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Astronomers find a teeny-tiny supermassive black hole

At the core of the dwarf galaxy RGG 118, University of Michigan astronomers have found the smallest supermassive black hole ever discovered. (Vivienne Baldassare/University of Michigan)
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It's the biggest oxymoron ever: An itty-bitty supermassive black hole. The smallest supermassive black hole ever found in the center of a galaxy, as a matter of fact.

This is admittedly confusing. A tiny supermassive black hole? Why bother calling it supermassive, then? Why bother with adjectives? Have words lost all meaning?

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Black holes come in at least two flavors: stellar and supermassive. A stellar black hole forms when a huge star collapses in on itself, and those black holes will be just a few times more massive than our sun. Supermassive black holes sit at the center of most galaxies, and astronomers are still figuring out how exactly they form.

Supermassive black holes are typically at least 100,000 times as massive as the sun. This new guy, described in a study published Tuesday in Astrophysical Journal Letters, is just 50,000 times as massive as the sun -- and 100 times less massive than the black hole at the center of our own galaxy.

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The black hole sits in the center of a dwarf galaxy some 340 million light years from Earth. Because the galaxy and its black hole are so small, researchers are hoping they might share similarities with young galaxies.

"These little galaxies can serve as analogs to galaxies in the earlier universe," first author Vivienne Baldassare, a grad student at the University of Michigan, said in a statement. "For galaxies like our Milky Way, we don't know what it was like in its youth. By studying how galaxies like this one are growing and feeding their black holes and how the two are influencing each other, we could gain a better understanding of how galaxies were forming in the early universe."

The researchers have already noted one interesting finding: The tiny black hole seems to be consuming matter at around the same rate as its much more massive cousins. That could mean that supermassive black holes grow steadily throughout their lifetimes.

They hope that further research of the sort-of-primitive black hole will help them puzzle out how it and its cousins came to be.

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