238P/Read (P/2005 U1) is a main-belt comet discovered on 24 October 2005 by astronomer Michael T. Read using the Spacewatch 36-inch telescope on Kitt Peak National Observatory. It has an orbit within the asteroid belt and has displayed the coma of a traditional comet. It fits the definition of an Encke-type comet with (TJupiter > 3; a < aJupiter).
Orbit 238P/Read orbits the Sun on an elliptical orbit at an average distance of 3.17 astronomical units (AU). It is located in the outer main asteroid belt, taking 5.63 years to complete an orbit. With a moderate orbital eccentricity of 0.25, its distance from the Sun ranges from 2.37 AU at perihelion to 3.96 AU at aphelion. It has a low inclination of 1.3° with respect to the ecliptic plane. It has a chaotic orbit, with a low Lyapunov time of less than 100,000 years.
238P's orbital elements place it within a dynamical association of dark asteroids known as the Gorchakov family. The Gorchakov family (whose namesake and largest member is 5014 Gorchakov) is a relatively young asteroid family, and its proximity to several mean-motion resonances with Jupiter makes many of its members' orbits highly chaotic.
Description
238P was the second main-belt comet to be discovered. When it was discovered on 2005 October 24, it showed vigorous cometary activity until 2005 December 27. Outgassing likely began at least 2 months before discovery. The activity of is much stronger than 133P/Elst-Pizarro and 176P/LINEAR. This may indicate that the impact assumed to have triggered 's activity occurred very recently.
Observations of when it was inactive in 2007 suggests that it has a small nucleus only about 0.6 km in diameter.
It came to perihelion on 2011 March 10, 2016 October 22. and 2022 June 5. It will next come to perihelion on 2028 January 24.
was the target of a mission proposal in NASA's Discovery Program in the 2010s called Proteus, however it was not selected for further development. Discovery program's founding mission was to an asteroid, but it went to a Near-Earth asteroid. A mission to a main-belt asteroid was proposed in the 1990s (also see Deep Impact (spacecraft)).
The comet was observed by James Webb Space Telescope during the 2022 perihelion and it was found spectrographicaly that its coma was composed by water vapor, due to water sublimation, and lacked significant coma.
See also List of missions to comets
References
External links
238P/Read at the Minor Planet Center's Database 238P/Read at Seiichi Yoshida's website Main-Belt Comet 238P/Read Revisited (arXiv:1106.0045 : 31 May 2011)