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Abbreviated Journal Title

Astrophys. J. Lett.

Keywords

Comets: General; Minor Planets; Asteroids; Spectroscopic Survey; 2005 Ud; Asteroids; Surface; Family; Population; Phaethon; Nucleus; Object; Astronomy & Astrophysics

Abstract

We present the determination of the geometric R-band albedos of two main-belt comet (MBC) nuclei based on data from the Spitzer Space Telescope and a number of ground-based optical facilities. For 133P/Elst-Pizarro, we find an albedo of p(R) = 0.05 +/- 0.02 and an effective radius of r(e) = 1.9 +/- 0.3 km (estimated semiaxes of a similar to 2.3 km and b similar to 1.6 km). For 176P/LINEAR, we find an albedo of p(R) = 0.06 +/- 0.02 and an effective radius of r(e) = 2.0 +/- 0.2 km (estimated semiaxes of a similar to 2.6 km and b similar to 1.5 km). In terms of albedo, 133P and 176P are similar to each other and are typical of other Themis family asteroids, C-class asteroids, and other comet nuclei. We find no indication that 133P and 176P are compositionally unique among other dynamically similar (but inactive) members of the Themis family, in agreement with previous assertions that the two objects most likely formed in situ. We also note that low albedo (p(R) < 0.075) remains a consistent feature of all cometary (i.e., icy) bodies, whether they originate in the inner solar system (the MBCs) or in the outer solar system (all other comets).

Journal Title

Astrophysical Journal Letters

Volume

694

Issue/Number

2

Publication Date

1-1-2009

Document Type

Article

Language

English

First Page

L111

Last Page

L114

WOS Identifier

WOS:000264196600005

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