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C. A. Trujillo (Gemini Observatory), M. E. Brown (Caltech), D. L. Rabinowitz (Yale), T. R. Geballe (Gemini Observatory)
The two intrinsically brightest minor planets (i.e. highest absolute magnitude) were discovered less than a year ago in an ongoing outer solar system survey at Caltech. We present near infrared K band spectra of these bodies taken with the Gemini North 8-meter Telescope. Although both bodies have large absolute magnitudes, they are quite faint and difficult to study in the near infrared due to their extreme distance. The minor planet 2003 VB12 is the most distant known object bound to the sun by a factor of 1.6 and it has the brightest absolute magnitude as of this writing, August 2004. Using a Hapke grain model under a wide variety of grain diameter and albedo assumptions, we place upper limits on the surface area of water ice and methane ice that could be on 2003 VB12. We can rule out a Pluto-like (methane dominated) or Charon-like (water dominated) surface for 2003 VB12, despite likely similarity to Charon in diameter.
The minor planet 2004 DW is a Plutino and has the second brightest absolute magnitude of any currently known minor planet. The K band spectrum of 2004 DW shows pronounced water ice absorption. Best-fit models for the water ice under a variety of assumed albedos show that the surface fraction of water ice on 2004 DW is about 80% of the assumed K-band albedo. This amount of water ice on 2004 DW is smaller than that found on Charon and closer to amounts found on the surface of Triton. Our models also indicate that the albedo of 2004 DW must be less than 70% based on the water ice absorption observed, suggesting a body that is greater than 600 km diameter and likely visible in the thermal using existing technology.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.