. Sophisticatedground-based telescopes and by spacemissions such as NASA's COBE,Hubble Space Telescope (HST),Compton Gamma-Ray Observatory(CGRO), International Ultraviolet Ex-plorer (IUE), and Rossi X-Ray TimingExplorer (RXTE), plus ESA's HIghPrecision PARallax Observing Satellite(HIPPARCOS), have contributed to ourknowledge. But as much as we learn,there are still many things about whichwe remain rather ignorant, and newknowledge often leads to more ques-tions.

Our current understanding, al-though there are alternative views, isthatthe Universe began (or began again)with the so-called "Big Bang" about 13billion years ago (also written 13 x 109

years or 13 Ga). As the Universe ex-panded and cooled, the original opaqueplasma became transparent at about age3 x 1()5years. As we look outwardtoward the edge, as we did using theCOBE satellite, we see structure that weinterpret as ripples in the space-time

continuum. The COBE map of thegravitational field shows an anisotropyof about I part in 105. Weare uncertainabout how critical this anisotropy is andwhether or not the Universe would haveevolved in the same way if completelyisotropic or if anisotropic to a differingdegree. There is evidence that theclumpiness caused matter to eventuallycombine to form galaxies.

The Universe continued to expandfor perhaps 100 Ma before the first gal-axies began to form. The period thatfollowed, between the formation of thefirst galaxies and essentially what wesee today when we look back with HSTto about 40 percent to the edge, is whatwe call the dark age, about which weknow practically nothing. We do notknow why galaxies formed, when orhow they formed, or very much abouthow they evolved. We don't reallyknow what triggered first generationstar formation, although we have lots ofevidence and some understanding of thestar formation process. We believe thatbetween 90 and 99 percent of all matterin the Universe is invisible to us (the so-called "dark matter"), as determinedfrom the rotation curves of galaxies bythe pioneering work of NCA memberVera Rubin. We have pretty good ideasabout the life cycles of stars, at least thatthey form primarily in spiral arms ofgalaxies, they evolve through differentregions of the Hertzsprung-Russell (H-R) diagram according to their changingphysical conditions, until they run out ofnuclear fuel and contract to white

dwarfs (as will the Sun) or explode assupernovae to become burned out neu-tron stars or black holes. The materialejected during these phenomena even-tually condenses to form the next gen-eration of stars, enriched with heavyelements synthesized during the explo-sive stages of the previous generation.This same material condenses to formplanets, asteroids, comets, etc., which

Astronomical Calendarsfor 1998

I am again volunteering to place a bulkorder for Guy Ottewell' s AstronomicalCalendar, but the procedure will beslightly different this year because ittook 3-4 months before I was able todeliver the orders last year and a fewpeople even had to make special trips tomy house, as I did theirs. The discountis substantial for orders of four or more,viz.therel!u1ar "rice is $19.95 + $3.• _. L. _ - - ".

(S&H) = $22.95 each, while the dis-count price is $15.96 + $4. (total). Tokeep things simple, I will collect $17.00for each copy at the December NCAmeeting, so please bring payment withyou. If we have fewer than four orders,there will be no discount and I willwithdraw from service, in which casewe can order individually. If we haveconsiderably more than four orders, Iwill refund according to the final cost.

VESTA Caption, Continued from page 1

onto a collision course toward Earth.Thefragment'sjourney ended in 1960when itfell in Western Australia.NASA's Hubble Space Telescopeobservations further confirm thisscenario by revealing a giant impactbasin on the 325-mile (525 km)diameter asteroid. The ancient impactwas so powerful, it tore off a piece ofthe asteroid's crust, exposing a deepermantle of rock. Most of the identifiedmeteorites from Vesta are in the careof the Western Australian Museum.

This 1.4 pound (631 gm) specimencomes from the New EnglandMeteoritical Services. It is a completespecimen measuring 3.7 inch x 3.1inch x 3.4 inch (9.6 cm x 8.1 cm x 8.7cm) showing the fusion crust, evidenceof the last stage in its journey toEarth. Photo Credit: R. Kempton(New England Meteoritical Services)

~ Don't throw this newsletter~ away. If you're finished with

. it, pass it on to someone else toread or recycle it. It's right for as-tronomy and the environment.

eventually yield such things as rocks,minerals, organic chemicals and, in thecase of the Solar System, such things aswe like to think of as intelligent beingswho can study these phenomena. Onething that we can be sure of is thatvirtually all of the materials that weencounter every day originated in somesupernova explosion that occurredsomewhere in the Milky Way more than5 Ga ago.

