Issue |
A&A
Volume 413, Number 3, January III 2004
|
|
---|---|---|
Page(s) | 1163 - 1175 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20031564 | |
Published online | 07 January 2004 |
Properties of the nuclei of Centaurs Chiron and Chariklo
Laboratoire d'Astronomie Spatiale, BP 8, 13376 Marseille Cedex 12, France
Corresponding author: O. Groussin, olivier.groussin@oamp.fr
Received:
12
February
2003
Accepted:
30
September
2003
We analyze visible, infrared, radio and spectroscopic
observations of 2060 Chiron in a synthetic way to determine the
physical properties of its nucleus. From visible observations
performed from 1969 to 2001, we determine an absolute V magnitude
for the nucleus of with an amplitude of
,
implying a nearly spherical nucleus with a ratio of semi-axes
. Infrared observations at 25, 60, 100 and 160 μm (i.e., covering the broad maximum of the spectral energy
distribution) obtained with the Infrared Space Observatory Photometer
(ISOPHOT) in June 1996 when Chiron was near its perihelion are
analyzed with a thermal model which considers an intimate mixture of
water ice and refractory materials and includes heat conduction into
the interior of the nucleus. We find a very low thermal inertia of
J K-1 m-2 s-1/2 and a radius of
km. Combining the visible and infrared observations, we
derive a geometric albedo of
. We find that the observed
spectra of Chiron can be fitted by a mixture of water ice (~30%) and refractory (∼70%) grains, and that this surface model
has a geometric albedo consistent with the above value. We also
analyze the visible, infrared and radio observations of Chariklo (1997
CU26) and derive a radius of
km, a geometric albedo of
and a thermal inertia of 0
J K-1 m-2 s-1/2. A mixture of water ice (
20%)
and refractory (
80%) grains is compatible with the
near-infrared spectrum and the above albedo.
Key words: minor planets, asteroids
© ESO, 2004
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