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Massive black hole in tiny galaxy, astronomers say

By Keith McCord | Posted - Sep. 18, 2014 at 8:49 p.m.


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SALT LAKE CITY — A University of Utah astronomer and his colleagues made an amazing discovery that could change how scientists study the universe.

Anil Seth, an assistant professor of physics and astronomy at the University of Utah, and about a dozen other astronomers around the world used data and images from the Hubble Space and the Gemini telescope in Hawaii and discovered that the smallest known galaxy has a huge black hole — something scientists never really considered before.

“We knew pretty much right away that we had an interesting discovery on our hands,” Seth said.

The ultracompact dwarf galaxy named M60-UCD1 is the smallest known to contain a supermassive black hole with a mass equal to 21 million suns.

“We believe this once was a very big galaxy with maybe 10 billion stars in it, but then it passed very close to the center of an even larger galaxy, M60, and in that process all the stars and dark matter in the outer part of the galaxy got torn away and became part of M60,” he said.

“That was maybe as much as 10 billion years ago. We don’t know.”

M60-UCD1 is roughly 54 million light years from Earth, or about 320 billion miles.

The find means there are likely more black holes out there, and there are new places to look for them.

“We actually don't know how super massive black holes form in the centers of galaxies. There are theories for it, but we don't actually have a good understanding of how that happens,” Seth said. “One of the ways we can figure it out is to actually count up all the black holes that are out there in galaxies, and this opens up a new place to look for those black holes.”

Black holes aren't holes at all. They are huge areas packed with massive amounts of matter, tremendous gravity, and so dense that even light won't go through them. Black holes are found in the center of giant galaxies, like our own Milky Way. New galaxies have lots of stars.


We can see 10,000 stars in our night sky if you're in a really dark place, here on Earth. And on this galaxy there would be millions (of stars), and the night sky would be as bright as the daytime sky for sure, maybe brighter.

–Anil Seth


“We can see 10,000 stars in our night sky if you're in a really dark place, here on Earth,” Seth said. “And on this galaxy there would be millions (of stars), and the night sky would be as bright as the daytime sky for sure, maybe brighter.”

This tiny galaxy is a few hundred light years across, while the Milky Way is tens of thousands of light years across. A light year is the distance light can travel in one year. One light year is about 6 trillion miles.

That could change how we study the universe.

"It's some place that people didn't think about looking before, and now we are going to do that,” Seth said.

Seth was lead author of an international study of the dwarf galaxy published in Thursday’s issue of the journal Nature. The study — conducted by Seth and 13 other astronomers — was funded by the National Science Foundation in the U.S., the German Research Foundation, and the Gemini Observatory partnership, which includes the National Science Foundation, and scientific agencies in Canada, Chile, Australia, Brazil and Argentina.

Seth will deliver a public lecture about tiny galaxies and big black holes Saturday, Sept. 20 at 7 p.m. at the Clark Planetarium’s ATK IMAX Theater in downtown Salt Lake City. Tickets are $2 for the general public on first-come basis.

“It seems like it’s a topic that people really get excited about,” Seth said, “so it’s fun to be doing work on it and exciting to be able to share it with everybody.”

Contributing: Viviane Vo-Duc

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Keith McCord

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