Binary asteroid

[1] The mass ratio of the two components – called the "primary" and "secondary" of a binary system – is an important characteristic.

Most binary asteroids have a large mass ratio, i.e. a relatively small satellite in orbit around the main component.

Systems with one or more small moons – also called "companions" or simply "satellites" – include 87 Sylvia, 107 Camilla and 45 Eugenia (all triples), 121 Hermione, 130 Elektra (a quadruple), 22 Kalliope, 283 Emma, 379 Huenna, 243 Ida and 4337 Arecibo (in order of decreasing primary size).

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,[4] likely as a result of the YORP effect.

Binary asteroid 243 Ida with its small minor-planet moon , Dactyl , as seen by Galileo
Binary near-Earth asteroid 65803 Didymos and its moon Dimorphos imaged by the Double Asteroid Redirection Test spacecraft