DPS 34th Meeting, October 2002
Session 9. Centaurs and Kuiper Belt Objects II
Oral, Chair(s): D. Jewitt and R. Millis, Monday, October 7, 2002, 4:30-6:00pm, Ballroom

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[9.05] Discovery of Trans-Neptunian Binaries with the Hubble Space Telescope

K. Noll, D. Stephens (STScI), W. Grundy, R. Millis, M. Buie, J. Spencer (Lowell), S. Tegler (NAU), W. Romanishin (U. OK), D. Cruikshank (NASA/Ames)

We have discovered binary companions to two trans-Neptunian objects (TNOs), 1997 CQ29 and 2000 CF105. The objects were observed as part of a photometric survey of TNO colors using the WFPC2 camera on Hubble (see Stephens et al. poster for details). Subsequent observations from HST and the ground have confirmed both detections.

Eight trans-Neptunian binaries (TNBs) are now known (including Pluto/Charon). The properties of known TNBs differ markedly from binaries in the main asteroid belt and near-Earth asteroid populations. The TNBs identified so far are more widely separated and more nearly equal in size, both qualities that enhance the probability of detection. In our survey, a reasonably uniform sample, we detected 3 binaries out of 76 observed objects, or a rate of 4±2% . Our sensitivity to companions was for a brightness difference of \Deltam <1 mag and separation a > 0.2 arcsec. Higher rates of detection by deeper surveys suggest that this value is a lower limit on the frequency of TNBs.

Photometry of individual components of the binaries was performed. Colors of the objects were found to be typical for TNOs. Followup observations suggest that both systems have relatively long orbital periods. In the case of 1997 CQ29 the existing data suggests a significantly eccentric orbit.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.