2060 Chiron is a ringed small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs—bodies orbiting between the asteroid belt and the Kuiper belt. Chiron is named after the centaur Chiron in Greek mythology.
In planetary astronomy, a centaur is a small Solar System body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets. Centaurs generally have unstable orbits because of this; almost all their orbits have dynamic lifetimes of only a few million years, but there is one known centaur, 514107 Kaʻepaokaʻawela, which may be in a stable orbit. Centaurs typically exhibit the characteristics of both asteroids and comets. They are named after the mythological centaurs that were a mixture of horse and human. Observational bias toward large objects makes determination of the total centaur population difficult. Estimates for the number of centaurs in the Solar System more than 1 km in diameter range from as low as 44,000 to more than 10,000,000.
4015 Wilson–Harrington is an active asteroid known both as comet 107P/Wilson–Harrington and as asteroid 4015 Wilson–Harrington. It passed 0.4 AU (60 million km) from Earth on 20 July 2022 and then passed perihelion on 24 August 2022. It seldom gets brighter than apparent magnitude 16. It will return to perihelion on 25 November 2026.
Comet Elst–Pizarro is a body that displays characteristics of both asteroids and comets, and is the prototype of active asteroids. Its orbit keeps it within the asteroid belt, yet it displayed a dust tail like a comet while near perihelion in 1996, 2001, and 2007.
8405 Asbolus is a centaur orbiting in the outer Solar System between the orbits of Jupiter and Neptune. It was discovered on 5 April 1995, by James Scotti and Robert Jedicke of Spacewatch (credited) at Kitt Peak Observatory in Arizona, United States. It is named after Asbolus, a centaur in Greek mythology and measures approximately 80 kilometers in diameter.
3200 Phaethon, provisionally designated 1983 TB, is an active Apollo asteroid with an orbit that brings it closer to the Sun than any other named asteroid. For this reason, it was named after the Greek Hero, Phaëthon, son of the sun god Helios. It is 5.8 km (3.6 mi) in diameter and is the parent body of the Geminids meteor shower of mid-December. With an observation arc of 35+ years, it has a very well determined orbit. The 2017 Earth approach distance of about 10 million km was known with an accuracy of ±700 m.
Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss, but their orbits remain within Jupiter's orbit. These bodies were originally designated main-belt comets (MBCs) in 2006 by astronomers David Jewitt and Henry Hsieh, but this name implies they are necessarily icy in composition like a comet and that they only exist within the main-belt, whereas the growing population of active asteroids shows that this is not always the case.
60558 Echeclus is a centaur, approximately 60 kilometers (37 miles) in diameter , located in the outer Solar System. It was discovered by Spacewatch in 2000 and initially classified as a minor planet with provisional designation 2000 EC98 (also written 2000 EC98). Research in 2001 by Rousselot and Petit at the Besançon observatory in France indicated that it was not a comet, but in December 2005 a cometary coma was detected. In early 2006 the Committee on Small Bodies Nomenclature (CSBN) gave it the cometary designation 174P/Echeclus. It last came to perihelion in April 2015, and was expected to reach about apparent magnitude 16.7 near opposition in September 2015.
7604 Kridsadaporn, provisional designation 1995 QY2, is an unusual, carbonaceous asteroid and Mars-crosser on a highly eccentric orbit from the outer regions of the asteroid belt, approximately 12 kilometers (7.5 miles) in diameter. It was discovered on 31 August 1995, by Australian astronomer Robert McNaught at Siding Spring Observatory near Coonabarabran, Australia. Due to its particular orbit, the C-type asteroid belongs to MPC's list of "other" unusual objects, and has been classified as an "asteroid in cometary orbit", or ACO. The asteroid was named in memory of Thai astronomer Kridsadaporn Ritsmitchai.
354P/LINEAR, provisionally designated P/2010 A2 (LINEAR), is a small main-belt asteroid that was impacted by another asteroid sometime before 2010. It was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) at Socorro, New Mexico on 6 January 2010. The asteroid possesses a dusty, X-shaped, comet-like debris trail that has remained nearly a decade since impact. This was the first time a small-body collision had been observed; since then, minor planet 596 Scheila has also been seen to undergo a collision, in late 2010. The tail is created by millimeter-sized particles being pushed back by solar radiation pressure.
