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Around 800 million light years from Earth, two large black holes are circling each other at a distance closer than any other pair humans have ever detected. One day, millions of years from now, they will merge in a crash that will rattle the fabric of reality itself.
In a paper published in The Astrophysical Journal, a team led by Anna Trindade Falcão, a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics, wrote that limits on telescope resolution, and other technical limitations, make studying these kinds of dual black hole systems inherently difficult. Yet examining them offers a unique way of learning about the formation of supermassive black holes, which exist at the center of almost all known galaxies.
The team was looking at images taken by the Hubble Space Telescope of a galaxy known as MCG-03-34-64, which is about 800 million light years away from Earth. They spotted three glowing blobs, which indicated the presence of huge amounts of glowing oxygen gas compressed into a small area. In visible optical wavelengths, the two black holes appear so close together that they merge into a single entity. In a statement, NASA compared the pair to “two Sumo wrestlers squaring off.”
Using the NASA’s Chandra observatory X-ray telescope, the astronomers saw two separate but powerful sources of emissions within the blobs. Since black holes also emit a lot of radio waves, they consulted archival data from the area and found, once again, powerful discharges. “We put these pieces together and concluded that we were likely looking at two closely spaced supermassive black holes,” said Trindade Falcão.
The source of the third blob of oxygen spotted by Hubble is not yet known. These types of black holes are also known as active galactic nuclei, as they are found at the center of galaxies. The pair likely began circling each other after their galaxies collided in the distant past. Eventually, in another 100 million years or so, the two black holes will merge, sending out gravitational shockwaves that will distort space-time over vast stretches of space.
The discovery of the two black holes was “serendipitous,” the astrophysicists wrote. Trindade Falcão said it was made possible by Hubble’s “amazing resolution.”
“We were not expecting to see something like this,”she added. “This view is not a common occurrence in the nearby universe, and told us there’s something else going on inside the galaxy.”
In the study, Trindade Falcão and her colleagues didn’t rule out other explanations for what was happening, including that this was actually just a single supermassive blackhole with some odd readings, but said the evidence for their conclusion was far stronger.
While similar black hole pairs have been previously observed, including a duo that’s a mere 89 million light years away from Earth, the newly discovered binary is notable for their proximity. At 300 million light years apart, it’s the closest confirmed pair of black holes in the local universe (an area of space spanning around 1 billion light years in radius that includes the Milky Way and numerous other galaxies). According to NASA, radio signals have shown hints of another binary black hole pair that may be closer together, but that has yet to be confirmed with X-ray and visible light evidence.
