Supermassive Black Hole Found in Dwarf Galaxy

Jan 12, 2022 | AAS, Daily Space, Galaxies, Supermassive Black Holes

IMAGE: The optical image is from the Pan-STARRS telescope in Hawaii, with several galaxies from the HCG068 galaxy group on the left-hand side and the much smaller Mrk 462 to the lower right. Astronomers will continue to try to determine the percentage of dwarf galaxies that have supermassive black holes. CREDIT: X-ray: NASA/CXC/Dartmouth Coll./J. Parker & R. Hickox; Optical/IR: Pan-STARRS

A new image released by the Chandra X-ray Observatory and presented at an AAS press conference shows the detection of X-rays coming from dwarf galaxy Mrk 462. These X-rays reveal the existence of a supermassive black hole, about 200,000 times the mass of the Sun, hiding within the dwarf galaxy, which only contains several hundred million stars compared to the hundreds of billions of stars in our own Milky Way galaxy.

As mentioned in our previous story, finding black holes in dwarf galaxies is difficult, and this is one of the few times we have managed to detect one. Instead of using spectral lines, Chandra looks for X-rays, which are emitted when gas is superheated and glows brightly as it falls in toward the black hole. And Chandra looked at eight dwarf galaxies in this recent study; Mrk 462 was the only one that had the X-ray signatures of a black hole. Co-author Ryan Hickox notes: 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. This is important because it could help address a major question in astrophysics: How did black holes get so big so early in the universe?

Black holes have been found that are a billion times the mass of the Sun and existed when the universe wasn’t even a billion years old. One school of thought was that massive stars collapsed early on and formed black holes that were about 100 solar masses, and then those black holes somehow grew really quickly. Another possibility is that there were many black holes around tens of thousands of solar masses all over the universe created when huge clouds of gas and dust collapsed.

As we get a better understanding of what fraction of dwarf galaxies have supermassive black holes, we should be able to pick one of those two options as the correct one. As the press release states: 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.

However, one sample is not enough to determine any sort of conclusion.

More Information

CXO press release

CXO photo release

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