ESO SL9 NEWS BULLETIN ===================== Issue : 2 Date : Monday, July 11, 1994, 12:00 UT (14:00 CEST; 08:00 Chilean time) Items : 2-A: Last night at La Silla 2-B: How far are the fragments from Jupiter ? 2-C: Better orbits available 2-D: Observations in South Africa 2-E: Telescopes at the ESO Headquarters 2-A. LAST NIGHT AT LA SILLA It is now mid-winter in the southern hemisphere. This is the most unstable weather period in the southern Atacama desert where the ESO La Silla observatory is located. Nevertheless, the chances of having clear weather during most of the critical SL9 days are reasonable good; according to statistics, well above 50 percent of the nights should be useable for the types of observations to be carried out during this event. Yesterday, July 10, there were thin cirrus clouds above the ESO observatory, but they disappeared towards the late afternoon, and the past night was entirely clear. However, the "seeing" (the image sharpness that deteriorates with increasing atmospheric turbulence) was again ranging from bad (1.2 arcsec) to very bad (1.8 arcsec), with only a few moments below 1 arcsec (mediocre). The wind was unstable and peaked at 10 m/s, but later dropped to only 1 m/s. There is still plenty of ice everywhere on the mountain after the last snowfall, in spite of above-zero temperatures. >From La Silla, ESO-astronomer Olivier Hainaut remarks: "There is a nice, very young moon at the begining of night and the Moon-Venus-Jupiter alignment with the zodiacal light is spectacular! You can really "sense" the Ecliptic, the main solar system plane." The CCD camera installed some days ago at the 60 cm Bochum Telescope was used tonight for the first time by Uri Carsenty and Stefano Mottola (DLR, Berlin, Germany) to image Jupiter. There were no particular technical problems to mount the special interferometric filters. In spite of the poor seeing conditions, the observers are quite enthusiastic about the very good and promising test images that were obtained this night through H-alpha and CH4 (methane) narrow band filters. Another 15 min exposure of SL9 was obtained for astrometric purposes at the NTT by Felix Mirabel, Pierre-Alain Duc and Sylvain Chaty (Service d'Astrophysique, Commissariat a l'Energie Atomique, Saclay, France); special care was taken to ensure that the first impacting nucleus (A) was also in the field. This image is quite deep and has been cleaned and flat-fielded, and the light contamination by Jupiter has been removed. It will be available from ESO later today (as ESO Press Photo SL9J/94-06). The comet train is getting longer and longer, and no longer fits into the wide 10 x 10 arcmin EMMI field of view. 2-B. HOW FAR ARE THE FRAGMENTS FROM JUPITER ? This is one of the most frequent questions asked by media and the public at this moment. Through the kind services of Brian Marsden (IAU Bureau for Astronomical Telegrams, Smithsonian Astrophysical Observatory, Cambridge, Mass., USA) we have asked Syuichi Nakano (Sumoto, Japan) to make such a computation. While Brian Marsden was the first to indicate the 1992 Jupiter approach by comet SL9 and also that this comet was actually in orbit about Jupiter, Syuichi Nakano was the first to home in on the 1992 date and to indicate that the 1994 Jupiter approach might be at least as close. The full table is available at the ESO WWW Portal; here are the data for those nuclei which will hit first. The distances are expressed in kilometres between the fragments and the centre of Jupiter and have been rounded to the nearest 1000 km: Date (UT) Nucleus A Nucleus B Nucleus C Nucleus D Nucleus E 1994 7 11.5 4,807,000 4,977,000 5,079,000 5,191,000 5,272,000 1994 7 12.0 4,504,000 4,680,000 4,785,000 4,901,000 4,984,000 1994 7 12.5 4,189,000 4,371,000 4,480,000 4,600,000 4,687,000 1994 7 13.0 3,860,000 4,051,000 4,164,000 4,289,000 4,379,000 1994 7 13.5 3,516,000 3,716,000 3,834,000 3,965,000 4,058,000 1994 7 14.0 3,153,000 3,364,000 3,489,000 3,626,000 3,724,000 1994 7 14.5 2,767,000 2,992,000 3,125,000 3,270,000 3,373,000 1994 7 15.0 2,350,000 2,594,000 2,736,000 2,891,000 3,001,000 1994 7 15.5 1,891,000 2,161,000 2,317,000 2,485,000 2,604,000 1994 7 16.0 1,366,000 1,678,000 1,854,000 2,041,000 2,171,000 1994 7 16.5 706,000 1,109,000 1,321,000 1,540,000 1,690,000 1994 7 17.0 309,000 643,000 937,000 1,125,000 1994 7 17.5 336,000 2-C. BETTER ORBITS AVAILABLE New orbits for the individual cometary fragments were computed yesterday by Don Yeomans and Paul Chodas (JPL/Caltech); they are based on the latest observations, of which many were obtained at ESO, up to and including July 10. They show that there are only minor changes to the impact timings published on July 5 (except for fragment V). The corresponding uncertainties will now clearly become much smaller. We hope to publish the new timings tomorrow. 2-D. OBSERVATIONS IN SOUTH AFRICA While setting up the link to the observers at the SAAO in Sutherland, South Africa, we have learned from the Director of that observatory, Bob Stobie, that observations are now planned at all four telescopes, as follows: 1.9m + IR photometer: times series photometry of one of Jupiter's moons searching for infrared flashes. (Dr. C. D. Laney, SAAO); 1.0m + CCD + coronagraph: images of comet fragments as they approach Jupiter, images of Jupiter after impact rotates into view, narrow band sodium filter to search for plumes from the impact. (Dr. M. Senay, Univ. of Hawaii); 0.75m + infrared camera: infrared imaging of Jupiter. (Dr Kaz Sekiguchi SAAO); and 0.5m + optical photometer: times series photometry of one of Jupiter's moons. (Dr P. Martinez, Univ of Cape Town). It is also planned to set up a media contact point at Sutherland. 2-E. TELESCOPES AT THE ESO HEADQUARTERS ESO is pleased to announce that arrangements have been made for observations of Jupiter, also from the ESO Headquarters in Garching, before and during the international Press Conference which takes place there on July 16, commencing at 20:00 CEST. The Bavarian company "Teleskoptechnik Halfmann" that builds advanced amateur telescopes will set up four telescopes outside the ESO building: One MT-86 - 0.86 metre Newton Mobile Telescope with 0.2 m refractor for visual observations; One MT-16 36 cm Newton Mobile Telescope with a TV-camera for video transmission to the auditorium where the Press Conference takes place; Two 15 cm Maksutov-Cassegrain telescopes for visual observations. Jupiter will not be very high in the sky, but in this way the media will be able to perform "observations" during the A-impact, just before 22:00 CEST. ---------- 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