The Fastest-Growing Black Hole Ever Seen In The Universe
A supermassive black hole that grows so fast that it shines 7,000 times brighter than the entire Milky Way has just been found, hidden in plain sight. Every second, an amount of material equivalent to the mass of the Earth falls into this insatiable black hole.
As far as we know, it is the fastest growing black hole in the last 9 billion years: its activity is so frenetic that it sends light of multiple wavelengths through the Universe, making it what is known as a quasar. The black hole is called SMSS J114447.77-430859.3 (J1144 for short) and an analysis of its properties suggests that light from its feed has traveled about 7 billion years to reach us, clocking in at about 2.6 a billion times the mass of the Sun (a pretty respectable size for a supermassive black hole).
And there he was, hanging out, going unnoticed until now. But because of where it lies, 18 degrees above the galactic plane, previous surveys for quasars have managed to miss it, only skimming as close as 20 degrees above the Milky Way’s disk.
“A bit of historical bad luck has become our good luck,” astronomer Christopher Onken of the Australian National University told ScienceAlert.
“Searching for distant objects becomes very difficult when you look closely at the disk of the Milky Way: there are so many foreground stars that it is very difficult to find the rare background sources.
“Another team used an ultraviolet satellite to search for these luminous objects across the sky, but J1144 fell into a small gap in its coverage. But the source is bright enough to show up in pictures taken of the sky as far back as 1901, so it’s definitely a case of hiding in plain sight.”
Aside from supernova explosions that emit gamma-ray bursts, quasars are the brightest individual objects in the Universe. They are the result of a supermassive black hole accumulating matter at a tremendous rate, from a huge disk of dust and gas that spirals into the black hole like water down a drain. It is not the black hole itself that shines, but that material, heated by extreme friction and gravity, that produces light across the spectrum.
Additionally, astronomers believe that some of the material may be channeled and accelerated along magnetic field lines around the outside of the black hole toward the poles, where it is launched into space as high-speed jets of plasma. The interaction of these jets with the gas of the surrounding galaxy produces radio waves.
But there is something really strange about J1144. Quasars with the same level of activity can be found, but much earlier in the history of the Universe, dating back about 13.8 billion years.
After about 9 billion years ago, this furious quasar activity seems to have calmed down a bit, making J1144 a fascinating oddball. The quasar is so bright that someone with a backyard telescope could go outside and look at it with their own eyes.
“This black hole is so unusual that while you should never say never, I don’t think we’ll ever find another one like it,” says ANU astronomer Christian Wolf.
“We are pretty sure this record will not be broken. Basically, we’ve run out of sky where objects like this could hide.”
But the discovery has sparked a new fervor to search for and compile a census of bright quasars. The team has already confirmed 80 new quasars, with hundreds more candidates to be analyzed and confirmed or ruled out. This means that the astronomical community is close to a complete census of bright quasars in the relatively recent Universe.
“None of them are as bright as J1144, but they will help paint a more complete picture of how common this rapid growth phase could be, and that will help us understand the physical mechanism behind it,” Onken told ScienceAlert.
“Whether it’s about rare collisions between huge galaxies, or something special about the environment around the black hole, or about the black hole itself, for example, a rapidly spinning black hole can release much more energy from the matter it accumulates than one that barely turns.”
Also, because they’re so bright, the light from quasars can be analyzed to learn more about the tenuous gas drifting between galaxies, Onken said. This can reveal the flow of gas around the Milky Way galaxy, giving us a better understanding of three-dimensional motions in the space around us.
The team’s research has been submitted to Publications of the Astronomical Society of Australia and is available on the arXiv preprint server.