ESO SL9 NEWS BULLETIN ===================== Issue : 1 Date : Sunday, July 10, 1994, 12:00 UT (14:00 CEST; 08:00 Chilean time) Items : 1-A: About this Bulletin 1-B: Last night's observations at La Silla 1-C: Impacts of the missing fragments ? 1-D: Dust particles hit Jupiter 1-E: Interest in this event 1-A. ABOUT THIS BULLETIN As announced in the ESO SL9 Brochure about the comet Shoemaker-Levy 9/Jupiter collision (published on July 6, 1994), from now on the ESO Information Service will on issue daily bulletins about the latest developments. The information is selected from various sources, including international computer newsboards accessible to the astronomers participating in the international collaboration set up in connection with this unique astronomical event. Special emphasis will be placed on the observations conducted at the ESO La Silla observatory in Chile and the results thereof. News items in this bulletin may be copied and published freely, provided ESO is mentioned as the source. Reference to individual items in future issues will be made by the number of issue and the capital letter, preceding the title: e.g., this is item 1-A. The persons responsible for this service are astronomers Richard Hook (ST-ECF, Garching), Olivier Hainaut (ESO, La Silla) and Richard West (ESO, Garching). 1-B. LAST NIGHT'S OBSERVATIONS AT LA SILLA The most recent image of the comet was obtained with the ESO 3.5-metre New Technology Telescope (NTT) by Mirabel and Duc, beginning on July 10, 02:31 UT. The exposure time was 15 min through a red filter at the ESO Multi-Mode Instrument (EMMI). It shows the sunlight reflected from the dust clouds surrounding comet fragments B - Q. This image is now being evaluated by astronomers at the ESO Headquarters in Garching. A quick look this morning does not indicate any obvious changes of the individual nuclei, except that fragment G is now clearly double; this splitting was first found at the end of June. The comet is thus on steady course for the fatal encounter. The first impact (of fragment A) is predicted to happen on July 16, 1994, at 19:54 UT (21:54 CEST; 15:54 Chilean time). The B-fragment which will be well observable from La Silla will hit seven hours later, on July 17, at 02:49 UT. At that time Jupiter will be about 40 degrees above the horizon at that site. Observations are becoming increasingly difficult as the comet is coming closer to Jupiter. The distance in the sky between the planet and the first fragment to collide with Jupiter is now only approx. 22 arcminutes. The actual distance in space is about 5 million kilometres. The comet observations are now strongly influenced by Jupiter's strong light and it is now getting rather difficult to obtain images of the fainter nuclei. Uri Carsenty and his co-observers have arrived at La Silla and will begin their observations with the 60-cm Bochum telescope this evening. This Programme is described in the ESO SL9 Brochure (# 8 on page 46). 1-C. IMPACTS OF THE MISSING FRAGMENTS ? Paul Chodas and Don Yeomans (JPL/Caltech) have provided new calculations for the impacts of the "missing" fragments, which disappeared from view earlier this year. Although they have probably disintegrated further, it is quite possible that some sizeable fragments may still be present whose impacts could possibly be observed. They find the following impact timings: Fragment Impact time (UT) Last seen J July 19, 02:40 December 1993 M July 20, 05:45 July 1993 P1 July 20, 16:30 March 1994 The estimated uncertainties are such that there is a 95 percent chance that the impacts take place within +- 2 hours of the indicated times. The J-impact takes place when Jupiter is situated well above the horizon of La Silla and may therefore be observable from there. 1-D. DUST PARTICLES HIT JUPITER NOW Zdenek Sekanina, Paul Chodas and Don Yeomans (JPL/Caltech) have called attention to the fact that, according to their models, cometary particles (dust) from comet Shoemaker-Levy 9 should now begin to interact with Jupiter. Some of the outermost dust particles in the impressive dust fan, first seen on the now famous March 30, 1993, image by Jim Scotti have already swung past the planet, but others are just now entering the magnetosphere and may cause disturbances in the radio emission from Jupiter. This emission is being actively monitored by large radio telescopes on the ground (South Africa, Australia, India, Ukraine, and other countries) as well as by the Ulysses and Voyager 2 spacecraft. 1-E. INTEREST IN THIS EVENT Everybody knows that there is a strong public interst in this event. But how do you measure this in numbers ? One possibility is provided by the statistics of remote computer access to the comet SL9 information area of the ESO WWW Portal. During the past 9 1/2 days, from the beginning of the month of July until this moment, there have been exactly 360 logins from different countries. This may be compared to 221 logins for the weather map of Europe. So it looks as if the comet is easily beating the weather ! ---------- This daily news bulletin is prepared for the media by the ESO Information Service on the occasion of the July 1994 collision between comet Shoemaker-Levy 9 and Jupiter. It is available in computer readable form over the ESO WWW Portal (URL: http://http.hq.eso.org/eso-homepage.html) and by fax to the media (on request only). News items contained therein may be copied and published freely, provided ESO is mentioned as the source. ESO Information Service European Southern Observatory Karl-Schwarzschild-Strasse 2 D-85748 Garching bei Muenchen Germany Tel.: +49-89-32006276 Fax.: +49-89-3202362