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Halley's Comet is the only known short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years. It last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061. Officially designated 1P/Halley, it is also commonly called Comet Halley, or sometimes simply Halley.
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.
Comet Encke, or Encke's Comet, is a periodic comet that completes an orbit of the Sun once every 3.3 years. Encke was first recorded by Pierre Méchain on 17 January 1786, but it was not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke. Like Halley's Comet, it is unusual in its being named after the calculator of its orbit rather than its discoverer. Like most comets, it has a very low albedo, reflecting only 4.6% of the light its nucleus receives, although comets generate a large coma and tail that can make them much more visible during their perihelion. The diameter of the nucleus of Encke's Comet is 4.8 km.
55P/Tempel–Tuttle is a retrograde periodic comet with an orbital period of 33 years. It fits the classical definition of a Halley-type comet with a period of between 20 and 200 years. It was independently discovered by Wilhelm Tempel on December 19, 1865, and by Horace Parnell Tuttle on January 6, 1866.
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.
Damocloids are a class of minor planets such as 5335 Damocles and 1996 PW that have Halley-type or long-period highly eccentric orbits typical of periodic comets such as Halley's Comet, but without showing a cometary coma or tail. David Jewitt defines a damocloid as an object with a Jupiter Tisserand invariant (TJ) of 2 or less, while Akimasa Nakamura defines this group with the following orbital elements:
39P/Oterma is a currently inactive periodic comet with an orbital period of nearly 20 years that stays outside the orbit of Jupiter. The nucleus has a diameter around 4–5 km. It was last observed in August 2021 and came to perihelion in July 2023 while 1.2 AU from Jupiter. It will finish the modest approach to Jupiter in January 2025 and will next come to perihelion in July 2042 at distance of 5.9 AU from the Sun. Opposition has occurred on 11 November 2023.
73P/Schwassmann–Wachmann, also known as Schwassmann–Wachmann 3 or SW3 for short, is a periodic comet that has a 5.4 year orbital period and that has been actively disintegrating since 1995. When it came to perihelion in March 2017, fragment 73P-BT was separating from the main fragment 73P-C. Fragments 73P-BU and 73P-BV were detected in July 2022. The main comet came to perihelion on 25 August 2022, when the comet was 0.97 AU from the Sun and 1 AU from Earth. It will be less than 80 degrees from the Sun from 25 May 2022 until August 2023. On 3 April 2025 it will make a modest approach of 0.3 AU to Jupiter. 73P will next come to perihelion on 23 December 2027 when it will be 0.92 AU from the Sun and on the far side of the Sun 1.9 AU from Earth.
166P/NEAT is a periodic comet and centaur in the outer Solar System. It was discovered by the Near Earth Asteroid Tracking (NEAT) project in 2001 and initially classified a comet with provisional designation P/2001 T4 (NEAT), as it was apparent from the discovery observations that the body exhibited a cometary coma. It is one of few known bodies with centaur-like orbits that display a coma, along with 60558 Echeclus, 2060 Chiron, 165P/LINEAR and 167P/CINEOS. It is also one of the reddest centaurs.
118401 LINEAR (provisional designation 1999 RE70, comet designation 176P/LINEAR) is an active asteroid and main-belt comet that was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) 1-metre telescopes in Socorro, New Mexico on September 7, 1999. (118401) LINEAR was discovered to be cometary on November 26, 2005, by Henry H. Hsieh and David C. Jewitt as part of the Hawaii Trails project using the Gemini North 8-m telescope on Mauna Kea and was confirmed by the University of Hawaii's 2.2-m (88-in) telescope on December 24–27, 2005, and Gemini on December 29, 2005. Observations using the Spitzer Space Telescope have resulted in an estimate of 4.0±0.4 km for the diameter of (118401) LINEAR.
Comet 322P/SOHO, also designated P/1999 R1, P/2003 R5, P/2007 R5, and P/2011 R4, is the first periodic comet to be discovered using the automated telescopes of the SOHO spacecraft, and second to be given a numbered designation, after 321P/SOHO. JPL Horizons next predicts 322P to come to perihelion on 21 August 2023 at around apparent magnitude 6 and only 3 degrees from the Sun. At perihelion it is six times closer to the Sun than the planet Mercury is at perihelion.
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.
