Up To 2,000 Black Holes May Be On Perimeter Of Our Galaxy

Space scientists from the University of California have used a computer model to determine that our galaxy may contain anywhere from 70 to 2,000 black holes existing along its outer edges.

Valery Rashkov and Piero Madau's computer model mimics what they believe occurred when galaxies were in formative stages. The model starts with the idea that there is a subgalactic building block called a "seed" black hole that was in the center of old galaxies.  As the Universe aged, galaxies crashed into one another, merging as they did so and causing their central black holes to merge as well.

But the computer simulations show that not all galaxies merged neatly. The researchers suggest that gravitational waves created by colliding galaxies ejected smaller black holes form the merger, shooting the singularities to the outer perimeter of the galaxy.

The simulations show that these ejections occurred less than 20 percent of the time, according to Phys.org. As a result of all the intergalactic merging and ejecting, our Milky Way galaxy should have at least 70, but as many as 2,000 intermediate mass black holes in its halo, the researchers suggest.

A spiral galaxy like the Mikly Way contains three basic parts, the star-dense nucleus, the "sprial" arms and the halo.

The simulation also provides support for our understanding of the formation of supermassive black holes, as when neither of the seed black holes were ejected from a merging galaxy, the two seed black holes merged as well. This can happen many times, leading to the creation of black holes with unfathomable mass.

It will be difficult for the researchers to prove that their model is correct as black holes cannot be seen directly, but their presence may be calcualted by taking gravitational forces surrounding them.

Their paper has been uploaded to Cornell University's preprint server arXiv and has been submitted to The Astrophysical Journal.