According to a study published in Nature, a repeating light signal observed at a distance in the galaxy may be coming from the final stages of a merging of two supermassive black holes. Experts said this could be just a few hundredths of a light-year apart, which could be merging in a mere one million years.
A light signal coming from quasar PG 1302-102 was observed by Caltech’s Matthew Graham and his team while studying variability in quasar brightness using data from the Catalina Real-Time Transient Survey. The team has been monitoring 500 million celestial light sources across 80 percent of the sky with three ground telescopes.
Artist representation of supermassive black holes colliding (c) Andy Bohn
Among the observed 20 quasars that emit periodic optical signals, one is PG 1302-102’s clean, strong signal, which repeated every five years or so, stood out.
"It has a really nice smooth up-and-down signal, similar to a sine wave, and that just hasn't been seen before in a quasar," Graham explains in a statement.
Supermassive black holes exist at the center of most large galaxies. Experts say, it co-evolves with their host galaxies, which grow as galaxies merge. Black holes cannot be seen, thus researchers look for their surrounding bands of material called accretion disks, produced by the intense pull of the black hole’s gravity. The disks of supermassive black holes can release vast amounts of heat, X-rays, and gamma rays, which are the most luminous objects in the universe.
How black holes form. Wait, are these puppies?
About the quasar that stood out, co-author Eilat Glikman of Middlebury College said, "But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data."
Experts say, the reason behind could be a supermassive black hole binary. "That suggests something else, such as a second black hole, is perturbing this system," Glikman added.
"The end stages of the merger of these supermassive black hole systems are very poorly understood," Graham says. "The discovery of a system that seems to be at this late stage of its evolution means we now have an observational handle on what is going on."
Study co-author Daniel Stern of JPL added, "The black holes in PG 1302-102 are, at most, a few hundredths of a light-year apart and could merge in about a million years or less.” And when that happens, The New York Times reports, it’ll release as much energy as 100 million supernova explosions.