2:AI RA.NEWSLETTER
Vhen these two methods are applied rc galaxies, we often lnside.,, find that the mass determined by the second method is Looking Up 3 several times as large as the visible mass determined by the Acknowledgement of ZOO0 Donors 4 first. Dynamical studies sugges t that this extra mass is not in Summer Sky 6 the disk of the galaxy where we find the bright stars and the gas and the dust, but is widely distributed in the surrounding halo, where we fin d relatively few stars. Srrpposing that it is always true that most of the matter in the halo is dark, then the halo of a galaxy like the Sombrero, where there are many This feature is inspired by the questions we baae receioed over the years fro* interested stars, should be exceedingly massive. \7e were therefore readers. If yow haoe a question'about an surprised to find that the total mass of the halo of the astronornical topic, please forward it to ws. Sombrero was quite ayerage. It must be that somethitg has happened in the halo which has caused the formation of an exceptionally large number of stars. This does not mean that Robert Hoyle asks: there is no dark matter. \We have seen only that the total mass Dear Dr. Shane: Your articles on the Sky in the Newsletter is quite normal but that a larger than normal fraction of this are always very interesting and particularly thought mass is in the form of halo stars. tMith regard to the total provokirg. I was intrigued by the fact that Mt04 is not dynamical mass, the number that we get is 0.6 trillion solar "does surrounded by an inordinate amount of mass that masses inside a 20 kiloparsec radius although what happens not seem to produce any observable radiation" (presum ably outside this radius is anybody's guess. The number which dark matter). If the rotational velocity component is used you quote (1.3 trillion) is somewhat larger, although not to determine galactic mass does this mean that such unreasonable provided it is a measure of the total, not just the calculated mass does not have any dark matter in it? If visible mass. In all these calculations the distance remains an there is dark matter inside the radius, how can we deter- important source of uncert arnty. mine the number of stars in a galaxy? The most interesting part of our discussion is now quite an Dr. \flhitney Shane responds: old story. By looking at the spiral structure, we were able to Thank you for your thoughtful questions. To answer your estimate how much of the mass was concentrated in the disk questions, let me startby describirg the two methods of of the galaxy. The material in the disk moves under influence mass determination that we may use in cases such as the of the whole mass of the gaIax,y, includirg the halo. But the \We one I was discussirg. can measure the luminosity of the tendency of the matter to con centrate in spiral arms is galaxy using a photometer and, supposing we know its governed by the self-gravity of the matter in the disk itself. distance, which is always uncertain, we can convert this to Vith the help of some rather complicated mathematics, we absolute units, such as units of the luminosity of the Sun. can show that the tilt of the spiral arms (or their separation, If all stars were similar to the Sun, then this number would which we were able to measure) is related to the amount of also be the total mass of the stars. Actually, the average star mass in the disk. \(e found that about20 per cent of the total in a galaxy like the Sombrero is less bright, for its mass, mass of the galaxy is located in the disk. This leads to the than is the Sun. So we have to multiply the total luminos- rather unexciting result that the Sombrero is really a very ttyby some factor, usually 3 or more, dependirg upon the aloerage sort of disk embedded in an ayerage sort of halo. The kind of stars which appe ar to be present, in order to only exceptional part is the large number of stars in the halo, estimate the total *r* of all of the stars. If we want to and it is this that makes it such a strikirg object. include all of the visible material, we must add somethirg to account for the gas and dust, which we can see as the dark band across the face of the galaxy but this is generally Thanks to our Generous