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UA Observers of SL9 Impact


From Lori Stiles, News Services
University of Arizona
-- Sent July 17, 1994 10 a.m. MST


The Comet Impact Network Experiment (CINE) was in place at nine observatories around the globe to observe the effects of Comet Shoemaker-Levy 9 as the first fragment, A, flew into the planet yesterday. "Vitually all sites had problems of some sort in adapting their coronagraph/spectrographs to the various telescopes, but in all cases, help from the local collaborators and observatory support staff has been superb in overcoming the glitches," says CINE project leader Stephen M. Larson of the UA Lunar and Planetary Laboratory. "The next several days will be very busy for the CINE observers," he adds.

The CINE scientists are connected via the Internet and are forwarding news to NASA and the UA by email.

"In general, the weather has been better in the northern hemisphere sites and cloudy in the southern," Larson reports. The first impact was observable from Wise Observatory, Mitzpe Ramon, Israel, and reported yesterday by UA observer James V. Scotti. It also was observable in daylight from La Palma Observatory, says Larson, whose team is at the United Kingdom's 4.2-meter William Herschel telescope, but no flash reflection off Jupiter's moon, Europa, was seen in a preliminary look at the data.

"The La Palma effort was limited by the fact that twilight telescope time generously given by the scheduled observers was the first light through the instrument and adjustments had to be made in a hurry," Larson says. "As the impact site rotated into view, infrared detectors of other observers at several sites recorded the hot gases from the impact." Visible light images from another telescope at La Palma showed a ring expanding from the impact site, he adds.

UA astronomy professors Marcia J. Rieke and George M. Rieke are observing Comet SL9 with an infrared spectrometer and an infrared guide camera at the UA Steward Observatory's 90-inch telescope on Kitt Peak. Their primary science objective is to monitor any changes in the aurorae of Jupiter on comet impact. Their observing team includes Milagros Ruiz, Chad Engelbracht and telescope operator Patrick Frawley.

"By the time Jupiter had risen above the horizon in Arizona (on July 16), the impact (by fragment A) had already occurred," George Rieke reports. "We could see a bright spot in the infrared where the released energy had disturbed the atmosphere of the planet. We watched this spot move with Jupiter's rotation until it disappeared around the limb of the planet, some five hours after the impact. Observers in Hawaii later reported the reappearance of the disturbed area on the opposite limb of the planet about 11 hours after the impact. Our spectra showed the bright disturbance ot be material lifted so far above the atmosphere of Jupiter that it reflected sunlight without the strong absorptions by methane that usually dominate our view of the planet in the infrared.

"It seems likely that we are seeing clouds that condensed from material thrown out of the planet by the energy released by the impact. Further analysis of our data should let us determine what material these clouds consist of. We also observed the impact of the second (fragment B), and brighter, piece of the comet. It did not release enough energy to produce a signficant disturbance. It would appear that piece A was a massive chunk of comet that was not very reflective, while piece B was a highly reflective but not very massive piece. As a result, we do not know which of the following pieces will be massive enough to release a lot of energy and which will be so light they will essentially disappear without a trace; since the predictions were wrong for piece A, they are likely to be wrong again."

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