D/1770 L1, popularly known as Lexell's Comet after its orbit computer Anders Johan Lexell, was a comet discovered by astronomer Charles Messier in June 1770. It is notable for having passed closer to Earth than any other comet in recorded history, approaching to a distance of only 0.015 astronomical units, or six times the distance from the Earth to the Moon. The comet has not been seen since 1770 and is considered a lost comet.
An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface layer.
82P/Gehrels is a periodic comet that was discovered on October 27, 1975, by Tom Gehrels at the Palomar Mountain Observatory in California having a faint nuclear brightness of magnitude 17.
The Great Southern Comet of 1887, or C/1887 B1 using its International Astronomical Union (IAU) designation, was a bright comet seen from the Southern Hemisphere during January 1887. Later calculations indicated it to be part of the Kreutz Sungrazing group. It came to perihelion on 11 January 1877 at a distance of 0.00483 AU (723 thousand km) with a velocity of 606.1 km/s. Since the Sun has a radius of 696000 km, the comet passed about 27000 km from the surface of the Sun.
In observational astronomy, the observation arc of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly used in the discovery and tracking of asteroids and comets. Arc length has the greatest influence on the accuracy of an orbit. The number, spacing of intermediate observations, and timestamps have a lesser effect.
In planetary science, the term unusual minor planet, or unusual object, is used for a minor planet that possesses an unusual physical or orbital characteristic. For the Minor Planet Center (MPC), which operates under the auspices of the International Astronomical Union, any non-classical main-belt asteroid, which account for the vast majority of all minor planets, is an unusual minor planet. These include the near-Earth objects and Trojans as well as the distant minor planets such as centaurs and trans-Neptunian objects. In a narrower sense, the term is used for a group of bodies – including main-belt asteroids, Mars-crossers, centaurs and otherwise non-classifiable minor planets – that show a high orbital eccentricity, typically above 0.5 and/or a perihelion of less than 6 AU. Similarly, an unusual asteroid (UA) is an inner Solar System object with a high eccentricity and/or inclination but with a perihelion larger than 1.3 AU, which does exclude the near-Earth objects.
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.
2022 AP7 is a kilometer-sized Apollo asteroid and potentially hazardous object orbiting between Venus and Jupiter. It was discovered on 13 January 2022 by Scott Sheppard at Cerro Tololo Observatory. Based on its absolute magnitude (H), 2022 AP7 is likely the largest potentially hazardous object identified in the eight years prior to its 2022 discovery.
References
- 1 2 3 4 5 6 7 Abell, Paul A.; Fernández, Yanga R.; Pravec, Petr; French, Linda M.; Farnham, Tony L.; Gaffey, Michael J.; Hardersen, Paul S.; Kušnirák, Peter; Šarounová, Lenka; Sheppard, Scott S. (2003). "Physical Characteristics of Asteroid-like Comet Nucleus C/2001 OG108 (LONEOS)". 34th Annual Lunar and Planetary Science Conference: 1253. Bibcode:2003LPI....34.1253A.
- 1 2 French, Linda M. (2002). "Pre-Activity BVRI Colors of High-Inclination Comet C/2001 OG108 (LONEOS)". American Astronomical Society, DPS Meeting No. 34, #16.01. 34: 868. Bibcode:2002DPS....34.1601F.
- 1 2 3 4 5 6 7 8 9 "JPL Small-Body Database Browser: C/2001 OG108 (LONEOS)" (last observation: 2002-07-03; arc: 340 days). Jet Propulsion Laboratory. Archived from the original on 24 July 2020. Retrieved 18 May 2011.
(Close approach uncertainty: (MaxDist of 0.434) – (MinDist of 0.408) * 149597870.7 = 3.9 million km) - 1 2 "Horizons Batch for C/2001 OG108 (LONEOS) on 2050-Jun-07" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons . Retrieved 20 January 2023. (JPL#42/Soln.date: 2021-Apr-15)
- ↑ "JPL Small-Body Database Search Engine: comets and q < 1 (au) and period < 200 (years)". JPL Solar System Dynamics. Retrieved 24 July 2020.
- ↑ "Horizons Batch for 2147-Mar-23 Earth Approach". JPL Horizons. Archived from the original on 20 January 2023. Retrieved 20 January 2023.
