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J.A. Stansberry, D.P. Cruikshank (NASA Ames), W.G. Grundy (Lowell Observatory), J.L. Margot (Cornell), J.P. Emery (SETI Inst.), Y.R. Fernandez (U. Hawaii), G.H. Rieke (U. Arizona)
Our Spitzer detections of the thermal emission from a sample of Kuiper Belt objects (KBOs) and Centaurs at wavelengths of 24 and 70 \mum, combined with visible magnitudes, allow us to measure their visible albedos and the diameters. One KBO (47171, 1999 TC36) is a binary with a known orbital period and mass (Margot et al., this meeting). Combined with our diameter determination, their mass further allows a density determination for that object. Our initial results for a sub-sample of our targets are given in the table below (see also Cruikshank et al. AJ 624, 2005 re. 2002 AW197; and Stansberry et al. ApJS 154, 2004 re. 29P/Schwassmann-Wachmann 1). There is a remarkable diversity in albedo, and some indication that KBOs may generally have higher albedos than Centaur objects. We will discuss uncertainties and present refined values for these physical parameters, and place our results in the context of the visible colors and orbits of the targets.
Object
| Diam. (km)
| pv (%)
| Density (g/cc)
|
|
(15875) 1996 TP66
| 300--400
| 2--4
| |
|
(47171) 1999 TC36
| 325--425
| 11--19
| 0.55--0.8
|
|
(29981) 1999 TD10
| 75--105
| 5--10
| |
|
(55565) 2002 AW197
| 650--750
| 14--20
| |
|
(28978) Ixion
| 400--550
| 25--50
| |
|
(38628) Huya
| 430--530
| 9--13
| |
|
(20000) Varuna
| 450--750
| 12--30
| |
|
(60558) 2000 EC98
| 55--85
| 8--17
| |
|
(54598) 2000 QC243
| 150--200
| 4--7
| |
|
(42355) 2002 CR46
| 140--170
| 8--12
| |
|
(8405) Asbolus
| 70--85
| 8--11
| |
|
(10199) Chariklo
| 200--250
| 8--12
| |
|
(52872) Okyrhoe
| 40--50
| 2.5--3.5
| |
|
(32532) Thereus
| 75--85
| 8.5--11
|
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.