In astronomy, the term contact binary refers to two astronomical bodies that are so close that they touch each other.
Normally, the term may refer either to stars (see Binary star) or to asteroids.


In the study of asteroids, a contact binary is caused when two asteroids gravitate toward each other until they touch, forming an oddly-shaped single body. Asteroids suspected of being contact binaries include the unusually elongated 624 Hektor and the bilobated 216 Kleopatra and 4769 Castalia. 25143 Itokawa, recently photographed by the Hayabusa probe, also appears to be a contact binary which has resulted in an elongated, bent body.

Stars: Common envelope binaries

See also