We'd really like to know moreabout the details of this evolutionaryprocess, especially about the end pro-cesses that result in the highly con-densed objects mentioned above. Doblack holes disintegrate? Is interstellarspace littered with the burned out cin-ders of black dwarfs and neutron stars?What fraction of dark matter do thesecinders represent? What about thelarge-scale structure of the Universe?What is its actual shape, if such a thingcan even be defined? The Universe isexpanding, but what is it expandinginto? Is space being created at the edge?We hope to be able to answer at leastsome of these profound questions withthe next generation of space-borne mis-sions that will be flown by NASA, ESA,and possibly other space agenciesaround the world.

NGST And Other Planned MissionsDr. Mather briefly describe some of theplanned NASA missions. The NGSTwill be designed to study the dark regionmentioned earlier. It will tentatively belaunched in 2007. There is a SpaceInterferometry Mission (SIM), sched-uled for launch in 2005, primarily de-signed to detect extrasolar planets. Themission's extremely high resolutionwill afford us the opportunity to mea-sure the distances of stars on the otherside of the Galaxy to ±IO% accuracy.We might think of thi!; mission as thesuccessor to HIPPARCOS, although theEuropeans have another astrometricmission on the drawing board for the2000-2002 time frame. Farther downthe line, perhaps in the 2012-2020 timeframe, depending on how soon we canfigure out how to do it, would be amission to take spectra of extrasolarplanets to detect the presence of gaseousatmospheric constituents such a meth-ane, CO2, water vapor, etc. This might

eventually be followed by extrasolarplanetary weather mapping if such athing is ever possible, but that wouldalmost certainly be at least several gen-erations away.

Dr. Mather delved more deeply intowhat the NGST should be able to ac-complish. As mentioned earlier, NGSTwill study the dark period when galaxiesand their constituent stars first formed.It will also attempt to determine the"shape" of the Universe by measuringthe curvature of space, which requiresthe determination of distances to ex-tremely remote objects using, for ex-ample, supernovae as standard candles.Late stages of stellar evolution will bestudied, as well as early stages near thebottom of the main sequence, wherelow-mass objects sometimes becomestars and sometimes end up as browndwarfs, depending on their masses.Closer to home, the NGST will attemptto directly observe objects in the KuiperBelt, which is a zone between the orbitsof Uranus and Neptune that is thought tobe the origin of certain classes of com-ets.

Another important objective is toextend NGST's sensitivity far enoughinto the infrared (IR) to detect emissionfrom objects at room temperature. Thisis approximately 300 kelvins (K), forwhich the emission peaks at 10000 na-nometers (nm), as compared with stellartemperatures of 3000 K (peaking at 700nm) for red (M-type) stars to ooסס3 K(200 nm) for very hot (O-type) bluestars. The detection of such cool objectsis tricky, however, because everythingin the detecting structure must be keptcold enough so as to not emit IR radia-tion itself. Of course, such techniqueshave been developed for missions suchas NASA's Infrared Astronomical Sat-ellite (IRAS) and the currently operat-ing ESA Infrared Space Observatory(ISO), so there shouldn't be major prob-lems in that area.

Dr. Mather explained more aboutwhy we want to build the NGST. First ofall, why do we need a larger telescope inspace, where the cost is so much higher?As we've seen by comparing imagesfrom the HST with what we have tradi-tionally been able to do from the groundusing much larger telescopes, there aremany problems with observing through

the atmosphere. Even though adaptiveoptics techniques are greatly improvingatmospheric "seeing" problems, thesituation is still far superior in space,where resolution is limited only by theoptical quality of the telescope and dif-fraction effects. At longer wavelengths,atmospheric effects are somewhat re-duced on the ground, but emission byhydroxyl radicals, atmospheric water,and other constituents, either severelylimits or entirely blocks extraterrestrialradiation. Clearly, a space-borne instru-ment is not constrained by all theseproblems, plus it is easy to keep thestructure cold by merely shielding itfrom direct sunlight.

