Radioactive heating and layered structure of cometary nuclei |
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| Authors: | S Yabushita K Wada |
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| Institution: | (1) Department of Applied Mathematics and Physics and Department of Nuclear Engineering, Kyoto University, Kyoto, Japan |
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| Abstract: | Following the work of Whipple and Stefanik, radioactive heating by uranium, thorium and pottasium of a cometary nucleus is discussed. The assumed composition is that of interstellar medium. If thermal diffusivity is 10–4 cm2s–1, the central temperature of a nucleus with radius 10 km can be above 50 K, while if the thermal diffusivity is 5 × 10–3, the central temperature can be only 25 K or so. Volatile gases such as N2 and CO will flow toward the outer part of the nucleus and are lost in their first several approaches to the sun. This mechanism appears capable of explaining the depletion of N2 and CO relative to the interstellar abundance. It is argued that unfamiliar activity of comet Bowell could be explained by sublimation mainly of N2 and CO. |
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