The dwarf galaxy M60-UCD1 has a supermassive black hole five times more massive than the Milky Way's. (Credit: NASA, ESA and A. Seth - University of Utah, USA)

An international team of astronomers have announced that theyve discovered a supermassive black hole at the center of the galaxy M60-UCD1. This is the smallest known galaxy to have a supermassive black hole.

It is the smallest and lightest object that we know of that has a supermassive black hole, lead researcher Anil Seth said in a press release. Its also one of the most black hole-dominated galaxies known.

M60-UCD1 is about 50 million light-years away from Earth and is much smaller than our own Milky Way. Its one of many ultra-compact dwarf galaxies that astronomers have discovered. Its diameter is only 300 light-years 1/500th of the diameter of our galaxy. And those 300 light years are packed with 140 million stars.

Despite their compactness, these types of galaxies still tend to be more massive than astronomers would otherwise expect. This has led some astronomers to theorize that as small as they are, these galaxies may contain supermassive black holes at their center.

We had already published a study that suggested this additional weight could come from the presence of supermassive black holes, but it was only a theory, co-researcher Steffen Mieske of the European Southern Observatory said in a statement. Now, by studying the movement of the stars within M60-UCD1, we have detected the effects of such a black hole at its center.

The astronomers detected the black hole by studying images of the galaxy that had been made with the Hubble Space Telescope and the Gemini North telescope in Hawaii. These images were then studied to determine the effect of the unseen black hole and determine information about it.

Through this data, the scientists determined that the black hole has the mass of about 21 million Suns five times more massive than the black hole at the center of the Milky Way. This black hole is so massive, in fact, that it comprises about 15 percent of the total mass of M60-UCD1. By comparison, the black hole at the center of the Milky Way comprises less than about 0.01% of the galaxys total mass.

If this type of black hole is discovered at the center of other ultra-compact galaxies, it could provide a good theory for how these galaxies form in the first place.

This finding suggests that dwarf galaxies may actually be the stripped remnants of larger galaxies that were torn apart during collisions with other galaxies, rather than small islands of stars born in isolation, Seth added in a release. We dont know of any other way you could make a black hole so big in an object this small.

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Astronomers Find A Supermassive Black Hole In A Tiny Galaxy