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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 they cross or have crossed the orbits of the giant planets; 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.
Comet 29P/Schwassmann–Wachmann, also known as Schwassmann–Wachmann 1, was discovered on November 15, 1927, by Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Bergedorf, Germany. It was discovered photographically, when the comet was in outburst and the magnitude was about 13. Precovery images of the comet from March 4, 1902, were found in 1931 and showed the comet at 12th magnitude.
The Panoramic Survey Telescope and Rapid Response System located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is surveying the sky for moving or variable objects on a continual basis, and also producing accurate astrometry and photometry of already-detected objects. In January 2019 the second Pan-STARRS data release was announced. At 1.6 petabytes, it is the largest volume of astronomical data ever released.
60558 Echeclus is a centaur, approximately 84 kilometers (52 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.
(523731) 2014 OK394, also known as 1995 SN55, is a trans-Neptunian object that orbits in the outer Solar System beyond the orbit of Neptune. First observed as 1995 SN55 by Spacewatch on 20 September 1995, it was a lost minor planet with an insufficiently defined orbit with only 36 days of observations. On 8 October 2010, it was rediscovered by the Pan-STARRS 1 survey and later announced as 2014 OK394 in July 2016. It was not until November 2020 when amateur astronomers S. Deen and K. Ly identified 2014 OK394 and 1995 SN55 as the same object. This identification was confirmed and announced by the Minor Planet Center in January 2021.
(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.
C/2011 L4 (PanSTARRS), also known as Comet PANSTARRS, is a non-periodic comet discovered in June 2011 that became visible to the naked eye when it was near perihelion in March 2013. It was discovered using the Pan-STARRS telescope located near the summit of Haleakalā, on the island of Maui in Hawaii. Comet C/2011 L4 probably took millions of years to come from the Oort cloud. After leaving the planetary region of the Solar System, the post-perihelion orbital period is estimated to be roughly 107000 years. Dust and gas production suggests the comet nucleus is roughly 1 kilometer (0.62 mi) in diameter, while based on the absolute nuclear magnitude and a geometric albedo of 0.04 the diameter of the nucleus is over 2.4 kilometers (1.5 mi). A method based on coma magnitude decay fuction estimated the effective radius at 2.317 ± 0.190 km.
C/2015 ER61 (PanSTARRS) is a comet and inner Oort cloud object. When classified as a minor planet, it had the fourth-largest aphelion of any known minor planet in the Solar System, after 2005 VX3, 2012 DR30, and 2013 BL76. It additionally had the most eccentric orbit of any known minor planet, with its distance from the Sun varying by about 99.9% during the course of its orbit, followed by 2005 VX3 with an eccentricity of 0.9973. On 30 January 2016, it was classified as a comet when it was 5.7 AU from the Sun. It comes close to Jupiter, and a close approach in the past threw it on the distant orbit it is on now.
C/2017 K2 (PanSTARRS) is an Oort cloud comet with an inbound hyperbolic orbit, discovered in May 2017 at a distance beyond the orbit of Saturn when it was 16 AU (2.4 billion km) from the Sun. Precovery images from 2013 were located by July. It had been in the constellation of Draco from July 2007 until August 2020. As of June 2022, the 3-sigma uncertainty in the current distance of the comet from the Sun is ±6000 km.
A hyperbolic asteroid is any sort of asteroid or non-cometary astronomical object observed to have an orbit not bound to the Sun and will have an orbital eccentricity greater than 1 when near perihelion. Unlike hyperbolic comets, they have not been seen out-gassing light elements, and therefore have no cometary coma. Most of these objects will only be weakly hyperbolic and will not be of interstellar origin.
C/2017 U7 (PanSTARRS) is a hyperbolic comet, first observed on 29 October 2017 by astronomers of the Pan-STARRS facility at Haleakala Observatory, Hawaii, United States when the object was 7.8 AU (1.2 billion km) from the Sun. Despite being discovered only 10 days after interstellar asteroid 1I/'Oumuamua, it was not announced until March 2018 as its orbit is not strongly hyperbolic beyond most Oort Cloud comets. Based on the absolute magnitude of 10.6, it may measure tens of kilometers in diameter. As of August 2018, there is only 1 hyperbolic asteroid known, ʻOumuamua, but hundreds of hyperbolic comets are known.
A temporary satellite is an object which has been captured by the gravitational field of a planet and thus has become the planet's natural satellite, but, unlike irregular moons of the larger outer planets of the Solar System, will eventually either leave its orbit around the planet or collide with the planet. The only observed examples are 2006 RH120, a temporary satellite of Earth for twelve months from July 2006 to July 2007, and 2020 CD3, which was discovered in 2020. Some defunct space probes or rockets have also been observed on temporary satellite orbits.
C/2018 F4 (PanSTARRS) is a hyperbolic comet. It was discovered on 17 March 2018 when it was beyond the orbit of Jupiter, 6.4 AU (960 million km) from the Sun. It was quite far from the Sun and turned out to simply be an asteroidal object that was discovered before cometary activity was noticeable. As perihelion is inside the orbit of Jupiter, this object should become more active. In April 2018 it was determined to be a hyperbolic comet. Given that the incoming velocity was similar to that of an Oort cloud object, we can very confidently say that it is not of interstellar origin. C/2018 F4 fragmented around August 2020.
