The Milky Way Had a Big Sibling Long Ago — And Andromeda Ate It

Andromeda Galaxie(M31) Bild: nasa/PD
The Milky Way had a previously unknown big sibling that was torn apart by the neighboring Andromeda galaxy long ago, a new study suggests.

By Mike Wall |

Andromeda and the Milky Way are the two largest members of the Local Group, a collection of more than 50 galaxies packed into a dumbbell-shaped region of space about 10 million light-years across. Andromeda was not kind to the onetime third-biggest member of this family, devouring it about 2 billion years ago, according to the new research.

„Astronomers have been studying the Local Group — the Milky Way, Andromeda and their companions — for so long,“ study co-author Eric Bell, a professor of astronomy at the University of Michigan (UM), said in a statement. „It was shocking to realize that the Milky Way had a large sibling, and we never knew about it.“ [When Galaxies Collide: Photos of Great Galactic Crashes]

Andromeda, also known as M31, is a prolific cannibal; the huge spiral galaxy is thought to have shredded hundreds of its smaller kin over the eons. The number and complexity of these mergers makes it tough to tease out the details of any particular one — but Bell and study lead author Richard D’Souza, a postdoctoral researcher at UM, were able to do just that.

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