210P/Christensen
210P/Christensen is a Jupiter family comet with an orbital period of 5.7 years. It was discovered by Eric J. Christensen on 26 May 2003 in images taken by the Catalina Sky Survey and recovered in images obtained by STEREO, the first time a single-apparition comet was recovered by a spacecraft.
Observational history
Eric J. Christensen discovered the comet on 26 May 2003 in images taken with the 0.7-m Schmidt telescope of the Catalina Sky Survey. The comet had an estimated magnitude of 14.6 and a coma with an estimated diameter between 10 and 35 arcseconds and a faint tail. Further observations revealed the comet had a short orbital period.In mid December 2008, Australian comet-hunter Alan Watson spotted in the STEREO/SECCHI Heliospheric Imager HI-1B data a cometary object. Veteran German comet hunter Rainer Kracht recorded a few positions of the comet in the data and produced a set of very approximate orbital elements for it. Maik Meyer noticed the similarity of these orbital elements to those of P/2003 K2 and the link was confirmed by Brian G. Marsden. This was the first recovery of a single-apparition comet by a spacecraft. The comet was observed from the ground on 14 December 2008, located low and in bright twilight, and on 31 December 2008 it had an estimated magnitude of 10.5.
During the 2025 apparition, the comet passed from Earth on 8 November 2025 but was only 20 degrees from the Sun. It came to perihelion on 22 November 2025. It was visible in SWAN in November 2025 around magnitude 11. On 26 November it was visible low in the morning twilight, with a faint tail about a quarter of a degree long and an estimated magnitude of 9.5.
The comet has been locked in a 2:1 orbital resonance with Jupiter for the last 10,000 years and could be of asteroidal origin. Its nucleus is estimated to be about in diameter. It makes close approaches to Venus and on 17 September 1929 passed from Venus.