(495603) 2015 AM281, provisional designation 2015 AM281, is a resonant trans-Neptunian object in the outermost region of the Solar System, guesstimated at approximately 470 kilometers (290 miles) in diameter. It was discovered on 13 March 2010, by astronomers with the Pan-STARRS survey at Haleakala Observatory, Hawaii, United States.
2I/Borisov, originally designated C/2019 Q4 (Borisov), is the first observed rogue comet and the second observed interstellar interloper after ʻOumuamua. It was discovered by the Crimean amateur astronomer and telescope maker Gennadiy Borisov on 29 August 2019 UTC.
Chimera is a NASA mission concept to orbit and explore 29P/Schwassmann-Wachmann 1 (SW1), an active, outbursting small icy body in the outer Solar System. The concept was developed in response to the 2019 NASA call for potential missions in the Discovery-class, and it would have been the first spacecraft encounter with a Centaur and the first orbital exploration of a small body in the outer Solar System. The Chimera proposal was ranked in the first tier of submissions, but was not selected for further development for the programmatic reason of maintaining scientific balance.
C/2017 T2 (PanSTARRS) is an Oort cloud comet discovered on 2 October 2017 when it was 9.2 AU (1.38 billion km) from the Sun. The closest approach to Earth was on 28 December 2019 at a distance of 1.52 AU (227 million km). It came to perihelion on 4 May 2020 when it was safe from disintegration at 1.6 AU from the Sun.
C/2014 OG392 (PanSTARRS) is a comet discovered as a centaur on 28 July 2014 when it was 11.5 AU (1.72 billion km) from the Sun and had an apparent magnitude of 21. The comet was relatively easier to detect at this distance because the nucleus is estimated to be 20 km in diameter.
C/2014 UN271 (Bernardinelli–Bernstein), simply known as C/2014 UN271 or Comet Bernardinelli–Bernstein (nicknamed BB), is a large Oort cloud comet discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey. When first imaged in October 2014, the object was 29 AU (4.3 billion km; 2.7 billion mi) from the Sun, almost as far as Neptune's orbit and the greatest distance at which a comet has been discovered. With a nucleus diameter of at least 120 km (75 mi), it is the largest Oort cloud comet known. It is approaching the Sun and will reach its perihelion of 10.9 AU (just outside of Saturn's orbit) in January 2031. It will not be visible to the naked eye because it will not enter the inner Solar System.
C/2021 O3 (PanSTARRS) is perhaps an Oort cloud comet, discovered on 26 July 2021 by the Pan-STARRS sky survey. It came to perihelion on 21 April 2022 at 0.287 AU (42.9 million km). from the Sun.
References
- 1 2 3 "JPL Small-Body Database Browser: 2020 MK4" (2020-06-06 last obs.). Jet Propulsion Laboratory . Retrieved 5 April 2021.
- ↑ "Orbit Fit and Astrometric record for 20MK4". Southwest Research Institute . Retrieved 11 August 2021. The Deep Ecliptic Survey Object Classifications
- 1 2 3 4 5 6 de la Fuente Marcos, C.; de la Fuente Marcos, R.; Licandro, J.; Serra-Ricart, M.; Martino, S.; de Leon, J.; Chaudry, F.; Alarcón, M. R. (13 May 2021). "The active centaur 2020 MK4". Astronomy & Astrophysics . 649 (1): A85 (15 pages). arXiv: 2104.01668 . Bibcode:2021A&A...649A..85D. doi:10.1051/0004-6361/202039117. S2CID 233024896.
- ↑ "MPEC 2020-N36: 2020 MK4". Minor Planet Electronic Circular. Minor Planet Center. 11 July 2020. Retrieved 5 April 2021.
- ↑ "2020 MK4 belatedly confirmed outburst". Minor Planet Mailing List . Retrieved 6 April 2021.
- ↑ "MPEC 2022-W16: 2020 MK4". Minor Planet Electronic Circular. Minor Planet Center. 16 November 2022. Retrieved 20 November 2022.
- ↑ "MPEC 2022-W78 : COMET P/2020 MK4 (PANSTARRS)". Minor Planet Electronic Circular. Minor Planet Center. 20 November 2022. Retrieved 20 November 2022.
- ↑ Green, Daniel W. E. (20 November 2022). "COMET P/2020 MK_4 (PANSTARRS)". Central Bureau Electronic Telegrams. Central Bureau for Astronomical Telegrams. Retrieved 20 November 2022.
- ↑ Horner, J.; Evans, N.W.; Bailey, M. E. (2004). "Simulations of the Population of Centaurs I: The Bulk Statistics". Monthly Notices of the Royal Astronomical Society . 354 (3): 798. arXiv: astro-ph/0407400 . Bibcode:2004MNRAS.354..798H. doi:10.1111/j.1365-2966.2004.08240.x. S2CID 16002759.