Among the important scientificquestions to be studied by the NGST ishow galaxies form and evolve. Dr.Mather showed the classic tuning forkdiagram that Hubble devised in his at-tempt to classify galaxies. This showsthe various types of spirals, as classifiedby the tightness, numbers of arms, andthe presence or absence of a "bar" alongthe major axis. It also shows differentkinds of ellipticals from the essentiallyround to the very oblong. We oncethought that spirals somehow naturallyevolved to ellipticals, because the latterseemed to contain less dust and olderstars. Our picture of this process haschanged dramatically over the last 20years with the realization that galacticmerger events are rather common. Asdiscussed by Dr. Fran~ois Schweizer atthe February 5, 1994 NCA meeting,merger events not only produce many ofthe irregularly shaped and peculiar gal-axy forms, but may also produce ellipti-cal galaxies as their end products. Weshould be able to learn about the forma-tion of galaxies if we can look back farenough to see their initial formation.The Hubble deep field image showsgalaxies having redshifts up to about 5,which is not nearly back far enough(look-back time 5 Ga) to reach the for-mation era. NGST should be able to seeto a redshift of 10-13, corresponding tolook-back times of 11-12 Ga. The ob-servation of objects with such large red-shifts is, of course, a major reason thatthe NGST must be sensitive in the near-IR region where the HST becomes lesssensitive.

Another important topic to be stud-ied by the NGST is the early stages of

star formation. HST images of starforming regions like the ones in Orionshow what appears to be gas flowaround small opaque objects (globules)inside which stars may be forming. It ishoped that the NGST, with its IR sensi-tivity, will be able to penetrate many ofthese clouds to reveal the protostars in-side. Images of the Horsehead Nebularegion in the visible and IR show clearlythat the latter do penetrate the cloud toshow internal activity.

As these protostars age, they de-velop disks of dust that we think eventu-ally condense into planetary bodies.HST images shown by Dr. Mather re-veal such disks around stars like ~Pictoris. The amount of material in thissystem indicates that protoplanetarycollisions have occurred. (We heard alot about the ~ Pictoris phenomenonfrom Dr. Carol Grady at our November2, 1994 NCA meeting.) NGST shouldallow us to see closer to these stars andto perhaps reveal additional detailsabout the nature of their debris. Dr.Mather showed quite a few HST imagesof protostellar disks in Orion and ofregions of star formation in other nebu-lae.

Dr. Mather next turned his attentionto the dark matter problem mentionedearlier. He showed an image of a distantcluster of galaxies in which gravitation-ally lensed arcs of more distant galaxiescan be seen. Since the degree oflensingdepends on the total mass of the lensing"object", in this case the foregroundcluster of galaxies, the total mass can beestimated. An estimate of the mass ofthe luminous matter can be made byclassifying each galaxy in the cluster,assigning a typical mass for that type ofgalaxy, then summing over all galaxies.

Although these estimates may be abit rough, a comparison of the twomasses gives one result that leads us tobelieve that the ratio of dark to luminousmatteris roughly 10 to 1. Essentially thesame results are found from the rotationcurves of individual galaxies. Whilerotation curves have only been deter-mined for relatively nearby galaxies todate, the NGST should be able to extendthis work to much greater distances.

NGST RequirementsThe decision to build the NGST resultedfrom recommendations made by a com-

mittee formed by NASA several yearsago to study the various options forfuture space astronomy missions. Thiscommittee, consisting mostly of nonNASA scientists, made a three-part rec-ommendation: (1) Continue to operatethe HST as an ultraviolet-and visible-wavelength facility; (2) develop capa-bilities for space interferometry, whichuses multiple telescopes to constructimages having resolutions comparableto a single instrument of size equal to theseparation of the interferometer, and;(3) develop a successor to the HST thatis IR-sensitive and considerably largerin aperture. As a result of recommenda-tion 3, NASA Headquarters invitedGSFC in October of 1995 to proposehow this might be done and subse-quently provided some funding to carryout a feasibility study resulting in spe-cific recommendations. The detectorsystem should be sensitive in the IR tosee through dust and to observe the mostdistant galaxies. The extremely highoptical quality originally specified forthe HST is not required in the IR if weoptimize for observations at 2 microme-ters (urn), and this results in substantialcost savings. The telescope aperturewas initially to be at least 4 meters, asdetermined primarily by weight consid-erations and launch capabilities. How-ever, subsequent calculations showedthat at least 8 meters would be requiredto do the desired science, so new waysmust be developed to place the NGSTinto orbit.

