Binary asteroid

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Galileo image of 243 Ida, a binary asteroid
Artist's impression of the double asteroid 90 Antiope

A binary asteroid is a system of two asteroids orbiting their common barycenter, in analogy with binary stars. 243 Ida 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",[1] "double asteroids" or "doublet asteroids". Good examples of true binary companions are the 90 Antiope system and the Hermes system. Binary asteroids with a small satellite, called a "satellite", "moon", or sometimes "moonlet", have been more commonly observed (see 22 Kalliope, 45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra, 243 Ida, 283 Emma, 379 Huenna, etc.).[1] They are also called high-size-ratio or high-mass-ratio binary-asteroid systems.

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 satellites orbiting 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, most likely form by spin-up and mass shedding, likely as a result of the YORP effect. A possible explanation for the relatively greater occurrence[citation needed] of binary asteroids near or inside of Earth's orbit was described in the journal Nature (10 June 2008): this work confirms 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.[2][3]

See also[edit]


  1. ^ a b "Satellites and Companions of Minor Planets". IAU / Minor Planet Center. 2009-09-17. Retrieved 2011-01-08. 
  2. ^ Walsh, Kevin J.; Richardson, DC; Michel, P (June 2008). "Rotational breakup as the origin of small binary asteroids.". Nature 454 (7201): 188–191. Bibcode:2008Natur.454..188W. doi:10.1038/nature07078. PMID 18615078. 
  3. ^ Study Puts Solar Spin on Asteroids, their Moons & Earth Impacts Newswise, Retrieved 14 July 2008.