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Astron. Astrophys. 343, L87-L90 (1999)

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Letter to the Editor

Infrared spectral observations of comet 103P/Hartley 2 by ISOPHOT *

L. Colangeli 1, E. Epifani 1,2, J.R. Brucato 1, E. Bussoletti 3, C. DeSanctis 4, M. Fulle 5, V. Mennella 1, E. Palomba 1,6, P. Palumbo 3 and A. Rotundi 3

1 Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Napoli, Italy
2 Dipartimento di Ingegneria Aerospaziale, Università degli Studi "Federico II", P.le Tecchio, I-80100 Napoli, Italy
3 Istituto Universitario Navale, via A. De Gasperi 5, I-80133 Napoli, Italy
4 IAS - CNR, Via del Fosso del Cavaliere, I-00133 Roma, Italy
5 Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
6 Observatoire de Haute Provence de CNRS, F-04870 Saint Michel l'Observatoire, France

Received 15 December 1998 / Accepted 14 February 1999


Spectral observations in the 2.5-12 µm range of comet 103P/Hartley 2 were performed on 1 Jan. 1998 by the ISOPHOT instrument, on board the Infrared Space Observatory. The obtained spectrum evidences intense bands at 2.66 and 4.26 µm, attributable to H2O and CO2, respectively. The derived molecular production rates are Q(H2O) = (3.1 [FORMULA] 0.2) [FORMULA] 1028 molec. s-1 and Q(CO2) = (2.5 [FORMULA] 0.3) [FORMULA] 1027 molec. s-1. This leads to a CO2/H2O abundance ratio of [FORMULA] 8%, showing that P/Hartley 2 is a relatively CO2 abundant comet, with respect to 1P/Halley and several other comets. A feature has been detected at 3.69 µm, whose attribution is rather puzzling. The long wavelength part of the spectrum is well fitted by a black-body profile at 285 K colour temperature. No significant silicate emission feature around 10 µm is observed, within observation errors.

Key words: comets: individual: 103P/Hartley 2 – infrared: solar system

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA.

Send offprint requests to: L. Colangeli

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999