------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 858 1994 July 17 17.55UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074 INTERNET: GMH at AST.STAR.RL.AC.UK or GMH at GXVG.AST.CAM.AC.UK ------------------------------------------------------------------- PERIODIC COMET SHOEMAKER-LEVY 9 (1993e)/COLLISION WITH JUPITER Mark Kidger, Teide Observatory reports: Detection with Spanish telescopes of the impact of Comet (1993e). At 20:18UT on 1994 July 16 a spot was detected on Jupiter in the position corresponding to the impact site of the first fragment of the comet (Nucleus A or 21). This observation was made by astronomers at the Instituto de Astrofisica de Canarias (IAC) with the 1.5m Carlos Sanchez, infrared telescope and with the 82cm IAC-80 Telescope, both in Teide Observatory (Tenerife); a near-simultaneous detection was made by IAC astronomers, collaborating with a French group from the Service d'Astrophysique (CEA) in the 2.56m Nordic Optical Telescope at El Roque de los Muchachos Observatory (La Palma). The detection was first made in the infrared and then, later, in the visible. According to the Central Bureau for Astronomical Telegrams of the IAU, this was the first report received of a detection of the impact from anywhere in the world. The spot was extraordinarily bright, slightly less than the satellite Io in the infrared and was between 20 and 30 thousand kilometres in length, rather larger than the Great Red Spot. The bright spot was very short lived: after 15 minutes, two of the three telescopes had virtually lost it from view. However, two hours later, a very faint cloud was still visible, a remnant of the explosion. This spot moved across the disk much more slowly than the visible cloud features, demonstrating that it is in the stratosphere of the planet, well above the visible clouds. Despite careful observation of Jupiter with optical telescopes (the 82cm IAC-80 Telescope and the 45cm Gregory Solar Tower: both in Teide Observatory, Tenerife) and telescopes in South Africa, the cloud was not seen clearly until some two and a half hours later. The observations appear to suggest that a bubble of hot gas formed above the impact site, but that the gas was not hot enough to emit significantly in the visible, emitting mainly in the infrared range. Shortly after appearing, the gas cooled and ceased emitting strongly in the infrared. The faint spot that has been seen since appears to be a cloud that has formed at very high altitude. the delay in the movement of the spot with respect to the Great Red Spot which was simultaneously visible in the disk indicates that the rotation of the upper atmosphere of Jupiter is very slow compared to the lower levels. Without doubt, the observations, which will now have to be analysed in great detail, are going to provide a lot of headaches for scientists who study them. The success of the observations and the possible detection in Japan of a radio event corresponding to the impact of a small fragment two days ago (this fragment would have been well outside the main body of the comet) suggests that, although the visible detection of the impacts will be very difficult, the infrared telescopes are going to view an ever more impressive spectacle, especially when the impacts of the largest fragments take place next Monday and Wednesday. Guy M Hurst --- 00017 --- Date: 18 Jul 1994 12:20:09-BST