Transition Comets -- UV Search for OH Emissions in Asteroids

Hubble search for transition comets (Transition Comets—UV Search for OH Emissions in Asteroids) was a study involving amateur astronomers and the use of the Hubble Space Telescope. This was one of only six studies involving amateur astronomers that was approved by NASA.

In the beginning years of the Hubble Space Telescope (HST) project, NASA and Congress were interested in finding ways for amateur astronomers to participate in HST research. The director of the Space Telescope Science Institute (STScI), Riccardo Giacconi, decided to allocate some of his "Director's Discretionary" time to amateur observing programs. In December 1985, the leaders of seven national amateur astronomy organizations met at STScI in Baltimore to discuss the participation of amateur astronomers in the HST project.

The team used the Hubble Space Telescope to perform a spectroscopic search for OH emission from five asteroids. OH emission would indicate that the asteroids were once comets. 944 Hidalgo and 2201 Oljato move in elliptical, comet-like orbits. 182 Elsa, 224 Oceana, and 899 Jokaste are main-belt asteroids. The last three have been observed with coma (Kresak, 1977). Concurrently with the spectroscopic study, ground-based visual observations were carried out by 80 amateur astronomers in 22 countries.

Scientists suspect that some asteroids were once comets. A comet loses part of its mass with each passage around the Sun. It would appear that some would eventually use all of their volatiles, or perhaps cover these under a blanket of dust after repeated passages around the Sun. Such an object might then have an asteroid appearance.

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