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An asteroid is a minor planet—an object that is neither a true planet nor an identified comet— that orbits within the inner Solar System. They are rocky, metallic, or icy bodies with no atmosphere, classified as C-type (carbonaceous), M-type (metallic), or S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across and larger than meteoroids, to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies.
Pallas is the third-largest asteroid in the Solar System by volume and mass. It is the second asteroid to have been discovered, after Ceres, and is a likely remnant protoplanet. Like Ceres, it is believed to have a mineral composition similar to carbonaceous chondrite meteorites, though significantly less hydrated than Ceres. It is 79% the mass of Vesta and 22% the mass of Ceres, constituting an estimated 7% of the mass of the asteroid belt. Its estimated volume is equivalent to a sphere 507 to 515 kilometers in diameter, 90–95% the volume of Vesta.
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.
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. In astronomy, the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures.
In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic designations to unambiguously identify all of these objects, and at the same time give names to the most interesting objects, and where relevant, features of those objects.
Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calculated. Approximately 47% of the more than 1,100,000 known minor planets remain provisionally designated, as hundreds of thousands have been discovered in the last two decades.
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:
The Purple Mountain Observatory, also known as Zijinshan Astronomical Observatory is an astronomical observatory located on the Purple Mountain in the east of Nanjing.
Gordon John Garradd is an Australian amateur astronomer and photographer from Loomberah, New South Wales. He has discovered numerous asteroids and comets, including the hyperbolic comet C/2009 P1, and four novae in the Large Magellanic Cloud. The asteroid and Mars-crosser, 5066 Garradd, was named in his honour.
47171 Lempo, or as a binary (47171) Lempo–Hiisi (provisional designation 1999 TC36), is a trans-Neptunian object and trinary system from the Kuiper belt, located in the outermost regions of the Solar System. It was discovered on 1 October 1999, by American astronomers Eric Rubenstein and Louis-Gregory Strolger during an observing run at Kitt Peak National Observatory in Arizona, United States. Rubenstein was searching images taken by Strolger as part of their Nearby Galaxies Supernova Search project. It is classified as a plutino with a 2:3 mean-motion resonance with Neptune and is among the brighter TNOs. It reached perihelion in July 2015. This minor planet was named after Lempo from Finnish mythology.
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.
A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet. Such designation always features a leading number assigned to a body once its orbital path is sufficiently secured. The formal designation is based on the minor planet's provisional designation, which was previously assigned automatically when it had been observed for the first time. Later on, the provisional part of the formal designation may be replaced with a name. Both formal and provisional designations are overseen by the Minor Planet Center (MPC), a branch of the International Astronomical Union.
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.
According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term minor planet, but that year's meeting reclassified minor planets and comets into dwarf planets and small Solar System bodies (SSSBs). In contrast to the eight official planets of the Solar System, all minor planets fail to clear their orbital neighborhood.
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.
514107 Kaʻepaokaʻāwela, provisionally designated 2015 BZ509 and nicknamed Bee-Zed, is a small asteroid, approximately 3 km (2 mi) in diameter, in a resonant, co-orbital motion with Jupiter. It is an unusual minor planet in that its orbit is retrograde, which is opposite to the direction of most other bodies in the Solar System. It was discovered on 26 November 2014, by astronomers of the Pan-STARRS survey at Haleakala Observatory on the island of Maui, United States. Kaʻepaokaʻāwela is the first example of an asteroid in a 1:–1 resonance with any of the planets. This type of resonance had only been studied a few years before the object's discovery. One study suggests that it was an interstellar asteroid captured 4.5 billion years ago into an orbit around the Sun.
2017 YE5 is a binary pair of asteroids of approximately equal size and mass, each about 0.9 km (0.56 mi) in diameter. Classified as a near-Earth asteroid and potentially hazardous object of the Apollo group, 2017 YE5 was discovered by amateur astronomer Claudine Rinner at the Oukaïmeden Observatory on 21 December 2017. On 21 June 2018, the pair of asteroids passed within 15.5 lunar distances or approximately 6 million km (3.7 million mi) from Earth. During the close encounter, 2017 YE5 was resolved in high detail by concurrent radar observations by the Arecibo and Green Bank observatories, along with individual observations by the Goldstone Solar System Radar. 2017 YE5 is likely an extinct or dormant comet due to its distant elliptical orbit and dark red surface.
2018 VG18 is a distant trans-Neptunian object (TNO) that was discovered when it was 123 AU (18 billion km; 11 billion mi) from the Sun, more than three times the average distance between the Sun and Pluto. It was discovered on 10 November 2018 by Scott Sheppard, David Tholen, and Chad Trujillo during their search for TNOs whose orbits might be gravitationally influenced by the hypothetical Planet Nine. They announced the discovery of 2018 VG18 on 17 December 2018 and nicknamed the object "Farout" to emphasize its distance from the Sun.
2018 AG37 is a distant trans-Neptunian object and centaur that was discovered 132.2 ± 1.5 AU (19.78 ± 0.22 billion km) from the Sun, farther than any other currently observable known object in the Solar System. Imaged in January 2018 during a search for the hypothetical Planet Nine, the confirmation of this object was announced in a press release in February 2021 by astronomers Scott Sheppard, David Tholen, and Chad Trujillo. The object was nicknamed "FarFarOut" to emphasize its distance from the Sun.
References
- 1 2 "New- And Old-Style Minor Planet Designations". Minor Planet Center . Retrieved 17 December 2018.
- ↑ "Naming of Astronomical Objects". International Astronomical Union . Retrieved 17 December 2018.
