240P/NEAT is a Jupiter-family comet with an orbital period of 7.61 years. It was discovered by Near Earth Asteroid Tracking (NEAT) on 7 December 2002.
The comet came opposition on 22 November 2025, and came to perihelion on 19 December 2025 when it was around magnitude 12-13.
Observational history The comet at discovery had an apparent magnitude of 18.4, and further observations revealed it had a coma about 8 arcseconds across and a tail 14 arcseconds long. The comet was spotted in prediscovery images dating from 5 October and 6 December by LONEOS and from 5 November by NEAT. Based on these observations it was recognised it is a periodic comet with an orbital period of 8.1 years. The comet was recovered independently by H. Taylor, H. Sato, Leonid Elenin, and T. Yusa on 9, 10, 11, and 11 August 2010 respectively, at an estimated magnitude of around 17. It received its official numerical designation (240P) alongside six other comets on August 2010.
The comet had a close approach to Jupiter on 10 July 2007 at a distance of which reduced the orbital period to 7.6 years and the perihelion distance from 2.5 to 2.1 AU. The comet experienced three events of significant brightening which last for three to six months during its next two perihelia, on March-April 2011, July-August 2017, and on November-December 2018. The events more likely are the result of the warming of previously insulated material due to the reduction of the perihelion distance. The new activity takes place in one or two locations of the nucleus.
240P-B
On 3 October 2025 fragment 240P-B was imaged by Kitt Peak and reported by V. Carvajal. 240P-B also came to perihelion on 19 December 2025, about 51 minutes after the main body and about farther from the Sun.
+2025 perihelion passage Fragment Perihelion time Perihelion distance240P-A 2025-Dec-19 22:52 240P-B 2025-Dec-19 23:43
The separation (∼108 m) and the rate of change of the separation (∼1 m s−1) of 240P-A from 240P-B point to splitting of the precursor nucleus at least three years before the present observations. The radius of 240P-B is uncertain, with a best estimate ∼300 m and an absolute lower limit 50 m. The mass loss of 240P-B peaked at ∼35 kg s−1 around perihelion, and the total ejected mass was . The likely cause of the splitting is rotational instability triggered by outgassing torques. Both 240P-A and 240P-B are liable to further breakup and destruction by rotational instability on timescales that are shorter than the timescale due to sublimation mass loss.
Notes
References
External links
at the Minor Planet Center database 240P/NEAT at the Comet OBServations Database 240P/NEAT at Gideon van Buitenen's website Fragment 240P-B as seen on 2 October 2025