Sagittarius A*, the Milky Way Galaxy's central black hole
An X-ray image (left) of Sagittarius A*, the Milky Way Galaxy's central black hole, suggests that stars may be able to form in a way unknown to scientists.
Researchers have traditionally believed that tidal forces from the black hole would tear apart the gas clouds from which stars form. But it seems that the gravity of a dense disk of gas around Sagittarius A* offsets the forces. And the tension between the tidal forces and the gravity of the disk has led to the creation of a much higher proportion of massive stars than normal (as seen in the illustration on the right).
Another theory has it that the massive stars formed elsewhere and moved toward the black hole. But such stars would have brought many low-mass stars with them, and NASA's Chandra X-ray Observatory hasn't found any such low-mass stars. The conclusion then, is that the stars formed where they are.