Rotation-stimulated structures in the CN and C sub( 3) comae of comet 103P/Hartley 2 close to the EPOXI encounter

In late 2010, a Jupiter family comet 103P/Hartley 2 was the subject of an intensive world-wide investigation. On UT October 20.7, the comet approached the Earth within only 0.12 AU, and on UT November 4.6 it was visited by the NASA EPOXI spacecraft. The authors joined this international effort and organized a ground-based observing campaign with three key goals to: 1. measure the parameters of the nucleus rotation in a time series of CN; 2. investigate the compositional structure of the coma by comparing the CN images with nightly snapshots of C sub( 3); and 3. investigate the photochemical relation of CN to HCN, using the HCN data collected nearly simultaneously with our images. The images were obtained through narrowband filters using the two-meter telescope of the Rozhen National Astronomical Observatory. They observe shells, arc-, jet- and spiral-like patterns that are very similar for the CN and C sub( 3) comae. The CN features expanded outwards with the sky-plane projected velocities of between 0.1 km s super( -1) to 0.3 km s super( -1).