The Milky Way Once Had a Sister Galaxy, but Andromeda Ate It
University of Michigan scientists have discovered that we once had a sister galaxy that was consumed by the Andromeda galaxy about two billion years ago. Scientists have long thought that the halo of stars surrounding Andromeda indicated that the large galaxy most likely ate smaller surrounding galaxies.
However, there was never really a way to figure out just how many galaxies it had consumed. Through the use of computer modeling, researchers are finding that most of Andromeda’s outer halo of stars was most likely made from one larger galaxy. Enter our sister galaxy, M32p. This galaxy was third in size to Andromeda and the Milky Way.
“It was shocking to realize that the Milky Way had a larger sibling, and we never knew about it.” – Eric Bell, co-author of paper in ‘Nature Astronomy’ This discovery also helps to shed light on Andromeda’s small satellite galaxy, M32.
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Scientists have never been able to figure out where it came from. Under the theory of Andromeda eating a sister galaxy, they can extrapolate that it originated as a remnant of M32p. Side note: Our galaxy will collide with Andromeda as well. But don’t stress too much. It’s destined to arrive in four billion years.
Also published on Medium.