The thermal emission of comet C/2013 A1 (Siding Spring) was observed on March 31, 2013, at a heliocentric distance of 6.48 au using the PACS photometer camera of the Herschel Space Observatory. The comet was clearly active, showing a coma that could be traced to a distance of ∼1000″, i.e. ∼50 000 km. Analysis of the radial intensity profiles of the coma provided a dust mass and dust production rate and the derived grain size distribution characteristics indicate an overabundance of large grains in the thermal emission. We estimate that activity started about 6 months before these observations at a heliocentric distance of ∼8 au.
- C/2013 A1 (Siding Spring) - Comets
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science