Donors! a correction of only a few per cent. The second method of In March ZOO1, MIRA received a $1,000 grant from the mass determination is to measure the rotational velocity. Yellow Brick Road Benefit Shop which will aid in the This is particularly easy when the gal axy is seen edge on installation of MIRA - Exploring the Universe from the because there is no proiection factor to worry about. This Central Coast which will be re-hung at the Hamming As- measures the mass interior to a sphere whose radius is tronomy Center. The exhibit was previously shown at the determined by the point at which the measurement is Pacific Grove Natural History Museum. made. If the matter is not spheric ally distributed, then received there is a small correction, but this can be dealt with. This Also was a $2,500 donation from The Catherine L. will include all of the mass, because all of the mass contrib- and Robert O. McMahan Foundation for the cost of a low- utes to the gravity, whether it be in the form of stars, of gas resolution area spectrograph. and dust, or in some other form which we have not yet The Pebble Beach Company generously donated $1,500 identified but which we caII, for lack of a better name, toward the installation of MIRA - Exploring the Universe fro* " dark matter." the Central Coast. UMMER 20A1:3 Looki ng Up Calendar of Events Dr. witb Arthur Babcock Free Observatory Tours at OOS! Marvel at MIRA s 36-inch Red Sky in Garmel Valley professional research telescope! The Oliver Observirg Station is located on Tas sajara Road in on Friday evening, March 30, I received a phone call from Carmel Valley, in the Los Padres Kim Cohan telling me that a friend of his from Carmel National Forest. Valley had called him to ask -hy the night sky looked red. As it turned out, this was a rare instance of the aur ora Reservations are required. being visible this far south. Indeed, that night there were 5 Arg - Observatory Tour reports from across the southern U.S., and even from as far south as Mexico, of red and green glows in the night 2 Sept - Observ atory Tour sky. Fall Lecture: Dr. Alex Filippenko will speak on Einstein's Vhile the aurora borealis is often visible from nothern Biggest Blunder? The Case for Cosmic 'Antigraviq." locations, it takes a violent solar evenr to produce aurora MPC Room 103, 7 p.m. November 10th. effects visible from the mid latitudes, and this occasion was due to a coronal mass ejection from the largest The Bonestell Memorial Lecture: Dr. Frank Shu, the sunspot in a decade (see illustration). NASA s ACE preeminent theorist on the formation of our Solar System, will discuss the formation (Advanced Composition Explorer) spacec raft detected a process of the sun & planets. shock wave in the solar wind, which arrived in Earth's '$[inter Lecture: Dr. Imke de Pater will show the Universe atmosphere about 30 minutes Later. through the eyes of telescopes using the latest techniques in Vhen Kim's phone call alerted me ro go ourside and look adaptive optics. up, I saw a faint, diffuse red glow from the northwest Lectwre dates to be announced. horizon to the zenith. The effect was subtle, but I was sure it was real. Lateg I saw a number of photographs All lectures, star parties, and tours are free and open to the taken that night from the southern U.S. and they all public. Call the MIRA office at (831) 883-looo or email showe d a fairly uniform red glow. The glow is emission [email protected] for more information. from tonrzed oxygen and nitrogen in the atmosphere.
The next day,I called FoM member Robin Cas ady about this event, and he responded with this excellent image of the monster sunspo t that caused this unusual event.
VOLUNTEE,RS STANTED!
MIRA has several interesting projects that we will be The largest sunspot in years; the round black spor indicates working on in the coming year - please phone the offi ce at the size of the Earrh. Image by Robin Cas ady, using a 883-1000 or email us at [email protected] and let us know of 130mm Astro-Physics refractor at f/1,6.6 and an Astrovid your talents and interests! 2000 video camera. 4 :AI R.tr.NEWSLETTER