In addition to the launch problem,consideration of where to place theNGST is important. Although the HSTis in low Earth orbit, which makes peri-odic visits possible, there are manyproblems associated with a 90-minuteorbit, such as Earth eclipses, orbit de-generation, the difficulty of makinglonger observations, etc. For these rea-sons, it is recommended that the NGSTbe put into a more distant location. Onepossibility is, of course, a geosynchro-nous orbit, but there are several others.An excellent possibility is the L2Lagrangian point, which is locatedabout 1.5 million kilometers outwardfrom Earth away from the Sun. Thispoint is actually easier to reach than thegeosynchronous orbit. Another possi-bility is to launch away from Earth andlet the satellite slowly move into a solar

orbit at the same distance, but perhaps60 degrees or so behind the Earth. Amore ambitious possibility is to placethe NGST farther away from the Sun,perhaps outside the asteroid belt, maybeeven outside the plane of the Solar Sys-tem to escape from most of the inter-planetary dust that interferes with obser-vations, especially in the IR.

Possible DesignsKeeping the telescope cold in space isnot a serious problem because it is onlynecessary to shield it from the Sun witha sun shade. We then saw illustrations ofseveral telescope and sunshade designs.The most important factor is probably tofind a way to make an 8-meter telescopeobjective light enough to launch with alow-cost rocket, which is necessary tokeep the mission cost under control.The rather flexible tolerances in the mir-ror figure make it possible to use noveltechniques to make a thin mirror, andUniversity of Arizona mirror expertRoger Angel has already made a thinmirror of sufficient accuracy. The thinglass is supported by a large number ofadjusting screws that are controlled bypicomotors, which are devices con-trolled by piezoelectric drivers. The realtrick is to build such a mirror in piecesand assemble it in space to reproduce therequired figure. It is assumed that thou-sands of adjustments would be neces-sary, so those capabilities must be builtinto the system. Obviously, there aremany problems to be worked out, butwith the technology improvementsbound to occur over the next decade,along with recent advances in telescopeand instrument making, it should bepossible to construct the necessaryequipment.

Current plans for the instrumentcluster include four detector systems.The central instrument is an infraredcamera with a 2 arcminute field of view.A longer wavelength camera and three-dimensional spectrometer capable oftaking spectra of hundreds of galaxiessimultaneously would be locatedaround the perimeter of the focal plane.

NGSTVs.HSTDr. Mather ended his talk by comparingideas for the NGST with what was done

TELESCOPE, Continued/rom page 5

for the HST about 25 years earlier. Thenew observatory will be larger but con-siderably lighter (about one quarter theweight). Adjustable optics will be used,which should avoid the kind of disasterthat took place with the HST primarymirror. The greater distance from Earthmeans that longer observations will bepossible with simple techniques, al-though the observatory will not be ser-viceable except remotely. All the tech-

niques needed for the construction of theNGST are not yet fully developed, butwe have learned many things along theway and believe that the project is tech-nologically feasible.

There is little doubt that, with thecapabilities described for the NGST byDr. Mather, we would learn a lot aboutsome of the most perplexing outstand-ing problems in astronomy and astro-physics. Along with the other missionsplanned for the first few decades of the

next century, there should be much ex-citement and gratification for those of uswho crave more understanding of theUniverse in which we live.

The NCA is indebted to JohnMather for giving this fascinating in-sight into what we can expect fromspace astronomy over the next few de-cades. I thank John for reviewing this"review" prior to publication. 0

Naked-eye Occultation Saturday Evening, Dec. 6th; Other Northeast U.S. Events

by David Dunham

If it is clear early Saturday evening,December 6th, bring a camcorder orbinoculars to the NCA meeting. Justbefore it begins, at 7:29 pm, the 3.7-magnitude red star A. Aquarii will disap-pear behind the dark edge of the firstquarter Moon, which will be 39 degreesabove the southwestern horizon.Weather permitting, we will observe theoccultation from the parking lot north-west of the Building 10 entrance. Ifconditions are good, the event mighteven be seen without opticaillid. Bmbinoculars are recommended for a goodview. We will have a WWV time signalreceiver. Recording that and the occul-tation with a camcorder can time theevent to 0.03 second, which defines thestar's position relative to the Moon'slimb to about 30 meters accuracy, betterthan the Clementine spacecraft lunarlaser altimeter measurements. Theseobservations are valuable for definingthe lunar profile, information needed toproperly analyze solar eclipse observa-tions to determine climatically signifi-cant solar radius variations. Even if youcan't come to the meeting, whereveryou are, it would be valuable if you cantake a few moments to step outside andtape the occultation with a camcorder.See pages 94 and 96 of the July issue ofSky and Telescope for accurately timing

