Astronomy and Astrophysics Letters dedicated to ISO

The infrared spectrum of comet C/1995 O1 (Hale-Bopp) at 4.6 AU from the Sun

J. Crovisier - T.Y. Brooke - M.S. Hanner - H.U. Keller - P.L. Lamy - B. Altieri - D. Bockelée-Morvan - L. Jorda - K. Leech - E. Lellouch


Comet C/1995 O1 (Hale-Bopp) was observed on 27 April 1996 with the ISOPHOT instrument of ISO when it was at 4.6~AU from the Sun. The 2.5-12 micron spectrum was recorded at low resolution. We present here the preliminary results of this observation. The 2.5-5 micron spectrum shows emission in the CO2 v3 band. The CO2 production rate is about 1.3 x 1028 s-1. The 6-12 micron spectrum shows thermal emission at a colour temperature of 162 K (6-8 micron range) and a strong silicate band around 10 microns, with a narrow feature at 11.2 microns indicative of crystalline silicates.

comets: general - comet: individual: C/1995 O1 (Hale-Bopp) - infrared: solar system

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