Infrared Observations Of Volatile Molecules In Comet Hale-Bopp |
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Authors: | Crovisier J |
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Institution: | (1) Observatoire de Paris-Meudon, F-92195 Meudon, France |
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Abstract: | Infrared observations of comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp) benefited from the high spectral resolution
and sensitivity of échelle spectrometers now equipping ground-based telescopes and from the availability of the Infrared Space
Observatory (ISO).
From the ground, several hydrocarbons were unambiguously detected for the first time: CH4, C2H2, C2H6. Water was observed through several of its hot vibrational bands, escaping telluric absorption. CO, HCN, NH3 and OCS were also observed, as well as several radicals. This permitted the evaluation of molecular production rates, of
rotational temperature, and — taking advantage of the 1-D imaging of long-slit spectroscopy — of the space distribution of
these species. With ISO, carbon dioxide was directly observed for the second time in a comet (after its detection from the
Vega probes in P/Halley). The spectrum of water was investigated in detail (several bands of vibration and far-infrared rotational
lines), permitting the evaluation of the rotational temperature of water, and of it spin temperature from the ortho-to-para
ratio. Water ice was identified in the grains of Hale-Bopp as far as 7 AU from the ground and possibly at 3 AU with ISO. The
composition of cometary volatiles appears to be strikingly similar to that of interstellar ices.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | C/1995 O1 Hale-Bopp comets ice infrared spectroscopy molecules |
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