For those of you worried about the nearby Andromeda galaxy colliding with our own Milky Way in the distant future, here’s a little perspective: Turns out our spiral galaxy is still reeling from a hard knock it suffered as recently as 100 million years ago -- but it’s likely to recover just as quickly, say researchers at the Fermi National Accelerator Laboratory in Batavia, Ill.
Fermilab scientists looked at about 300,000 stars cataloged by the Sloan Digital Sky Survey – which has mapped a full 35% of the sky using an optical telescope in New Mexico – and noticed something strange: Some nearby stars north and south of the Milky Way’s plane were out of sync relative to one another.
As these stars spin around the Milky Way’s flattened disc at about 220 kilometers per second, they also bob up and down at roughly 20 to 30 kilometers per second. Since they’re doing about the same thing, the distribution and motion of these stars along the north-south divide should be fairly symmetric.
But to the scientists’ surprise, neither the stars’ positions nor their motions were as regular as they expected. At first, they thought it might have to do with interference from all the interstellar dust hanging out between the stars, or something to do with how they selected which stars to study.