Three supermassive black holes have been discovered at the core of a distant galaxy, residing 4.2 billion light years from Earth, roughly one-third of the way across the observable Universe. Investigation of the odd galaxy was carried out using a network of radio telescopes separated by as much as 6,200 miles. This Very Long Baseline Interferometry (VLBI) technique provides 50 times more detail than the Hubble Space Telescope. Two of the black holes orbit close to one another.
The discovery suggests that these closely packed supermassive black holes are far more common than previously thought and has been published in the highly esteemed scientific journal Nature.
The team led by South African Dr Roger Deane from the University of Cape Town used a technique called Very Long Baseline Interferometry (VLBI) to discover the inner two black holes of the triple system. This technique combines the signals from large radio antennas separated by up to 10,000 kilometers to see detail 50 times finer than that possible with the Hubble Space Telescope.
Deane and his group originally became interested in this particular galaxy known by the unwieldy name SDSS J150243.091111557.3, because it had been flagged by the Sloan Digital Sky Survey (thus the “SDSS” in the name) as having what looked like two sources of bright light in its core.
That indicated the possibility of two black holes there with the light coming not from the invisible objects themselves but from the whirlpools of gas heated to incandescence as they spiral in under the black holes’ intense gravity. Jets emitted by the black holes pinpointed their location.
Astronomers have learned over the past decade or two that virtually every full size galaxy such as our own Milky Way has a giant black hole lurking in its core. These monsters weigh in with a mass equal to millions or even billions of stars. The new observations, however, described in the journal Nature, suggest that many galaxies have not one but two or more giant black holes in their centers, orbiting each other in a tight gravitational dance that will ultimately lead the objects to merge together into something even more gigantic. Watching these mergers will offer insight into how gravity behaves when stretched to its limits, astronomers predict, with clues revealed by monster black hole mash-ups such as the just-discovered triplet.
The two are close enough together that orbital interactions have twisted the jets of one black hole into an S-shaped curve. The authors estimate that the separation between the two is only 140 parsecs, making them the second-closest pair of supermassive black holes we’ve ever spotted. This is also only the fourth triple black hole system that’s been detected.
The authors think that the S-shaped jets might be a diagnostic indication of these closely spaced black hole systems. They looked at a total of only six galaxies before spotting this pair which they take as an indication that similar systems may be common, a contrast to previous searches which had found very few.
“This discovery not only suggests that close-pair black hole systems emitting at radio wavelengths are much more common than previously expected but also predicts that radio telescopes such as MeerKAT and the African VLBI Network will directly assist in the detection and understanding of the gravitational wave signal,” Jarvis posited. “Further in the future the Square Kilometer Array will allow us to find and study these systems in exquisite detail and really allow us to gain a much better understanding of how black holes shape galaxies over the history of the Universe.”
The researchers conclude by arguing that it’s worth continuing the search for more systems with multiple black holes. Identifying them will help us determine how common gravity waves of different frequencies are, which will help us design the next generation of detectors.
If this discovery is confirmed future astronomers could recognize the presence of closely orbiting black holes by the wavy jets stemming from the galactic center.
The galaxy SDSS J150243.09+111557.3 has now been found to possess a three-body black hole in its galactic core. Systems like these, possessing multiple black holes at the center of a galaxy, will eventually collapse into a single body, researchers theorize.
Discovery of the three-body family of black holes at the heart of SDSS J150243.09+111557.3 was profiled in the journal Nature.