Credit: X-ray: NASA/CXC/Dartmouth.
Figuring out how the biggest black holes grow could be aided by the discovery of a supermassive black hole.
Researchers used NASA's Chandra X-ray Observatory to identify a black hole that was 200,000 times the mass of the Sun.
It is a dwarf galaxy with only a few hundred million stars. Our Milky Way has a few hundred billion stars. This is the first time that a super massive black hole has been found in a dwarf galaxy.
The black hole in Mrk 462 is among the smallest of the monster black holes, according to a study led by Jack and Ryan Hickox from the University of New Hampshire. Black holes like this are hard to find.
Black holes can be found in larger galaxies by looking for stars that move quickly. Most current instruments can't detect dwarf galaxies. Gas being heated up to millions of degrees and glowing in X-rays as it falls towards a black hole are some of the signatures of growing black holes.
The researchers used Chandra to look at eight dwarf galaxies that had previously shown signs of black hole growth. The X-ray signature of a growing black hole was only shown by Mrk .
The large intensity of high energy X-rays compared to low energy X-rays, along with comparisons to data at other wavelengths, indicates that the Mrk is heavily obscured by gas.
"Because buried black holes are even harder to detect than exposed ones, finding this example might mean there are a lot more dwarf galaxies out there with similar black holes," said Hickox. It could help answer a major question in astrophysics, how black holes get so big so early in the universe.
Black holes can grow to a billion solar mass by the time the universe is a billion years old, a small fraction of its current age. One idea is that these objects were created when stars collapsed to form black holes that weighed less than the mass of the Sun. It's difficult to explain how they could pack on weight quickly enough to reach the sizes seen in the early universe.
An alternative explanation is that the universe was created by the collapse of huge clouds of gas and dust.
The idea that small black hole seeds from the earliest generation of stars formed the billion solar mass objects in the early universe is supported by a large fraction of dwarf galaxies. The idea that black holes weighed tens of thousands of Suns was supported by a smaller fraction.
It is not expected that a large fraction of dwarf galaxies would contain supermassive black holes because the conditions needed for a direct collapse from a giant cloud to a medium-sized black hole should be rare. Black holes are expected in every galaxy.
"We can't make strong conclusions from one example, but this result should encourage much more extensive searches for buried black holes in dwarf galaxies," he said. We're excited about what we learn.
The results were scheduled to be presented at the American Astronomical Society meeting in Salt Lake City, but instead they were part of a virtual press briefing.
The dwarf galaxy Mrk 462 is a mini monster black hole and could hold clues to giant's growth.
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