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Astronomers find the tiniest galaxy ever to contain a supermassive black hole, doubling our estimation of black holes in the universe

Editor's note: This video contains no audio. University of Utah astronomer Anil Seth led an international research team that discovered the smallest galaxy known to harbor a supermassive black hole. The video simulation shows how this small galaxy, named M60-UCD1, was formed from a larger, normal galaxy. Seth says that while this process took about 500 million years, astronomers don't know when it happened, and that it could have been billions of years ago. (Video: Holger Baumgardt, University of Queensland)

A supermassive black hole has been spotted in the tiniest galaxy yet --  an ultracompact dwarf galaxy -- which suggests that black holes could be in places we haven't even thought to look yet.

The galaxy, named M60-UCD1 and reported in a new Nature study, is 0.2 percent the size of the Milky Way, but contains a black hole with the mass of 21 million suns. That's 15 percent of the galaxy's total mass, which is pretty staggering compared to the less than .01 percent taken up by the Milky Way's personal black hole.

Astronomers believe that the galaxy, which is a ball of about 100 million stars, used to be much bigger -- with a more sensible star-to-black-hole ratio. But as M60-UCD1 orbited a much larger galaxy, the force of it stripped all of its outer parts away. The little dwarf with a big black hole was left behind, still orbiting its larger neighbor.

We already know that big galaxies, like our own, have black holes in their centers, and that there are probably millions of them out in the universe. But this discovery gives astronomers new targets to search in.

"This discovery could actually double the number of black holes in the universe," said Anil Seth, an assistant professor of physics and astronomy at the University of Utah and lead author of the study. "There are lots of ultra compact galaxies like this one, and it's possible that many of them have black holes as well."

It's going to take more than one dwarf to prove that, but any opportunity to study black holes is a good one. "They're part of the origin story of us, and our universe," Seth said. "Every galaxy like ours has one of these, and we know that they affect how galaxies evolve and how stars form." But we still don't understand why black holes end up where they do. "If you want to understand how we got here, figuring out the role that black holes play is an important part of that," Seth said.