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University of Arizona News Services

From: Lori Stiles, UA News Services, 520-621-1877,

Contact(s): Uwe Fink, 520-621-2736 or -2692
March 17, 1997

In the shadow of Hale-Bopp: tricky views of dimmer comets

While the world is enjoying the first Hale-Bopp Comet Show in 4,000 years, Uwe Fink and his graduate students have been taking scientists' best shot so far at getting spectra on two far dimmer, but also important comets.

Comet Wirtanen made no headlines last Friday, March 14, with its latest close swing by the sun, a distance of more than 159 million kilometers. Invisible to the naked eye or the amateur telescope, hundreds of thousands times dimmer than Hale-Bopp, Wirtanen is the target of the European Space Agency's Rosetta mission in 2011. Wirtanen makes a complete orbit around the sun once every 5.46 years.

Comet Wild 2 will make its closest swing by the sun at almost 224 million kilometers on Tuesday, May 6. Thousands of times dimmer than Hale-Bopp, Wild 2 is the target of a comet sample return mission, called Stardust, in January 2004. One goal of the mission is to capture and return to Earth with a thousand particles of Wild 2, a "fresh" comet filled with clues to early solar system formation. Wild 2 orbits the sun once every 6.17 years.

Fink, a professor at The University of Arizona Lunar and Planetary Laboratory, has just obtained some of the first spectra on Wild 2, according to a scientist with the NASA Jet Propulsion Lab, which manages the Stardust mission.

Fink and his graduate students, Michael Hicks and Ron Fervig, use a spectrometer especially designed by Fink at the UA's 61-inch telescope at Mount Bigelow in the Santa Catalina Mountains north of Tucson to measure the rate at which molecules of gas and dust blow out from the comets as they fly sunward. Government space agencies need to know how active these comets are to plan successful spacecraft flybys.

Not only are these kinds of observations difficult to make, Fink says, it takes months of intensive analysis to get good numbers on comet "production rates" of dust, water vapor, ammonia, and other gases. The trickiness of the observations is compounded by the fact that the astronomers have a brief window of opportunity for observing some of their targets. Wirtanen, for example, will be viewable with the 61-inch telescope only 40 minutes a night during Fink's next observing run, March 28 - April 1.

(EDITORS NOTE: Carloads of UA undergraduate students will join Fink, Hicks, Fervig and William Gundy, a recent UA graduate in planetary sciences, at the Mount Bigelow telescope March 30 and 31. The Hale-Bopp comet makes its closest swing by the sun, a distance of 137 million kilometers, on Monday night, March 31. With clear weather, there will be historic comet viewing both inside and outside the 61-inch Bigelow telescope dome.)

Last Updated: November 26, 2003
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