Thermal physics of asteroids. I. Effects of shape, heat conduction and beaming.
Abstract
With new technology and space observatories, IR-astronomy has the possibility to become a powerful tool for the investigation of the smaller bodies in the solar system. In order to respond to these expectations it is becoming very important to improve the theoretical understanding of the thermal physics of the asteroids. For example, the often used Standard Thermal Model (STM) is too crude for many applications. Therefore, a new thermal model for asteroids is described, which takes shape, pole orientation, heat conduction, and beaming into account. The model is applied to fictitious asteroids spanning a range of parameters, as well as to the arbitrarily chosen asteroid 43 Ariadne, in order to investigate general and practical aspects. This exercise demonstrates how heat conduction decreases the mean flux and amplitude of thermal light curves of asteroids. The heat conduction at the surface of a non-spherical asteroid induces imbalances between the absorbed and the emitted energy, which may have consequences for diameter determinations relying on equilibrium. The surface roughness - here described by spherical craters - causes the beaming of the thermal emission towards the Sun. The beaming also increases the amplitude of the thermal light curve, and is in itself enhanced for elongated asteroids. The otherwise time consuming heat diffusion problem is solved numerically once for a range of possible configurations, and the results are stored as Fourier series in interpolation tables. The computational speed has been one design criterion, since it is essential for the modeling of both individual asteroids and the thermophysical behaviour of asteroids in general.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1996
- Bibcode:
- 1996A&A...310.1011L
- Keywords:
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- ASTEROIDS;
- CONDUCTION;
- RADIATION MECHANISMS: THERMAL;
- INFRARED: SOLAR SYSTEM