Photometry and Imaging of Comet C/2004 Q2 (Machholz) at Lulin and La Silla

Kurzfassung

Aims.We have investigated the development of the dust and gas coma of the comet C/2004 Q2 (Machholz) from December 2004 to January 2005 using observations obtained at the Lulin Observatory, Taiwan and the European Southern Observatory at La Silla, Chile. Methods.We determined the dust-activity parameter Afp and the dust color and derived Haser production rates and scale lengths of C ₂ and NH₂. An image enhancement technique was applied to study the morphology of the gas and dust coma. Results.Two jets were observed in the coma distributions of C₂ and CN of comet Machholz that were not formed in the dust coma. The jets showed a spiral-like structure and pointed at different position angles at different observing times. The formation of these jets can be explained by the presence of two active surface regions on a rotating cometary nucleus.