Scientists are astonished by their discovery of a supermassive black hole in a “relative desert,” a location unlike the usual dense galaxy clusters they are found in. Part of the realization is that there may be bigger populations of these monstrous black holes than commonly thought.
The newly detected supermassive black hole contains 17 billion solar masses. It sits smack in the center of Galaxy NGC 1600, situated 200 million light years away from Earth and was an unlikely home for this gigantic black hole since it belongs to an average-sized galaxy group.
The stars surrounding NGC 1600 also behave as if the black hole were a binary black hole, something expected to more commonly occur in large galaxies and not its unusual location.
After stumbling on these monster black holes in unlikely places, the researchers – discussing their findings in the journal Nature – speculated that the population of black holes in the universe may then be much bigger than thought.
Black holes form with matter becoming so dense that not even light can escape the pull of gravity. In the early days of the universe, gas was so abundant that many black holes grew to an extremely massive size by swallowing it up, giving off intense amounts of energy.
These supermassive black holes appear as ultra-bright quasars when one looks back in time at the far universe, but as one looks closer to Earth, the view is of galaxies with little gas (already turning into stars) and no quasars. The most gigantic of the local galaxies, however, shelter old quasars at the core.
NGC 1600, an old galaxy with little new star formation, is in a lesser populated part of the universe. Since barely inhabited regions like these are far more common than the superdense ones where the largest black holes are typically found, then finding a supermassive black hole in it may just be “the tip of an iceberg,” according to lead scientist Chung-Pei Ma.
Seeking an answer for just how common these huge bodies are is the Massive Survey, a multi-telescope venture founded in 2014 for weighing the stars, dark matter, as well as central black holes of the 100 largest nearby galaxies – particularly bigger than 300 billion solar masses and within 350 million light-years of our planet. One of its early triumphs is NGC 1600’s supermassive black hole.
"I'm confident we're going to find black holes – if we don't, that would be really, really strange,” says Ma.
The question, she points out, is how massive the black holes could get. Will they, for instance, stop growing at 20 billion solar masses or assert themselves as even bigger monsters?
The largest known black hole weighs 21 billion suns and is found in the Coma galaxy cluster, where there are over a thousand galaxies. These rich galaxy clusters are very rare, but with observations of NASA’s Hubble Space Telescope and the Gemini Telescope in Hawaii of a gigantic black hole in a sparsely populated galaxy region, there are potentially more outside of the Coma cluster types.
“What this is saying is that you don’t need these galaxy clusters to grow very massive black holes,” says University of Southampton's Professor Poshak Gandhi, who was not involved in the study.
Now, University of California Berkeley researchers continue to scour the Earth’s vicinity for more of these black hole wonders.