The Monterey Institute fo, Researcb in Astronomy gratefully acknowledges gifts and membersbips fo, 2000 from indiaidwals, families, corporations, and foundations. 2000 Associates Circle 2000 Sponsors ($1,000 and oaer) ($1oo - $24e) I sc Adelman ,NIvarez Edward Leibhardt Kenneth Gabrielle Janet I I Arthur & Barb ara Babcock Michael Anderson Tom Logan 1 Cratg & Lynn Chester Richard Baum gartner Mayflower Hotel Margaret L. McCrary City of Pacific Grove &. Ehzabeth Salzer Mclntosh Mrs. Rockwell Hereford Bill Bishop James CoI. Nathaniel Mewhinney William R. Hewlett 8r Lorene Hall Mid Valley Shopping Center'!' Ansley Hill Robin Casady 'r (Porter, Clemens, & Craft families) Herbert Hoover III Dr. & Mrs. Robert G. Chapman Harriet Mittledorf Monte rey Peninsula Volunteer Mr. 6c Mrs. Craig Cholar Services Christopher Mooers Ralph Carmichael \Thitney 8. Clasina Shane George Nicolayev Donald s( Robbin Close \Vm. Bruce and Sandra \(eaver Susan Sc Bill Phillips Kim 8r Laura Cohan Post Ranch Inn \Tarren Yogi Max & Annie Cornell Quail Lodge 2000 Patrons Betty Curry ($soo - $etts Ruth Rich Mrs. Justin Dart Monte rey Insurance Agencies Mr. 8r Mrs. Charles Shane Dale Ditsler Remote Telescope Comp any Franklin Smyth er Daniel 6c Nina Dobkin F.A. \(eit J. Patrick \Taddell William 8c Nancy Doolittle 2000 Sustaining Fred Terman ($z;o William Drake - $401 Roc Trout Randall Sc Evelyn Enger James Carroll, Sr. Cristina Veaver & Eric Ullian Stanley Duke Bill & Peri Frantz \Wang Joseph & Jamie Ted April Gamble Christopher Fulton & \flashington Middle School Band Konny Gloy Star Gerawan Boosters Roy Dean Hardy Richard D. Hamilton Kai Voehler Dennis & Susan Mar \(anda L. Hamming Yanagisawa Family Living Trust Charles Anne Oostdyk 1 & Roy D. Hardy Marsha McM ahan Zelus i Allyn Saroyan Thomas Haven Ralph Meeker and Deborah Smith Dr. G^ry Holzhausen
Mrs. Hulet Smith Tom and Devin Kehl Mr. & Mrs. Dean Storkan John Lane Sunburst Farms SUMMER 2001:5 2000 Family Memberships 2000 Members ($so - $t1 ("p to $4e) F.L. Allard John Kochis Rod Allison Robert Jones 8c DonnaZahn Christopher Angelos Kathryn Loftus Lee & Macia Keely Roger Born Susan Lowell Gene Barnes Dr. & Mrs. \Tilliam Keller Laura Brisby Mrs. Ralph I. Meeker L. Barnes Dr. & Mrs. Robert Kellogg Joan G^ryBryant Mr. & Mrs. Lee Mellinger Bergez Yvonne Ascher-Laub John Fred Buskirk G. van der Molen Dr. and Mrs. Robert Black Mr. 8c Mrs. Edgar Lehmann David Canright John Mulshine James M. Brown Tom Lougheed Francis Cartier George Niesen G^ry Byrd Martin 6c Carol Lyndon Elizabeth A. Christian Jana O'Brien Mr. & Mrs. Theodore Calhoon Gerald Macke nzie Dr. Anthony Ciavarelli Greg Orsik Mr. 8c Mrs. John Carley Margaret McCrary James R. Clynch Lauretta A. Peevey Jeff 6r Reb ecca Carroll Mr. 8c Mrs. Art McDole Sanford Colburn Thomas Peli can Richard Cassam 8c Michael McMahan Patti Compton Andre Pierce Diane d'Urso Robert Melton Ron Corda Patricia Polk abla Carl Christensen Col. Nathaniel Mewhinney Donald F. Criley Jean Rowell & Jo Ann Novoson Mr. 8c Mrs. Pearson Morse Dr. H.T. Croley David Smith Eugene C. Crittenden Villiam E. Murray, Gene & Martha Crittenden Jr. Raymond H. Cy, Richard Spaulding M/M Antonio Nafarrate G^ry Cutler Jack Davis Hugh Smith Linda Newton Donald ec Noel Dickey Bernard C. Denton Eleano r Taylor Deryck Nuckton Estelle Park Douglas Estelle Park Douglas Mark tueblood Ruth Ny. Ji* Eagle Eugenia B. Dujmovich Dr. Robert E,. Turner 8c Fleidi Pratt Barbara Eastman John Sarah Epperson Hazel \Teaver 8r Barbara Pugh Dr. Viiliam Edson Jack Kathy A. Feather Nancy \Tilson Frederick erB arbara Rainer Oscar B. Jean & James Esary Paul Fenwick \filson Harrison S. Robinson I)r. Villiam H. Falor, Jr. Thelma Fredrickson-Clark Margaret M. \Tishart Villiam & Lewis Rolland Jr, 8c Bob Fisher Patricia Gilda Alma \7ood Lyn & Alan Rosen Sean & Reb ecca Flavin Nina Gordon Arthur Schoenstadt \Talter J. Flemirg Cindy Roberts-Gray Schreiber Robert 8c Dale Forrest Ji* Tory Hall Vic 8c Shayna Selby R.N. Forrest Ruth S. Hartmann Dr. Rex Shudde G^ry Haffner Otto Heinz Tom 8r Sue Sibbald The Hawley Family Steve Hillman Kennerh 8( Sally Sikes Alan Hedgard Kristin Flocevar Peter Simon Dr. Bob Heighton Lloyd Holm Hugh sc Phyllis Steven Stewart \( Elizabeth Hughes Aaron Strefling S. Pil Yim Hobson Florence Jensen Chris \flahle Georgina Houser Mark Jones \Tashington Middle School & Rod Norden Band Boosters R.K. Kalmbach Jo. &. Liz Flouston Edith R. \fliranten Barbara Johnson John 8c SandraZasio Ted Johnston 6 : Ain-A.NEWSLETTER The Summer Sky Dr. Vhitney Shane, MIRlt's Charles Hitchcock Adams Fellow
