THE COMET’S TALE Newsletter of the Comet Section of the British Astronomical Association Volume 7, No 1 (Issue 13), 2000 April A Brief History of Comets II (1950-1993) The following text is adapted considered to be heavenly omens surprising that, continuing the from a major review on Comets, and were not yet clearly earlier investigations by Swings prepared by Michel C. Festou established as celestial and McKellar, most spectroscopic (Observatoire Midi-Pyrenees, (astronomical), rather than studies between 1950 and 1970 Toulouse, France), Hans Rickman meteorological phenomena in the were devoted to a never-ending (Astronomiska Observatoriet, terrestrial atmosphere. Then attempt at discovering and Uppsala, Sweden) and Richard followed two centuries of mostly identifying new emission lines M. West (European Southern positional measurements with and bands, as well as at Observatory, Garching, Germany) emphasis on the motions and the unraveling the structure of the and published in the review orbits, lasting until the early 19th rotational and vibrational bands journal Astronomy & century, when the era of cometary of the comet radicals and ions. A Astrophysics Reviews (A&AR) physics was inaugurated, in special reference must here be (Part I, Vol. 4 pp. 363-447, 1993) particular by the passage of made to the numerous and P/Halley in 1835. The next major important contributions from the This is the second part of a brief step forward occurred in 1950 Liege school, reviews of which historical review, covering the with the sudden emergence of the are given by Swings (1956) and period from 1950 to 1993, i.e. modern picture of comets as Arpigny (1965). During this until just before the crucial years being essentially very old solar epoch rather complete models 1994-1997 that saw the impact of system objects made of primordial were made of the fluorescence of Comet Shoemaker-Levy 9 on ice and dust, generally in unstable the CN, CH, OH, and C2 Jupiter (1994), the apparition of orbits and intensively interacting radicals. The advent of high Comet Hyakutake that passed with the solar electromagnetic resolution spectroscopy in the late only 15 million km from the and corpuscular radiation. 1950's allowed the identification Earth (1996), as well as the Finally, the space missions to of many unknown lines, most of bright Comet Hale-Bopp that was P/Giacobini-Zinner in 1985 and which were due to C2 and NH2. discovered in 1995 and put on a especially to P/Halley in 1986 It is worth mentioning here that marvellous display when it passed provided the first in situ this effort has never been carried perihelion in early 1997. It observations of comets and through to completion and many includes some references to major dramatically widened our observed cometary spectral lines papers in this period (by author of scientific horizon, but also posed have still not been assigned an year of publication), but the many new questions which are emitter; the most likely are CO+, original version of this review in yet to be answered. CO2+ and C3 in the near-UV, C2 Astronomy & Astrophysics and NH2 in the optical and NH2 Reviews must be consulted for the 1952 - 1984: The modern era and H2O+ in the IR. full details about these. Following the break-throughs in 1950-51, the entire concept about The following Sections, divided comets had to be revised. This according to the main areas of process was a gradual one, as new investigative thrust during this observational facts were collected, period, illustrate how cometary and also because these research over the most recent observations were becoming decades has vindicated the ideas increasingly quantitative, put forward in 1950-51. allowing a progressively more detailed verification of the new Continued on page 4 ideas. Although number density estimates for cometary comae had Contents Hale-Bopp 1997 March 28 Robert Bullen been derived since the time of Comet Section contacts 2 Wurm's investigations in the Section news 2 Introduction The history of 1930's, the figures obtained were Tales from the Past 3 cometary astronomy is naturally rather uncertain and their Professional Tales 8 divided into five major periods, reliability was limited by the lack Comet History (cont) 4 the transitions being marked by of quantitative studies about the Review of observations 10 important new insights. Before excitation mechanisms of the Comet hunting notes 18 1600, comets were essentially light. Thus it is not too BAA COMET SECTION NEWSLETTER 2 THE COMET’S TALE The Delta Effect 18 Observations of 109P/ 20 BAA COMET SECTION NEWSLETTER 2000 April 3 Comet Section contacts Director: Jonathan Shanklin, 11 City Road, CAMBRIDGE. CB1 1DP, England. Phone: (+44) (0)1223 571250 (H) or (+44) (0)1223 221400 (W) Fax: (+44) (0)1223 362616 (W) E-Mail: [email protected] or [email protected] WWW page : http://www.ast.cam.ac.uk/~jds/ Assistant Director (Observations): Guy Hurst, 16 