Thermal Emission From The Dust Coma Of Comet Hale-Bopp And The Composition Of The Silicate Grains |
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Authors: | Hanner M S Gehrz R D Harker D E Hayward T L Lynch D K Mason C C Russell R W Williams D M Wooden D H Woodward C E |
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Institution: | (1) MS 183-501 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA;(2) Astronomy Department, University of Minnesota, Minneapolis, MN 55455, USA;(3) Wyoming Infrared Observatory, Physics and Astronomy Department, University of Wyoming, Laramie, WY, 82071;(4) Astronomy Department, Cornell University, Ithaca, NY 14853, USA;(5) Aerospace Corporation, M2-266, P.O. Box 92957, Los Angeles, CA 90009-2957, USA;(6) MS 245-6 NASA Ames Research Center, Moffett Field, CA 94035-1000, USA |
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Abstract: | The dust coma of comet Hale-Bopp was observed in the thermal infrared over a wide range in solar heating (R = 4.9–0.9 AU)
and over the full wavelength range from 3 μm to 160 μm. Unusual early activity produced an extensive coma containing small
warm refractory grains; already at 4.9 AU, the 10 μm silicate emission feature was strong and the color temperature was 30%
above the equilibrium blackbody temperature. Near perihelion the high color temperature, strong silicate feature, and high
albedo indicated a smaller mean grain size than in other comets. The 8–13 μm spectra revealed a silicate emission feature
similar in shape to that seen in P/Halley and several new and long period comets. Detailed spectral structure in the feature
was consistent over time and with different instruments; the main peaks occur at 9.3, 10.0 and 11.2 μm. These peaks can be
identified with olivine and pyroxene minerals, linking the comet dust to the anhydrous chondritic aggregate interplanetary
dust particles. Spectra at 16–40 μm taken with the ISO SWS displayed pronounced emission peaks due to Mg-rich crystalline
olivine, consistent with the 11.2 μm peak.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Comet Hale-Bopp infrared dust silicates |
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