Posted: Sun, Jan 12, 2003, 7:17 PM ET (0017 GMT)
A binary star system ejected a third star that had been orbiting the pair, the first time such an ejection has been observed, astronomers reported last week. The ejected star, T Tauri Sb, was about one-fifth the mass of the Sun and had been orbiting a pair of stars dubbed T Tauri Sa, with a combined mass twice that of the Sun, for only a few thousand years. Observations of T Tauri Sb over the last 20 years showed that the star passed close to the binary in 1995; the gravitational effect of the flyby sent the star careening away from the binary at 20 kilometers per second. Astronomers suggest that T Tauri Sb was formed in that star system but was ejected because systems of multiple stars can be unstable and chaotic. Observations over the next five years will allow astronomers to determine if the star will eventually return to the binary or has enough velocity to escape the system permanently.

Related Links:

•  AP article
•  Reuters article