DPS 34th Meeting, October 2002
Session 17. Centaurs and Kuiper Belt
Poster, Chair(s): , Tuesday, October 8, 2002, 3:30-6:00pm, Exhibit Hall

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[17.03] The size and albedo of KBO 2002 AW197

J. L. Margot, C. Trujillo, M. E. Brown (California Institute of Technology), F. Bertoldi (Max-Planck-Institut für Radioastronomie)

The discovery of the Kuiper belt object 2002 AW197 by Trujillo and Brown in January 2002 was announced in MPEC 2002-O30. We measured the diameter and albedo of this object by combining measurements of its reflected light and thermal emission. Photometric observations were performed at the Palomar 60-inch telescope and showed that the object has no detectable lightcurve (Trujillo and Brown, in prep.). Thermal emission observations at 1.2 mm wavelength were made using the Max-Planck Millimeter Bolometer (MAMBO) at the IRAM 30 m telescope on Pico Veleta (Spain). Pointing and ephemeris uncertainties were much less than the 10.6 arcsec beamwidth, and the weather conditions were good with zenith opacities less than ~0.2. Average sensitivity was 30 mJy s1/2, and the KBO was clearly detected with a statistical significance of ~4 sigmas.

Our estimate for the diameter of the KBO is 886+115-131 km, which makes it slightly smaller than the largest main-belt asteroid 1 Ceres (~950 km). The red geometric albedo is estimated to be 0.101+0.038-0.022, more than twice the 4% value traditionally assumed for KBOs. Kuiper belt objects may display a wide variety of albedos, as their surfaces likely endure a combination of processes including radiation mantling and impact resurfacing.

The values reported for 20000 Varuna are a diameter of 900+129-145 km and an albedo of 0.070+0.030-0.017 [1]. We note that both objects have relatively high inclinations (~ 20 degrees). Trujillo and Brown [2] reported a correlation between the inclination and color in the classical Kuiper belt, which possibly emphasizes the role of collisions in altering KBO surfaces.


[1] Jewitt, Aussel and Evans, Nature, 411, 2001. [2] Trujillo and Brown, ApJ Letters, 566, 2002.

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