Astronomers have detected a cosmic collision waiting to happen in a giant object just 3 billion years after the Big Bang.
The galaxy called J0749 + 2255 actually consists of two galaxies merged into one, and it does not have a supermassive black hole, but two. It just so happens that these two black holes are on a collision course, separated by a relatively small distance of only 10,000 light-years.
This isn’t the first time we’ve witnessed a near black hole collision, but J0749+2255 is a rare gem. Spotted early in the universe, both black holes are very active quasars.
It’s a discovery that could help scientists work to solve the ongoing and perplexing mystery of how supermassive black holes grow to such gigantic sizes.
“We don’t see a lot of double quasars this early in the universe. That’s why this discovery is so exciting,” she said. He says Astronomer Yu Qing Chen of the University of Illinois at Urbana-Champaign.
Quasars are among the brightest objects in the universe. It contains an active galactic nucleus – the center of a galaxy that hosts a supermassive black hole that is gulping down massive amounts of material.
Black holes don’t emit any light of their own that we can currently detect. The massive amount of material orbiting the black hole is heated by intense friction and gravity so that it not only glows, but smolders across the vast, dark gulfs of space-time.
Many of the early universe’s galaxies are quasar galaxies, and some in the near universe have two or even three quasars at their centre. This happens when galaxies collide and merge, each with its own supermassive black hole. The two black holes fall toward each other, and eventually—we think—merge to form a supermassive black hole.
But it’s a little more difficult to spot these mergers in the early universe. The light from J0749+2255 has traveled over 10 billion years to reach us; What we see in the galaxy is very small and faint compared to the objects much closer to us. At that distance, the distance between supermassive black holes bound together by gravity is too small for our current instruments to see.
The faint difference in light from J0749+2255 detected by the Gaia telescope suggests that there may be something more going on with the galaxy than was immediately apparent…but there are several possible causes, among them the double quasar. The team had to dig deeper to find out what was really going on.
“The confirmation process wasn’t easy, and we needed an array of telescopes spanning the spectrum from X-rays to radio to finally confirm that this system was indeed a pair of quasars, rather than two images, say, of a quasar’s gravitational lens.” He says Astronomer Yu Xin of the University of Illinois.
and J0749+2255 Special. Since both black holes are quasars, they are luminous enough to be able to distinguish. And they’re not close enough, yet, to be a gravitationally bound binary, which means they have enough separation for individual decision.
Using observations from a full array of ground-based and space telescopes, Chen and his colleagues analyzed the light from J0749+2255. They determined that the two black holes will likely evolve into a gravitationally bound tight binary in about 220 million years or so. The decaying orbit of this binary will eventually lead to a collision and merger into an even more massive black hole.
(They may have collided now, but this event is meaningless to us at present; that is why astronomers make such predictions in the present tense.)
The researchers also found that the two black holes are a relativistic intersection, registering at about 1.26 billion solar masses and 1.58 billion solar masses, respectively. These discoveries could begin to tell us something about the rate of supermassive black holes in the early universe – which will help astronomers understand the evolution of modern black holes that can be billions of solar masses in size.
There is still a lot to uncover, but J0749+2255 represents an important step forward.
“We are beginning to reveal this part of the iceberg for early binary groups of quasars,” says astronomer Shen Liu from the University of Illinois at Urbana-Champaign.
“That’s the uniqueness of this study. It actually tells us that this group exists, and now we have a way to identify paired quasars that are separated by a volume less than the size of a single galaxy.”
Research published in nature.
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