Binary asteroid
A binary asteroid is a system of two asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

s orbiting their common center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

, in analogy with binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

s. 243 Ida
243 Ida
243 Ida is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Johann Palisa and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner asteroid belt. On 28...

 was the first binary asteroid to be identified when the Galileo spacecraft did a flyby in 1993. Since then numerous binary asteroids have been detected.

When both binary asteroids are similar in size, they are sometimes called "binary companions", "double asteroids" or "doublet asteroids". A good example of true binary companions is the 90 Antiope
90 Antiope
The most remarkable feature of Antiope is that it consists of two components of almost equal size , making it a truly "double" asteroid. Its binary nature was discovered on 10 August 2000 by a group of astronomers using adaptive optics at the Keck Telescope on Mauna Kea. The "secondary" is...

 system. Binary asteroids with a small satellite, called a "moonlet", have been more commonly observed (see 22 Kalliope
22 Kalliope
22 Kalliope is a large main belt M-type asteroid discovered by J. R. Hind on November 16, 1852. It is named after Calliope, the Greek Muse of epic poetry...

, 45 Eugenia
45 Eugenia
45 Eugenia is a large main-belt asteroid. It is famed as one of the first asteroids to be found to have a moon orbiting it. It is also the second known triple asteroid, after 87 Sylvia.- Discovery :...

, 87 Sylvia
87 Sylvia
87 Sylvia is one of the largest main-belt asteroids. It is a member of the Cybele group located beyond the core of the belt . Sylvia is remarkable for being the first asteroid known to possess more than one moon....

, 107 Camilla
107 Camilla
107 Camilla is one of the largest main-belt asteroids. It orbits within the Cybele Group, beyond most main-belt asteroids. It has a very dark surface and primitive carbonaceous composition. It was discovered by N. R...

, 121 Hermione
121 Hermione
121 Hermione is a very large asteroid of the dark C spectral type, orbiting in the Cybele group in the far outer asteroid belt. As a C-type, it is probably composed of carbonaceous materials. It was discovered in 1872, and it also has small asteroid moon discovered in 2002.-Discovery:Hermione was...

, 130 Elektra
130 Elektra
130 Elektra is a very large outer main-belt asteroid. It was discovered by C. H. F. Peters on February 17, 1873, and named after Electra, an avenger in Greek mythology.Its spectrum is of the G type, hence it probably has a Ceres-like composition...

, 243 Ida
243 Ida
243 Ida is an asteroid in the Koronis family of the asteroid belt. It was discovered on 29 September 1884 by Johann Palisa and named after a nymph from Greek mythology. Later telescopic observations categorized Ida as an S-type asteroid, the most numerous type in the inner asteroid belt. On 28...

, 283 Emma
283 Emma
283 Emma is a large main-belt asteroid.It was discovered by Auguste Charlois on February 8, 1889, in Nice.-Satellite:A companion for 283 Emma was detected on 14 July 2003 by W. J. Merline et al. using the Keck II telescope. It is about 12 km in diameter and is designated S/2003 1...

, 379 Huenna
379 Huenna
379 Huenna is a large Themistian asteroid. It is classified as a C-type asteroid and is probably composed of carbonaceous material.It was discovered by Auguste Charlois on January 8, 1894 in Nice...

, etc.). They are also called high size ratio binary asteroid systems.

Paired impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

s, such as the Clearwater Lakes
Clearwater Lakes
The Lac à l'Eau Claire , also called the Clearwater Lakes in English, Wiyasakami in Cree and Allait Qasigialingat by the Inuit, are a pair of circular lakes on the Canadian Shield in Quebec, Canada, near Hudson Bay.The lakes are actually a single body of water with a sprinkling of islands forming a...

 in Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, may have been formed by binary asteroids.

Several theories have been posited to explain the formation of binary-asteroid systems. Recent work suggests that most of them have a significant macro-porosity (a "rubble-pile" interior). The satellite orbiting around large main-belt asteroids such as 22 Kalliope, 45 Eugenia or 87 Sylvia could have formed by disruption of a parent body after impact or fission after an oblique impact. Trans-Neptunian binaries may have formed during the formation of the Solar System by mutual capture or three-body interaction. Near-Earth asteroids, which orbit in the inner part of the Solar System, may have split by tidal disruption after a close encounter with a terrestrial planet. A possible explanation for the relatively greater occurrence of binary asteroids near or inside of Earth's orbit was described in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

 (10 June 2008): this theory states that when solar energy (see YORP effect) spins a “rubble pile” asteroid to a sufficiently fast rate, material is thrown from the asteroid’s equator. This process also exposes fresh material at the poles of the asteroid.

See also

  • List of minor planets with moons
  • Yarkovsky-O'Keefe-Radzievskii-Paddack effect
    Yarkovsky-O'Keefe-Radzievskii-Paddack effect
    The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, or YORP effect for short, is a second-order variation on the Yarkovsky effect which changes the rotation rate of a small body . The term was coined by Dr. David P...

    (YORP effect)
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.