Astronomers have discovered a near-record breaking supermassive black hole, weighing in at 17 billion suns. However, it has astronomers puzzled as it was found in the most unlikely of places.
NASA’s Hubble Space Telescope and the Gemini Telescope in Hawaii were the first to observe the supermassive black hole, with the unexpected behemoth lying deep inside the isolated galaxy NGC 1600, around 200 million light years from Earth in the direction of the constellation Eridanus.
The largest supermassive black holes — roughly 10 billion times the mass of our sun — have only been found at the cores of very large galaxies in expanses of the universe which are packed with other large galaxies. The largest to have ever been found weighs in at 21 billion suns, residing in the crowded Coma galaxy cluster consisting of over 1,000 galaxies.
This new find now indicates these colossal objects may be more common than once thought. Chung-Pei Ma from the University of California Berkeley, who led the international team of researchers, saying in a statement:
“The newly discovered supersized black hole resides in the center of a massive elliptical galaxy, NGC 1600, located in a cosmic backwater, a small grouping of 20 or so galaxies. There are quite a few galaxies the size of NGC 1600 that reside in average-size galaxy groups.
“We estimate that these smaller groups are about 50 times more abundant than spectacular galaxy clusters like the Coma cluster. So the question now is, ‘Is this the tip of an iceberg?’ Maybe there are more monster black holes out there that don’t live in a skyscraper in Manhattan, but in a tall building somewhere in the Midwestern plains.”
The researchers were also surprised to find the black hole was 10 times more massive than what was predicted for a galaxy of this mass. Using previous surveys of black holes by Hubble, astronomers had established a connection between a black hole’s mass and the mass of its host galaxy’s central bulge of stars (the larger the galaxy bulge, the proportionally more massive the black hole).
However, galaxy NGC 1600 massive black hole’s mass is far beyond the mass of its relatively sparse bulge, with Ma saying:
“It appears that that relation does not work very well with extremely massive black holes; they are a larger fraction of the host galaxy’s mass.”
One explanation of the black hole’s monster size would be that it had merged with another black hole long ago when the galaxy interactions would have been more frequent.
When two galaxies merge, their central black holes settle into the core of the new galaxy, and then orbit each other. Stars that are falling near the binary black hole can actually deprive the momentum of the whirling pair, and then can pick up enough speed to escape from the galaxy’s core — depending on their speed and trajectory.
It is this gravitational interaction that causes the black holes to slowly move closer together, helping them to eventually merge to form an even larger black hole. The then supermassive black hole will continue to grow by devouring the gas funneled to the core by galaxy collisions. Ma said that:
“To become this massive, the black hole would have had a very voracious phase during which it devoured lots of gas.”
The frequent meals consumed by NGC 1600 may also explain why the galaxy has few galactic neighbors. NGC 1600 is the most dominant galaxy in its galactic group, being at least three times brighter than that of its neighbors. Most of the galaxy’s gas was consumed a long time ago when the black hole was a brilliant quasar from material streaming into it that was heated into a glowing plasma. Ma explained:
“Other groups like this rarely have such a large luminosity gap between the brightest and the second brightest galaxies.
“Now, the black hole is a sleeping giant. The only way we found it was by measuring the velocities of stars near it, which are strongly influenced by the gravity of the black hole. The velocity measurements give us an estimate of the black hole’s mass.”