Fixed Stars North Ameri can nebula there Many of us, when examinirg is just one hot star, HD the night sky, find it difficult to 199579, and it is vefy hot associate the accidental configu- indeed, about as hot as a rations of the stars that make nomal star can get. The gas up the constellations with the density can be estimated figures they traditionally from a study of the spectrum represent. The same is true of of the nebula, and is found to some of the nebulae, whose be quite low, only about 10 common names are only atoms per cubic centimeter remotely suggested by their which will help to explain appearances. Happily the tlre low surface brighiness. North Ameri can Nebula and its Combined with the companion the Pelican Nebula, distance, which is about do not belong to this class. 1000 parsecs, this gives a Both have a rcally remarkable mass estimate of a few resemblance to the objects for thousand solar masses. which they are named.
Although the brightest nebulae seem to be located in the Winter The l{ortb American Nebwla, Milky \[ry (the Orion Nebula NGC TOOO Planets comes to mind), the Summer Milky Vry also offers good, Mercury will be visible in the morning sky in early and somewhat more comfortable, hunting. For an observer July, where it will reach maximum elongation on 9. It will be with a small telescope or binoculars and a dark sky, the July easy to find on when it will be 2 degrees south of North Ameri can Nebula, known officially by the easily Julyl2 Late in the month it will disappear in the morning remembered name of NGC 7000, is a good candid ate. It is Jupiter. twilight and will not be easily observable again until Octo- easily located, lying 3.5 degrees due east of Deneb. It is ber. large, between 1 and 2 degrees in diameter, but quite faint, so it may be hard to identify in this crowded region of Cygnus. During the whole summer quarter Venus will be The Pelican Nebula, which lies about 1.5 degrees to the west, visible in the north-east morning sky, rising 2 or 3 hours is smaller and so faintthat it can be seen only on photo- before the Sun, but it will remain low in the sky graphs. during these early morning hours and is not favorably placed for observation. The visual observer will probably be unable to distinguish he form of the North Ameri can Nebula, but on a photo- Mars will be moving into the evening sky during graph the correspondence with a map of the continent is where it will still be well placed for observation. striking. An observer with a sufficiently vivid imagination Jrrly, It will move lower into the southwestern evening sky as the will no doubt succeed in identifying the brighter stars with quarter urban agglomerations. Even the orientation is correct, with Progresses. Canada to the north and California to the east. (Remember Jupiter will appear in the northeastern morning sky during that when looking upward to the sky the directions are the Jrrly and will become more favorably placed for observation mirror image of what they are when looking downward upon as the quarter progresses. the Earth. Most of you will have no idea how difficult it is Saturn is now more than an hour ahead of and is. to explain this to beginning students!) The Pelican Nebula, Jupiter thus visible in the morning sky during the whole quarrer. located somewhere in the Atlantic Ocean, is about where It starts its retrograde motion on Sep tember 27. one would expect to find the mythical continent of Atlanris, leading to its alternate name, the Atlantis Nebula. LJranus and Neptune will both pass opposition during the quarter, but both will be low in the southern sky and thus Both of these nebulae are of the emission kind, meaning not well placed for observation. that we see radiation from hot gas. This gas must be heated, and ionized,by one or more hot stars, andin the case of the i---- UMMER 2001:7 Meteor Showers Caretaker's Corner A11 of the stronger meteor showers in this quarter will suffer from moonlight. The always reliable Perseids, which - Ivan Eberle will be visible for a few days around Augus 1,2, are best t I am often