The Andromeda Galaxy is a big, splashy spiral galaxy, the largest one nearby (less than 3 million light years away - that's close as galaxies go). Like every major galaxy, it has a supermassive black hole in its core -- specifically, Andromeda's has a hefty 100 million times the mass of the Sun, making it far larger than our own Milky Way's 4 million mass central black hole.
You'd think such a place would be anathema for anything else, but in fact there is not one but two populations of stars there! Seen in this Hubble image, there is a large cluster of bright blue stars surrounding the galaxy's black hole, which apparently formed there about 200 million years ago.
Surrounding that is a ring of older, redder stars, appearing to give Andromeda two nuclei. Stars orbiting black holes are not too surprising - we see that in our own galaxy - but it's not at all clear how those blue stars could've formed so close to that monster in the middle. Hubble observations like this one will hopefully help us understand and eventually solve that mystery.Original SourceCredit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)/T. Rector and B. Wolpa, NOAO