A young star moving at high velocity, perhaps hundreds of kilometres per second, suggesting that it has been ejected by some violent event from its birthplace. Such stars were probably once part of a binary, but were ejected either when their companion exploded as a supernova, or else through a close encounter with another binary. Examples of the first type are Zeta Ophiuchi and the pulsar PSR J1932+1059, resulting from a binary disrupted by a supernova about a million years ago. AE Aurigae and Mu Columbae, moving away from the Trapezium region of Orion in opposite directions at around 100 km/s, are thought to result from an encounter between two binaries 2.5 million years ago; their former partners now constitute Iota Orionis, a binary with a highly eccentric orbit.