238P/Read 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.
(612093) 1999 LE31, prov. designation: 1999 LE31, is a centaur and damocloid on a retrograde and eccentric orbit from the outer region of the Solar System. It was first observed on 12 June 1999, by astronomers with the LINEAR program at the Lincoln Lab's ETS near Socorro, New Mexico, in the United States. The unusual object measures approximately 17 kilometers (11 miles) in diameter.
Comets have been observed for over 2,000 years. During that time, several different systems have been used to assign names to each comet, and as a result many comets have more than one name.
(300163) 2006 VW139 (provisional designation 2006 VW139, periodic comet designation 288P/2006 VW139) is a binary active asteroid and main-belt comet from the outer regions of the asteroid belt. The object was discovered by Spacewatch in 2006. Its binary nature was confirmed by the Hubble Space Telescope in September 2016. Both primary and its minor-planet moon are similar in mass and size, making it a true binary system. The components are estimated to measure 1.8 kilometers in diameter, orbiting each other at a wide separation of 104 kilometers every 135 days.
324P/La Sagra is an active asteroid with an orbital period of 5.44 years. It has been found to be active in more than one perihelia, indicating that the source of activity is sublimation.
(457175) 2008 GO98 (provisional designation 2008 GO98) with cometary number 362P, is a Jupiter family comet in a quasi-Hilda orbit within the outermost regions of the asteroid belt. It was discovered on 8 April 2008, by astronomers of the Spacewatch program at Kitt Peak National Observatory near Tucson, Arizona, in the United States. This presumably carbonaceous body has a diameter of approximately 15 kilometers (9 miles) and rotation period of 10.7 hours.
P/2019 LD2 (ATLAS) is a Jupiter-family comet discovered by the Asteroid Terrestrial-impact Last Alert System on 10 June 2019. It was initially reported as the first known Jupiter trojan asteroid to display cometary activity, but its classification as a Jupiter trojan was retracted after closer examination and a longer observation arc revealed its orbit to be unstable like a typical Jupiter family comet and implied that its position near the trojans is temporary.
(248370) 2005 QN173 is a main belt asteroid that undergoes recurrent comet-like activity near perihelion, and is now designated comet 433P/(248370) 2005 QN173. This object was discovered on August 29, 2005 by the Near-Earth Asteroid Tracking program at Palomar Observatory. It orbits in the outer main asteroid belt with an orbital period of 5.36 years, a semi-major axis of 3.06 AU, and an orbital eccentricity of 0.225, bringing it as close as 2.37 AU to the Sun at perihelion. The orbital plane is inclined at an angle of 0.068° to the ecliptic.
P/2013 R3 (Catalina–PanSTARRS) was an active main-belt asteroid that disintegrated from 2013 to 2014 due to the centrifugal breakup of its rapidly-rotating nucleus. It was discovered by astronomers of the Catalina and Pan-STARRS sky surveys on 15 September 2013. The disintegration of this asteroid ejected numerous fragments and dusty debris into space, which temporarily gave it a diffuse, comet-like appearance with a dust tail blown back by solar radiation pressure. Observations by ground-based telescopes in October 2013 revealed that P/2013 R3 had broken up into four major components, with later Hubble Space Telescope observations showing that these components have further broken up into at least thirteen smaller fragments ranging 100–400 meters (330–1,310 ft) in diameter. P/2013 R3 was never seen again after February 2014.
483P/PanSTARRS is a pair of active main-belt asteroids that split apart from each other in early 2010. The brightest and largest component of the pair, P/2016 J1-A, was discovered first by the Pan-STARRS 1 survey at Haleakalā Observatory on 5 May 2016. Follow-up observations by the Canada-France-Hawaii Telescope at Mauna Kea Observatory discovered the second component, P/2016 J1-B, on 6 May 2016. Both asteroids are smaller than 1 kilometre (0.62 mi) in diameter, with P/2016 J1-A being roughly 0.6 km (0.37 mi) in diameter and P/2016 J1-B being roughly 0.3 km (0.19 mi) in diameter. The two components recurrently exhibit cometary activity as they approach the Sun near perihelion, suggesting that their activity is driven by sublimation of volatile compounds such as water.