Roving and RevolvingOver the Red Planet

The review for the November meet-ing was not available at press time.It will be published in the next News-letter.

the occultation with a carncorder even ifyou don't have a WWV receiver. Butwe will use CNN Headline News ratherthan The Weather Channel for the TVtime reference station. If you have nei-ther WWV nor cable, call the U.S. NavalObservatory master clock at 900-410-8463; the call should be placed viaAT&T to ensure use ofland lines, whichwill give an accuracy of a couple ofhundredths of a second. If the call is notmade via AT&T, orifthe National Bu-reau of Standards' WWV- 303-area-code number is used, the call might (ormight not, you would not know) berouted through a geosynchronous satel-lite, causing a quarter-second delay,which is unacceptable. In the Washing-ton, DC area, the USNO master clockcan be reached with a local call to 202/762-1401, but those outside of the DCtoll-free area should not use that num-ber, because it might go through a satel-lite. Record the time just before andafter the occultation (maybe even dur-ing it with a portable phone). Nextweek, a view of the Moon showingwhere A. Aquarii will disappear at sev-eral North American cities will beplaced on our Web site given at the endof this notice, but it is not needed toobserve the event. The star is so brightthat, even with a telescope, a low powercan be used so that the whole dark sideof the Moon can be viewed, and the starsimply followed up to the edge of theMoon to the disappearance. More use-ful on the Web site is a list of the pre-dicted Universal Times for about 200North American cities.

There are several other occultationsthat can be taped with a camcorder

pointed into the eyepiece of a telescope;predictions for them are given below.The events marked with * can probablybe recorded directly with a camcorderwithout a telescope, if your camcorder is12x or higher, but the Aldebaran disap-pearance will be hard without a scopesince the bright part of the nearly fullMoon will be very close. The eventsmarked with? might be recorded di-rectly if conditions are good. Whenaiming a camcorder into an eyepiece forevents relatively farfromthe sunlit partof the Moon, first focus on the sunlit partof the Moon with autofocus, then switchto manual focus as you move the viewtowards the star. The Hyades disappear-ances that precede Aldebaran's disap-pearance on Friday evening, Dec. 12,will be easy just using autofocus sincethose events will all occur close to theterminator, providing a good referencefor the autofocus. See IOTA's Webpage at http://www.sky.net/-robinson/iotandx.htm for more information. Thepredictions on the next page were com-puted for Greenbelt, Maryland, about 12miles northeast of downtown Washing-ton, DC, but the times will usually begood to within a minute within 40 milesof Greenbelt, with the occultation usu-ally occurring earlier in the western sub-urbs. For more accuracy or more distantlocations, the A and B factors can beused, as described in the explanation ofthe predictions given at the end. Also,predictions for other locations will besupplied upon request bye-mail atdunham@erols.com for observers whowill try to time many ofthese events. 0

1.0.T.A.Total Occultation Predictions For 1997 December for Greenbelt, Maryland,Longitude W 76d 52' 09.9", Latitude +38d 59' 10.1", Height +53 meters

DAY E.S.T.H M S

6 19 29 296 20 45 227 20 17 2610 17 41 5812 19 55 2912 20 04 1212 21 00 0312 21 15 1412 22 59 5713 00 16 3813 01 26 2619 04 59 4620 06 18 1821 00 26 5122 00 57 1624 02 49 3226 04 49 32

P Z.C.NO.

D* 3353D 3360D 3505D 368D 667D 672D 677D 680D 685D* 692R 692R 1486R 1589R 1678R? 1772R 1994R* 2223

VIS SPMAG3.7 MO6.3 KO5.6 KO6.3 KO5.3 G56.6 F84.8 A56.7 F26.5 FO0.8 K50.8 K54.6 K25.7 M25.8 F53.9 AO6.5 F84.0 KO

PCTSNLT47+48+59+88+98+99+99+99+99+99+99+73-64-56-47-28-12-

SNAL

MNAL3930433442445456676454605311667

MNAZ21023(l2121061041061191241722152411982119596106115

CUSPANG59S88S60N30S77N52S35S16S15S37S-84S43N90NlIS46S41N83N

122936114657107124144143120241317269190225320283

AM/O-2.1-1.2-1.1-1.8-D.7-1.4-2.1-2.7-2.7-2.1-1.7-1.0-1.9-D.4-D.3+0.1-D.4

B StarMfO Name-1.0 A. Aquarii-D.3 78 Aquarii+ 1.3 20 Piscium-D.3+2.3 75 Tauri+0.8-D.2-2.0-3.0-1.5 Aldebaran+0.8 Aldebaran-3.3 31 Leonis-1.4 56 Leonis+7.4 89 Leonis+2.3 £ Virginis-1.6+0.4 Y Librae

