Tour: "Mini" Monster Black Hole Could Hold Clues to Giant's Growth

The discovery of a supermassive black hole in a relatively small galaxy could help astronomers unravel the mystery surrounding how the very biggest black holes grow.

Researchers used NASA's Chandra X-ray Observatory to identify a black hole containing about 200,000 times the mass of the Sun buried in gas and dust in the galaxy named Markarian 462.

Markarian 462 contains only several hundred million stars, making it a dwarf galaxy. By contrast, our Milky Way is home to a few hundred billion stars. This is one of the first times that a heavily buried, or "obscured," supermassive black hole has been found in a dwarf galaxy.

In larger galaxies astronomers often find black holes by looking for the rapid motions of stars in the centers of galaxies. However, dwarf galaxies are too small and dim for most current instruments to detect this. Another technique is to search for the signatures of growing black holes, such as gas being heated up to millions of degrees and glowing in X-rays as it falls towards a black hole.

The researchers in this study used Chandra to look at eight dwarf galaxies that had previously shown hints of black hole growth from optical data gathered by the Sloan Digital Sky Survey. Of those eight, only Markarian 462 showed the X-ray signature of a growing black hole.

Astronomers are trying to figure out the fraction of smaller galaxies that contain supermassive black holes because that could help determine an important piece of black hole history. A large fraction of dwarf galaxies with supermassive black holes favors the idea that small black hole seeds from the earliest generation of stars grew astonishingly quickly to form the billion solar mass objects in the early universe. A smaller fraction would tip the scales to favor the idea that black holes began life weighing tens of thousands of Suns.

While scientists can't make strong conclusions from one example, they hope this result will encourage more extensive searches for buried black holes in dwarf galaxies.