The previously undiscovered black holes provide an important link that sheds light on the way black holes grow. Even more odd, these new black holes were found in the cores of glittering, "beehive" swarms of stars — called globular star clusters — that orbit our Milky Way and other galaxies.
The new findings promise a better understanding of how galaxies and globular clusters first formed billions of years ago. Globular star clusters contain the oldest stars in the universe. If globulars have black holes now, then globulars most likely had black holes when they originally formed. The new results indicate that the very sedate, elderly environments of globular clusters house these exotic objects, quite unlike the violent cores of some galaxies.
These findings may be telling us something very deep about the formation of star clusters and black holes in the early universe, says Roeland Van Der Marel of the Space Telescope Science Institute in Baltimore. "Black holes are even more common in the universe than previously thought."
Not only will we learn about the formation of the black holes, but these new data from Hubble help us connect globular clusters to galaxies, providing information on one of the most important unsolved problems in astronomy today: how galaxy structure forms in the universe, adds Michael Rich of the University of California, Los Angeles (UCLA).
These intermediate-mass black holes may provide a link between stellar-mass and supermassive black holes. This link is important because it may hold the clue to how supermassive black holes form in galaxies. This is reinforced by the uncanny fact found by these investigations that a black hole's mass is proportional to the mass of the stellar environment it inhabits. Supermassive black holes found by Hubble in the centers of galaxies represent about 0.5 percent of the galaxies' mass. Amazingly, the black holes now found in star clusters, which are 10,000 times less massive than a galaxy, also obey this trend. It appears that there is some yet-to-be-discovered underlying process that ties a black hole to its host in a fundamental way. Nature is providing a big clue as to how these systems and their black holes form.