Scientists just found that the Andromeda Galaxy isn't making as many new stars as it used to.
Using Hubble data, they saw star formation drop sharply from about one sun's worth of gas and dust into newborn stars each year around 500 million years ago, to about one-half of that about 40 million years ago, and to just one-fifth today.
The likely culprit? Its smaller neighbor, M32.
Andromeda slowdown strongest on M32 side
The slowdown is most obvious on the side of the Andromeda Galaxy facing M32, which sits just 16,000 light-years away.
Researchers think M32 may be the rump core of a spiral galaxy that lost its arms, possibly after a collision with the Andromeda Galaxy long ago.
While scientists aren't totally sure how it happened yet, the Nancy Grace Roman Space Telescope should help clear things up soon.