Often referred to as the Milky Way's big sister, the nearby galaxy Andromeda is about twice as large as our own galaxy and has a similar spiral shape. A new study reveals another feature that the two have in common: Both are cannibals.
Observations of distant galaxies still forming reveal that they grow bigger by gravitationally capturing smaller galaxies that fall within their grasp. The captured material ends up in a spherical halo of matter surrounding the galaxy's disk. In our fully formed Milky Way, researchers have found several streams of gas and stars that appear to be the stretched-out remains of small galaxies gobbled up billions of years ago (SN: 4/22/0