reminded of the fact that living on Chew's seen in the morning hours when the last quarter moon will Ridge is like living in the fourth world (it might qualify for be a problem. The Southern delta Aquarids on 28 and July the third world except for havirg to truck in the water during the alpha Capricornids on 30 will suffer even more Jrrly the summer). Off the power grid 8c unwired, f've felt like from moonlight. those kids attendirg school by shortwave radio in the Observers who insist upon a dark sky will have to be outback of Austrailia (Editor's note: being off the power content with three yery weak showers, the kappa Cygnids grid has had certain advantages this year). At long last OOS and the Northern iota Aquarids in the middle of August has been elevated from its informationally challenged status. and the poorly studied Piscids in mid September. Two years ago, we bartered a year's worth of time as an excellent radio-repe ater site for the eventual use of three 900 Comets Mhz spread-spectrum wireless modems. It has taken some effort to establish another workable down-link site after the No dramatic comet appe arances are expected as of this successful conclusion of the original project, but I am pleased writing. The short period comet Borrelly should be visible to report that this wireless link is now up and running. The by the beginnirg of the quarter and reach ninth magnitude result is that the OOS has a speedy 1.1.5, 200 Kbps connec- by September as it gradually moves north. The long period tion to the Internet, with no extra recurring monthly charges. comet C/2000 \fM1 will probably become visually observ- The downlink site and ace networking expertise came able during the qu arter, but it is headed for the southern courtesy of indefatigable FOM volunteer Bill Bishop, to hemisphere where it will be when it reaches maximum whom we owe a mjor debt of gratitude. Beyond the greater brightnes s. efficiency for those of us toiling away in the Nether Regions, such connec- Eclipses tivity offers The least exciting news of the quarter is the eclipse calen- other interest- dar, which has one entry a partial eclipse of the Moon on irg J.rly 5 visible only from Australia, Antarcttca, and the possibilites. western Pacific. One is that the link may be utilized for digital remote control of the MIRA 36" telescope.
Indefatigable F OM volwnteer Bill Bishop
Stan Karas, MIRA's steely-eyed obseruatory engineer looks up from his work on tbe 36" telescope.
Artbwr Babcock works with summer intern Jm Yee as thry check the cooled electronic camerd, on the MIRA 36-incb telescope. AI RA. StAff Welcome to New Friends Gordon Jones, Char, Board of I)irectors Dr. S7m. Bruce $7eaver, Director I(ate Colby, Administrator Roger Born Dr. \)Thitney Shane, Charles Hitchcock Adams Fellow Melissa Btocklehurst Dt Ctate Chester, Astronomer P. Croockewit Claas Shane, Llbranan Yilmaz Degprmenci Stan I(aras, Observatory Engineer Marion R. Flahetry Dr. Arthur Babcock & I(ate Colby, Newsletter Co-Editors Lee Frank III Dt. Arthur Babcock, Office Jo. Volunteer Nina M. Gordon* Ivan J. Ebede, OOS Carctaker ,<*>k Sherwood & CynthiaHail, Hall* The Monterey Institute for Research in Astronomy owns and operates Tory the Oliver Observing Station under permit from the United States Roy Dean Hardyx Department of Agriculture-Forest Service. Otto Heinz ,<** Burt Mry The Monterey Institute for Research in Astronomy owns and operates Robert Mclnryre family the Richard Sfl. Flamming Astronomy Centet and the Ralph Knox Shops Gary tr. Melcher through an with the U.S. Department of Education. ^rrangement Simon Yan der Molen Anita H. Muhs HarmMunk Anton Prangex Eleanor G. Taylorx I would like to become a FRIEND OF MIRA and receivel Belinda Lowe-Schmahl Hunter Sfl Stewart* the MIRA Quarterly Newsletter. I Enclosed rs my membership donation of $_ ln addition, I am making a special gift of $ I I *denotes 2500.00 Associates Circle 100.00 Sponsor renewal I 1000.00 Associate 50.00 Family 500.00 Patron 35.00 Member I 250.00 Sustaining 15.00 Student I I MIRA welcomes corporate and business me mbers. Contributions are tax deductible as allowed by law. I NAME I I we are proad to participate i, ffi ADDRESS I
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