Westminster Close, Kempshott Rise, BASINGSTOKE, Hampshire. (and also Editor of RG22 4PP, England. The Astronomer magazine) Phone & Fax: (+44) (0)1256 471074 E-Mail: [email protected] or [email protected] CCD Advisor: Nick James, 11 Tavistock Road, CHELMSFORD, Essex. CM1 5JL, England. Phone: (+44) (0)1245 354366 E-mail: [email protected] or [email protected] Photographic Advisor: Michael Hendrie, Overbury, 33 Lexden Road, West Bergholt, COLCHESTER, Essex, CO6 3BX, England Phone: (+44) (0)1206 240021 Subscription to the Section newsletter costs £5 for two years, extended to three years for members who contribute to the work of the Section in any way. Renewals should be sent to the Director and cheques made payable to the BAA. Those due to renew should receive a reminder with this mailing. Section news from the Director Dear Section member, more before my departure for the data allows me to quickly enter Antarctic. The first of these was more recent observations. I write this introduction on my a faint non Kreutz group object, way home from Antarctica at the whilst the second was a I hope to have the Section guide end of March. My visit this year moderately bright Kretuz group on comet observing reprinted was a relatively short one, and my member. This discovery during the autumn. If anyone has work went very smoothly. With it prompted Michael Oates to have a suggestions for additions or other approaching autumn in go and he soon spotted one, improvements do let me know. Antarctica the nights became though it turned out to have The Tycho catalogue is the best darker and longer throughout my already been discovered. Nothing source of magnitude information stay. Although a generally cloudy daunted he has continued and this has recently been summer, we did have a few clear searching and has found several upgraded and now has fainter nights in which to experience the more, including a couple in stars than in the first edition. I grandeur of the southern skies. archived SOHO observations. On have added a section on reporting Surprisingly light pollution is a my return from Antarctica I found discoveries, as it is important to problem about the station, as another whilst in the process of follow the correct steps if you there are a number of badly compiling material for this issue think you have made one. I plan designed floodlights which create of The Comet's Tale. to drop the CCD and considerable glare. However once photographic reporting forms you are over a bluff overlooking Comet LINEAR 1999 S4 offers because no-one has ever used the station the skies are truly the hope of a naked eye comet them. dark, the milky way is bright over the summer. Do make every enough to cast shadows and on effort to observe it, but when you I would like to develop a standard most moonless nights the faint send the observations up please for submitting CCD images in glow of the diffuse aurora is try to submit them by email in order to make it easier to archive visible to the south. either the ICQ format to me or the images from many observers. Unfortunately there were no TA format to Guy. Try to get it The standard needs to allow for comets to observe, but I was able exactly right as we both have the name of the comet, the name to spend time on the voyage north more than enough to do without of the observer, the date and time typing in the some more archival having to edit observations. of the image, the telescope and observations from TA for 1980 to There is a template for both camera details, the scale of the 1989. This was over 2200 formats on the section web page, image and different image types observations, bringing the total so copy this if you are uncertain. (gif, jpeg etc). It is good practice number up to over 28,000. Don’t worry if you don’t have to include much of this email – paper copy is still information on the image, but if My success in discovering one acceptable, but send your this is not possible an auxiliary SOHO comet was followed by two observations to me as the program file may be needed. that I use to enter the archival BAA COMET SECTION NEWSLETTER 4 THE COMET’S TALE A possible suggestion would be to Panther, Jonathan Shanklin, (Spacewatch), 1999 E1 (Li), 1999 name image files as David Storey, David Strange, H1 (Lee), 1999 H3 (LINEAR), comet_yyyymmddl_obs.img and Cliff Turk and Alex Vincent auxiliary files as 1999 J2 (Skiff), 1999 J3 comet_yyyymmddl_obs.txt, where and also from: Jose Aguiar, (LINEAR), 1999 K8 (LINEAR), comet is the comet identifier, Alexandr Baransky, Nicolas 1999 L3 (LINEAR), 1999 N2 yyyymmdd is the date, l the image Biver, John Bortle, Jean-Gabriel (Lynn), 1999 S3 (LINEAR), 1999 number taken by the observer on Bosch, Reinder Bouma, Nicholas S4 (LINEAR), 1999 T2 that date, obs the first three letters Brown, Paul Camilleri, Jose (LINEAR), 1999 T3 (LINEAR), of the observers surname, and Carvajal, R Ferrando, Stephen img the image format.