The newly discovered “supermassive” black hole is “among the smallest” of its kind, but it could answer some big questions.
Astronomers have discovered a “supermassive” black hole containing about 200,000 times the mass of the Sun. And this “monster” buried in the dust and gas of a dwarf galaxy could add to knowledge about the size and origin of black holes.
The discovery, presented at a virtual meeting of the American Astronomical Society on Monday, marks one of the first cases in which scientists have been able to observe a “hidden” black hole in a galaxy with only hundreds of millions of stars. And this particular dwarf galaxy is called Mrk 462.
Using NASA’s Chandra X-ray Observatory, researchers from Dartmouth College studied eight dwarf galaxies believed to contain an active supermassive black hole by searching for the extremely bright, high-energy radiation emitted by the heat from the accretion (growth) process.
The X-ray signature of the “feed” was identified. Only a black hole in Mrk 462. The “extraordinarily large density” of its high-energy radiation and other factors indicate that this particular black hole was “heavily obscured” by gas and dust clouds.
“Because buried black holes are more difficult to detect than exposed ones, finding this example could mean that there are plenty of dwarf galaxies with similar black holes,” co-author Ryan Hickox said in a NASA statement.
The discovery lends credence to theories that some supermassive black holes grow rapidly from smaller mass “stellar seeds” rather than really large in the early universe. Finding more dwarf galaxies with supermassive black holes will also bolster this idea.
The researchers note that such obscured black holes may be “missing” from previous surveys, which may indicate the presence of a much larger number of massive black holes in dwarf galaxies. These “monstrous black holes” are “hard to find” – researcher Jack Parker said – adding that those in Mrk 462 are “among the smallest” black holes of their kind.
“We cannot draw strong conclusions from a single example, but this result should encourage more comprehensive searches for black holes buried in dwarf galaxies,” Parker said.