The columns in the IOTA table above are defined as follows: DAY E.S. T. (H M S) gives day of month and hours, minutes, secondsof the predicted Eastern Standard Time of the occultation event. P is phenomenon: D for disappearance, R for reappearance. Z.C.NO. is the star's number in Robertson's Zodiacal Catalog. VIS MAG is the visual magnitude of the star. SP is the spectral typeof the star. PCT SNLT is the percent ofthe Moon's disk sunlit (100% = Full Moon), followed by + for waxing, - for waning.SN AL is the altitude of the Sun above tile horizon, given only when it is greater than or equal to -12. All angles are in degrees.MN AL is the altitude ofthe Moon above the horizon. MN AZ is the azimuth of the Moon, measured along the horizon eastwardfrom the north point. CUSP ANG is the cusp angle of the event. This is the angle from the nearest lunar cusp to the star. The nearestcusp is identified by letter as the north (N) or south (S) cusp. Cusp angle is positive on the dark limb and negative on the brightlimb. W A is theW atts angle of the event, measured at the center of the Moon's disk from the Moon's north rotation pole eastwardto the star. It can be used with a lunar map to estimate the point of reappearance of a star relative to lunar features; a W.A. of 270is near the lunar equator, 180 is near the south pole, and 360 is near the north pole. Events near WA 290 are conveniently closeto Mare Crisium. A B (M/O M/O) are the rates of change of the predicted occultation time with changes in the observer's longitudeand latitude, respectively. The units are minutes of time per degree of west longitude or north latitude (M/O).

Dec2Dec5

Dec IDec 3Dec4Decl4Dec27

TueFri

17:12 ZC277318:17 ZC 3211

6.0 8+8.0 35+

-IS4S

Myersville, MD (S-5) & Logansvil.,PA, -6Olney, Clarksv., & BelAir, MD (Sun-17dg)

PPM 183823 9.4SAO 189113 9.0SAO 134036 6.0PPM 195501 9.544 Eridani 5.5

NeoptolemusHerculinaArtemisHildaNipponia

dmag duros

7.9 82.8 67.1 II4.8 77.5 4

MonWedThuSunSat

19:4117:587:065:031:45

Virginiae. CarolinasWisconsinMexicoGeorgia

Phone the IOTA occultation line, 301-474-4945, for updates and details; also, meeting places and maps for grazing occultationsare often given on IOTA's Web site at http://www.sky.net/-robinson/iotandx.htm

National Capital Area Astronomical EventsFree Lectures at the Einstein Planetarium and Other Daily Events

National Air & Space Museum

202/357-1550,202/357-1686, or 202/357-1505 (TTY)Home page: http://www.nasm.edu

Other Planetariums,Observatories, and Science

Centers in the Area

Montgomery College Plan-etarium -"Day of the Sun's Re-turn, the Winter Solstice" TakomaPark, MD. December 20. (See theirweb site at http://myhouse.comlmc/planet.htm.)

Campus Observatory OpenHouse - "Magnetic Storms on theEarth and Other Planets", speaker:Dennis Papadopoulos. Departmentof Astronomy, University of Mary-land, College Park, MD. December5, 8:00PM.

"Topic to be announced.", speaker:Dr. Pat Harrington. Department ofAstronomy, University of Mary-land, College Park, MD. December20, 8:00PM.

National Museum of Natural His-tory -"After the Planets Formed",speaker: Mereoriticist Dr. TimothyMcCoy describes the process that

Meteor Showers for December

Puppids-Velids Nov 27-January(Max: Dec. 9 &Dec. 26)

Dec 7-16(Max: Dec 13)

Dec 17-25(Max: Dec 23)

Meteor web sites to explore:www.ticetboo.demon.co.uk/meteors.htm which includes a link to asite on anomalous meteor phenomena,

shaped asteroids and planets trans-forming them from rocks to worlds.December 5, 12Noon. Baird Audi-torium, Free to the public.

