162P/Siding Spring

162P/Siding Spring is a Jupiter-family comet with an orbital period of 5.3 years. It was discovered in images obtained on 10 October 2004 as part of the Siding Spring Survey.

Observational history

The comet was discovered during the Siding Spring Survey as an asteroidal object shining with an apparent magnitude of 14.1 but a tail extending for about 4 arcminutes was observed on 12 November 2004, indicating that it is a comet. The tail grew longer the next days, reaching a length of over 10 arcminutes on 15 November. Two days later the tail was fainter, and barely visible within one arcminute from the nucleus. On 21 October 2031, the comet will approach Earth at a distance of.

Physical characteristics

The comet was observed by NASA Infrared Telescope Facility in 2004, finding that the nucleus has an effective radius of km, which corresponds to a visual albedo of, and a reflectance spectrum typical of a D-type asteroid. Further observations by the Spitzer Space Telescope indicate an effective radius of 7.03 ± 0.48 km. This is one of the largest nuclei of Jupiter family comets with known radius. More detailed observations indicate that the nucleus has axis ratios a/b = 1.56 and b/c = 2.33, and could possibly have two lobes. The sidereal period of the comet is hours.