Milky Way's 3rd Sibling Galaxy? Andromeda Ate It

The Milky Way had a sibling besides neighboring galaxy Andromeda, but in an act of galactic cannibalism Andromeda ate it, a new study theorizes.

About two billion years ago, an expansive collection of galaxies called the Local Group were dominated by three of its largest members – Andromeda, the Milky Way and a third massive galaxy which was devoured by its spiraling sibling, Space.com reported.

Andromeda, also known as M31, seems to be a prolific predator and researchers believe the galaxy has shredded many companion galaxies in the past.

The remnants of these smaller cannibalized galaxies are what causes the nearly invisible halo of stars to surround a galaxy like Andromeda and, knowing this, scientists thought it would be hard to learn much about any single one of the consumed companions, but they were in luck.

Using computer models, Richard D’Souza and Eric Bell of the University of Michigan’s Department of Astronomy were able to piece together evidence of the large, decimated galaxy M32p.

"Astronomers have been studying the Local Group — the Milky Way, Andromeda and their companions — for so long. It was shocking to realize that the Milky Way had a large sibling, and we never knew about it," said study co-author Bell.

M32p was at least 20 times bigger than any other galaxy to merge with the Milky Way, making it the third largest galaxy in the Local Group, and it’s not completely gone.

Researchers believe that Andromeda's satellite galaxy M32 is actually the surviving center of the Milky Way’s long-lost sibling.

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