National Air and Space Museum-"Together in Space", speaker:Rob Landis from Goddard SpaceFlight Center will present a histori-cal overview of the Soviet spaceprogam and preview the programsbeing planned as joint ventures be-tween the U.S. and Russia. Decem-ber 27, 6:00 PM, Einstein Plan-etarium.

Mount Rainier Nature & Recre-ation Center - "Winter Stars"Historic Bladensburg WaterfrontVisitors Center, 460 I.AnnapolisRd,Bladensburg, MD. Due to construc-tion, activities at the WaterfrontCenter maybe moved to an alternatesite. Call Jean Tierney at 301/627-6074 for information. December 5,6:30-8:00 PM.

Check your local web sites for anyother events that may be happeningin the area.

www. maa. mh n. de/Comet!calendar.html. Also referenced is GaryW. Kronk, author of the book MeteorShowers: A Descriptive Catalog (1988)

Cosmos RevisitedDecember

Life as a PlanetaryPhenomenonBy Andrew Knoll

Lectures begin at 6:00 PM at the Na-tional Air and Space Museum. For moreinformation, call Missy Snelling at 202/357-4260.

"A GlobalPerspective onGalactic Evolution"By Michael Fall(STSI)

"Implications ofMeteoritic PresolarGrains for GalacticEvolution"by Conel Alexander(DTMlCIW)

Seminars are held on Wednesdays at11;OOa,m. in·theSemiftaf;,~Main (old) Building. Coffee and teawill be served at 10:45 a.m. Please callto confirm that there have been no can-cellations. DTM is located on 32ndStreet, one block south of its intersec-tion with Military Road. Proceed southon 32nd Street, one block to JocelynStreet, turn left on Jocelyn and right intothe parking lot. CIW, 2021686-4370(Extension 4378 or 4383)

who is in the process of placing his bookon line. He also keeps a calendar andwrote a historical piece on "Meteorsand the Native Americans."

Newsletter Deadline forJanuary Star Dust, December 15, 1997

Send Submissions to Alisa & Gary Joaquin, at 4910 Schuyler Dr, Annandale,VA,22oo3-5144. Leave a message on voice mail703nSD-1636. Text files orgraphic files in .GIF or .TIFF may be sent via E-Mail to ajglj@erols.com or faxsubmissions to 703/658-2233. No submissions will be accepted after the20th. There will be no exceptions. We need a reasonable amount of time todesign, edit, and review this newsletter. The Holidays are upon us and we wouldappreciate everyone's help in this matter by getting everything in on time. Wewill be going to Nebraska and we will need to get this mailed before December23. Thank you.

National Capital Astronomers, Inc.SERVING SCIENCE & SOCIETY SINCE 1937 Consumer Clinics on selection, use, and care of binoculars andNCA is a non-profit, membership supported, volunteer run, public- telescopes, provide myth-breaking information, guidance, andservice corporation dedicated to advancing space technology, demonstrations for those contemplating acquiring their firstastronomy, and related sciences through information, participa- astronomical instrument.tion, and inspiration, via research, lectures, presentations, publica- Dark-Sky Protection Efforts educate society at large about thetions, expeditions, tours, public interpretation, and education. serious environmental threat of light pollution, plus seek waysNCA is the astronomy affiliate of the Washington Academy of and means of light pollution avoidance and abatement. NCASciences. All are welcome to join NCA. For information: is an organizational member of the International Dark-Sky703/841-4765. Association (IDA), and the National Capital region's IDA

representative.Classes teach about subjects ranging from basic astronomy to

hand-making a fine astronomical telescope. NCA's instruc-tors also train educators in how to better teach astronomy andrelated subjects.

Tours travel to dark-sky sites, observatories, laboratories, muse-ums, and other points of interest around the National Capitalregion, the Nation, and the World.

Discounts are available to members on many publications, prod-ucts, and services, including Sky & Telescope magazine.

Public Sky Viewing Programs are offered jointly with theNational Park Service, the Smithsonian Institution, the U.S.Naval Observatory, and others.

NCA Juniors Program fosters children's and young adults'interest in space technology, astronomy, and related sciencesthrough discounted memberships, mentorship from dedicatedmembers, and NCA's annual Science Fair Awards.

