DPS 34th Meeting, October 2002
Session 7. Centaurs and Kuiper Belt Objects I
Oral, Chair(s): M.E. Brown and D.P. Cruikshank, Monday, October 7, 2002, 2:30-3:30 and 4:00-4:30pm, Ballroom

[Previous] | [Session 7] | [Next]

[7.01] Giant Kuiper Belt Object (20000) Varuna

D. Jewitt, S. Sheppard, H. Aussel (Institute for Astronomy)

Through a concerted observational campaign using optical and submillimeter telescopes on Mauna Kea, we have determined the size, albedo, color, rotation period, and sky-plane projected axis ratio of Kuiper Belt Object (20000) Varuna. We find a large (diameter = 900+/-140 km), elongated (axis ratio 1.5:1) and dark object (red albedo 0.07(+0.03/-0.02)) with a uniformly reddish surface (V-R = 0.64 +/-0.01) in a state of rapid rotation (period P = 6.3442+/-0.0002 hr).

The large size, short period and elongated shape suggest that Varuna is rotationally distorted. If so, the best fitting Jacobi ellipsoid equilibrium model yields a bulk density of only 1000 kg/m-3. Given that water and denser, refractory materials must be present in cosmic proportions, this low bulk density requires an internal void space (porosity) of 10% to 30%.

Varuna may be a rotationally distorted rubble pile, with a weak and porous internal constitution due to fracturing by ancient impacts. The high specific angular momentum implied by our observations and recent detections of several binary trans-Neptunian objects both point to an early, intense collisional epoch in which large trans-Neptunian objects were ~100 times more abundant than now. This epoch presumably coincided with the termination of the growth phase in the Kuiper Belt.

Work supported by the National Science Foundation.

Jewitt, D., Aussel, H., and Evans, A. (2001). Nature, 411, 446-447.

Jewitt, D. and Sheppard, S. (2002). Astronomical Journal, 123, 2110-2120.

If the author provided an email address or URL for general inquiries, it is as follows:

[Previous] | [Session 7] | [Next]

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