Sorry Goldilocks, Black Holes Come in Small and Large

Aug. 20, 2008 -- There are massive black holes, like the one at the center of the Milky Way galaxy, and petite black holes, but few, if any contenders in the middle-class division, if indeed that population exists.

Until this week, scientists believed their best chance for finding a mid-size black hole would be in a globular cluster, a densely packed region of stars that often live inside or alongside larger, more spacious galaxies.

After analyzing tantalizing black hole signatures coming from a globular cluster roughly 50 million light-years away, a team of researchers headed by Michigan State University's Stephen Zepf has a suggestion: Look elsewhere.

The cluster, known as RZ2109, does indeed bear telltale signs of a black hole, but it's a small one, with about 10 times the mass of our sun.

Black holes are areas of space where the gravitational forces of matter are so strong that not even photons of light can escape the clutch.

"We know there are these black holes in the centers of the galaxies, and we know the bigger the black hole, the bigger the galaxy," Zepf told Discovery News.

"Since the globular clusters are smaller groups of stars, we thought the black holes could start smaller and then build up," he added.