Supermassive Black Hole Found In Ultracompact Dwarf Galaxy For The First Time

Chuck Bednar for redOrbit.com – Your Universe Online
Using the Hubble Space Telescope and other instruments, astronomers from the University of Utah and an international team of colleagues have discovered a supermassive black hole in the ultracompact dwarf galaxy M60-UCD1, making it the smallest galaxy ever found to host one of these enormous light-sucking objects.
[ Watch the Video: Artist’s Impression Of Dwarf Galaxy M60-UCD1′s Formation ]
Anil Seth, an assistant professor of physics and astronomy at the university, and his colleagues report in the September 18 edition of the journal Nature that the galaxy is located approximately 50 million light-years away and roughly 1/500th the diameter of the Milky Way. In addition, it is home to about 140 million stars, making it the densest dwarf galaxy ever observed.
M60-UCD1 was also found to be home to a black hole with a mass of more than 20 million suns, and this discovery suggests that several other ultracompact dwarf galaxies (UCDs) also contain supermassive black holes, the study authors said. Furthermore, their research indicates these dwarf galaxies could be the remnants of larger galaxies that were torn apart during collisions with other galaxies.

Image Above: Hubble image of Messier 60 and M60-UCD1. Credit: NASA, ESA and A. Seth (University of Utah, USA)
[ Watch the Video: Zoom Into Galaxy Pair Arp 116 ]
“It is the smallest and lightest object that we know of that has a supermassive black hole. It’s also one of the most black hole-dominated galaxies known,” Seth explained in a statement. “There are a lot of similar ultracompact dwarf galaxies, and together they may contain as many supermassive black holes as there are at the centers of normal galaxies.”
Using images captured by Hubble and observations conducted with the Gemini North 8-meter optical-and-infrared telescope in Hawaii, the astronomers found that the black hole at the heart of the galaxy comprises 15 percent of its total mass, and weighs five times more than the one located at the center of the Milky Way.
“That is pretty amazing, given that the Milky Way is 500 times larger and more than 1000 times heavier than M60-UCD1,” explained Seth. “In fact, even though the black hole at the center of our Milky Way galaxy has the mass of 4 million Suns it is still less than 0.01 percent of the Milky Way’s total mass, which makes you realize how significant M60-UCD1’s black hole really is.”
[ Watch the Video: Pan Across Galaxy Pair Arp 116 ]
The Hubble images provided information about the diameter and stellar density of the galaxy, while Gemini’s observations helped the research team measure the movement of the stars as they are impacted by the gravitational pull of the black hole. They then combined the data to calculate the mass of the unseen black hole.
According to Irene Klotz of Discovery News, the findings could help resolve a long-standing mystery surrounding UCDs, as scientists have long suspected that they had previously been far larger, but had been stripped of their stars by neighboring galaxies, ultimately leaving behind just the dense center and supermassive black hole.
If they are correct about other UCDs having supermassive black holes at the center, Seth told the Washington Post that their conclusions “could actually double the number of black holes in the universe. There are lots of ultra compact galaxies like this one, and it’s possible that many of them have black holes as well.”
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