By Ron Cowen
It’s a violent world out there, and many large galaxies have the corpses to prove it. These massive galaxies, including our own Milky Way, are surrounded by streams of gas and stars, the fossil remains of dwarf galaxies that they tore apart long ago (SN: 7/7/01, p. 5: Available to subscribers at Andromeda feasts on its satellite galaxies). But examples of dwarf galaxies still in the process of giving up their material to a larger partner have proved more elusive, even though the standard theory of galaxy assembly suggests that such cannibalism is common.
Astronomers say that they now have a compelling case of a big galaxy caught in the act of eating a small fry. Some 2 billion light-years from Earth, a galaxy about as large as the Milky Way is pulling two plumes of stars from a tiny satellite galaxy, report Duncan A. Forbes of the Swinburne University of Technology in Hawthorn, Australia, and his colleagues in the Aug. 29 Science. The findings are further evidence that galaxies start out small and grow bigger over time, in part by consuming their smaller brethren, Forbes says.