The dynamics within the core of this neighboring galaxy may be more common than we think. Our own Milky Way apparently has even younger stars close to its own black hole. It seems unlikely that only the closest two big galaxies should have this odd activity. So this behavior may not be the exception but the rule. And we have found other galaxies that have a double nucleus.

The blue stars in the disk are so short-lived that it is unlikely in the long 12-billion-year history of Andromeda that such a short-lived disk would appear now. That's why we think that the mechanism that formed this disk of stars probably formed other stellar disks in the past and will trigger them again in the future. We still don't know, however, how such a disk could form in the first place. It still remains an enigma.

The blue stars in the disk are so short-lived that it is unlikely in the long 12-billion-year history of Andromeda that such a short-lived disk would appear now. We think that the mechanism that formed this disk of stars probably formed other stellar disks in the past and will trigger them again in the future. We still don't know, however, how such a disk could form in the first place. It still remains an enigma.

Seeing these stars is like watching a magician pulling a rabbit out of a hat. You know it happened but you don't know how it happened.

Some of the stars in this Milky Way companion have been seen with telescopes for centuries. But because the galaxy is so close, its stars are spread over a huge swath of the sky, and they always used to be lost in the sea of more numerous Milky Way stars. This galaxy is so big, we couldn't see it before.

With so much irregular structure in the outer Galaxy, it looks as though the Milky Way is still growing, by cannibalizing smaller galaxies that fall into it.