One of the smallest galaxies ever discovered has a big surprise at its very center — a “supermassive” black hole of a gargantuan size that scientists thought could exist only in a galaxy 80 times bigger. In fact, the black hole at the center of galaxy M60-UCD1 is five times more massive than the black hole at the center of Earth’s own galaxy, The Milky Way, NASA scientists said Wednesday.
But The Milky Way is 500 times larger than the “dwarf galaxy,” discovered using the Hubble Space Telescope, NASA announced.
The tiny galaxy, pictured in the above NASA photo, sits in space about 54 million light years from Earth. One single light year is approximately 5.9 trillion miles, and is equivalent to the distance that light travels through a vacuum in a period of one Earth year.
The “dwarf galaxy” contains a mere 140 million stars, a tiny fraction of the 300 billion stars in the Milky Way galaxy. But M60-UCD1 is a diminutive 300 light years in diameter, meaning that its stars are packed much more densely than in the Milky Way galaxy.
According to the NASA scientists, a person who looks up from Earth on a clear night is able to see about 4,000 stars in the sky. But a hypothetical individual living on a planet inside M60-UCD1 would look up at night and see a sky crammed with one million visible stars.
But as amazing as discovery of the miniature galaxy may be, scientists are far more thrilled by the discovery of what they call a “monster” black hole at the galaxy’s core. Until today, physicists believed that small galaxies contained small black holes, while larger galaxies housed larger ones. But the discovery announced Wednesday flies in the face of accepted scientific wisdom.
“This gives us a whole new home for black holes that we never knew existed before,” said astronomer Amy Reines of the University of Michigan, who participated in the study that discovered the massive black hole.
Reines also said that the discovery of such an enormous black hole in a tiny galaxy proves that such “dwarf galaxies,” rather that just being free-floating groups of stars, must be the broken-off pieces of much larger galaxies that separated billions of years ago.
“There are quite a few of these ultra-compact dwarf galaxies and people have debated the nature of these objects for a long time,” she explained. “Are they just really, really massive star clusters — because that’s really what they look like — or are they the stripped nuclei of galaxies? This one is the first clear case that it is a stripped galaxy nucleus.”
The researchers figured out that the super massive black hole makes up an incredible 15 percent of the micro-galaxy’s mass. Even a typical “monster” black hole takes up only one half of 1 percent of a galaxy’s mass.