Fine Quality Telescopes up to 36-cm (l4-inch) aperture areavailable free for member's use. NCA also has access toseveral relatively dark-sky sites in Maryland, Virginia, andWest Virgir,.ia.

SERVICES & ACTIVITIES:Monthly Meetings feature presentations of current work by re-

searchers at the horizons of their fields. All are welcome; thereis no charge. See monthly Star Dust for time and location.

NCA Volunteers serve as skilled observers frequently deployingto many parts of the National Capital region, and beyond, oncampaigns and expeditions collecting vital scientific data forastronomy and related sciences. They also serve locally byassisting with scientific conferences, judging science fairs, andinterpreting astronomy and related subjects during public pro-grams.

Discussion Groups exchange information, ideas, and questions onpreselected topics, moderated by an NCA member or guestexpert.

Publications received by members include the monthly newsletterof NCA, Star Dust, and an optional discount subscription to Sky& Telescope magazine.

NCA Information Service answers a wide variety of inquiries_ .••..'" about space technology, astronomy, and related subjects from

the public, the media, and other orgar.izattons.

Enclosed is my payment for the following membership category:[ ] Regular

[ ] Sky & Telescope and Star Dust. ($54 per year)[ ] Star Dust only ($27 per year)

[ ] Junior (Only open to those under age 18) Date of birth: _Junior members pay a reduced rate.[ ] Sky & Telescope and Star Dust. ($42 per year)[ ] Star Dust only ($15 per year)

---------- ------ ------------- (--) ------First name Middle Last name Telephone

If family membership, list names of additional participating immediate family members in same household, with birthdates of allthose under 18 years old: _Note: If you already subscribe to Sky & Telescope, please attach a recent mailing label. You may renew this subscriptionthrough NCA for $27 when it expires.Make check payable to: National Capital Astronomers, Inc., and send with this form to:NCA c/o Jeffrey B. Norman, 5410 Connecticut Avenue, NW, Apt. #717, Washington, D.C. 20015-2837.The following information is optional. Please indicate briefly any special interests, skills, education, experience, or otherresources which you might contribute to NCA. Thank you, and welcome to NCA!

Getting to the NCA Monthly MeetingMetrorail Riders - From Medical Center Metro Station:Walk down the hill, pass the bus stops and turn right at theanchor onto Center Drive. Continue uphill to Building 10,the tallest building on campus (walking time about 10minutes). Also, the 12 bus line connects the Bethesda (7: 16PM) and NIH (7:23 PM) Metro stops with Building 10 (7:25PM).

To North China Resaurant- Take Wisconsin Avenuetoward Bethesda and head right onto Woodmont FollowWoodmont to Old Georgetown Road and make a right. Theresaurant is a few blocks on the left (7814 Old GeorgetwonRoad). Alternately, turn right on Cordell from Woodmontand proceed a few blocks to Old Georgetown Rd., where youwill come out right near the restaurant. Park around corner.

Star DII$lispublished ten times yearly (SeptembertllroughJune) by the National Capital Astronomers, Inc. (NCA), anonprofit, astronomical organization serving the entireNational Capital region, and beyond. NCA is the as-tronomy affiliate of the Washington Academy of Sciencesand the National Capital region's representative of theInternational Dark-Sky Association. NCA's PhoneNum-ber 03}841-4765. President: Harold Williams, 301/565-37()9••Deadline for Stllr Dllst is the 15th of the precedingmonth. Editors: Alisa & Gary Joaquin, 4910 SchuylerDr., Annandale, VA 22003, 703{750-1636,E-mail: ajglj@erols.com ••Editoral Advisor: Nancy ByrdStar Dllst © 1997 maybe reproduced with credit toNational Capital Astronomers, Inc.

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900 Rockville Pike (Wisconsin Ave.)Parking ci

i ~

Building 10Clinical Center(Meeting)

Enter Building 10 from North(Main Entrance); passing throughthe double doors. Turn left andfollow signs for LippseltAuditorium. If unsure, ask fordirections at the InformationBooth inside Main Entrance.

National Capital Astronomers, Inc.If Undeliverable, Return toNCA c/o Leith Holloway, Apt. #M-lO10500 Rockville PikeRockville, MD 20852-3331

MEDICAL CENTERMETRO RAIL STOP

(REDUNE)

FIRST CLASS

7/98Leith Holloway Apt MIO10500 Rockville PikeRockville MD 20852-3331