Optical observations of Comet 67P/Churyumov-Gerasimenko

Abstract

From longslit spectra obtained during the 1996 perihelion passage of Comet 67P/Churyumov-Gerasimenko, a CN production rate of (1.35 ± 0.35) × 1025 molecules s-1 was determined and an upper limit for the C3 production rate of 1 × 1025 molecules s -1 was derived. The dust color and dust activity were determined from the continuum light in the spectra. A neutral dust color was determined between 4070 Å and 4600 Å. The CN production rate and the Afρ parameter, determined to (428.2 ± 59.8) cm, were similar to the values of the 1982 perihelion passage, indicating that the comet's activity did not change significantly in recent orbital passages. A first crude estimate of the dust production rate indicates a high dust to gas mass ratio. R-filter images taken in March 2003 were used to study the dust coma morphology. Two jet structures were seen in the coma; these structures show no variations within the observing period from March 7 to May 30, 2003. The orientation of these stationary structures suggests an inclination of the rotation axis of the nucleus of approximately 40° with respect to the orbital plane.