Optical Observations of Comet 67P/Churyumov-Gerasimenko

Abstract

From optical longsplit spectra of comet 67P(Churyumov-Gerasimenko, obtained in February 1996, a CN production rate of (1.4 ± 0.4)· 10_25 l/sec was determined. From the continuum flux in the spectra the dust color and activity was determined. The dust color was neutral between 4070 Å and 4600 Å and the afrho parameter was (428 ± 60) cm. The production rate and Afrho value were similar to the values during the 1982 perihelion passage at similar heliocentric distances, indicating that the activity of comet 67P/Churyumov-Gerasimenko did not change significantly during recent orbital passages. The dust mass production rates were computed and a high mean dust to gas mass ratio of 4.8 was derived. R-filter images obtained in March 2003 were used to study the dust coma morphology. These images revealed the presence of two jet structures in the coma, not varying during our observation period. The orientation of the stationary structures could possibly be caused by one active area on the surface of the nucleus and an inclination of the projected rotation axis of approximately 40° with respect to the orbital plane.