The infrared spectrum of comet C/1995 O1 (Hale-Bopp) at 4.6 AU from the Sun.
Altieri, B.; Jorda, L.; Lamy, P. L.; Keller, H. U.; Lellouch, E.; Crovisier, J.; Bockelee-Morvan, D.; Leech, K.; Brooke, T. Y.; Hanner, M. S.
Abstract
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 2.5-12μm spectrum was recorded at low resolution. We present here the preliminary results of this observation. The 2.5-5μm spectrum shows emission in the CO_2_ ν_3_ band. The CO_2_ production rate is about 1.3x10^28^ s^-1^. The 6-12μm spectrum shows thermal emission at a colour temperature of 162K (6-8μm range) and a strong silicate band around 10μm, with a narrow feature at 11.2μm indicative of crystalline silicates.