Black Hole Or Supernova Star Explosion? Scientists Spot Galaxy’s Mysterious Bright Spot

Scientists may have found a new supernova explosion or supermassive black hole in a galaxy about 600 million light years from Earth after pointing a telescope there for the first time in a couple of decades and spotting something super bright near its center.

The National Radio Astronomy Observatory said the bright object was not in the Cygnus A galaxy when the Very Large Array last viewed it in 1996.

“It must have turned on sometime between 1996 and now,” the observatory’s Rick Perley said in a statement. They know it’s a new bright spot because despite upgrades that have been made to the telescope since the mid-’90s, “this new feature is bright enough that we definitely would have seen it in the earlier images [even] if nothing had changed.”

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Based on what it looks like, the scientists said the bright spot is either a supernova explosion or an “outburst” from a secondary supermassive black hole orbiting the one that lies at the galaxy’s center. The supermassive black hole explanation is the more likely contender, because of just how bright the object is, but if it is a supernova — an explosion of a massive star — it’s a rare kind.

“While they want to watch the object’s future behavior to make sure, they pointed out that the object has remained too bright for too long to be consistent with any known type of supernova,” the observatory said. “It has many of the characteristics of a supermassive black hole that is rapidly feeding on surrounding material.”

Cygnus A is known for being one of the greatest sources of radio waves in space, and the closest one to Earth that is so active on that side of the electromagnetic spectrum.

But much of its history is a mystery. Where would this secondary supermassive black hole have come from and why is it orbiting so close to the main one in Cygnus A? It’s possible that Cygnus A ate up another galaxy, lassoing its black hole into the system.

This kind of cannibalism is fairly common in the universe. Astronomers have recently found a few supermassive black holes lurking at the center of tiny galaxies called ultracompact dwarf galaxies. They believe such massive objects exist in such small systems because those dwarf galaxies were once much larger, but collided with other galaxies and had their contents stripped away. The victor of those galactic collisions ran away with the extra stars and planets and left behind a loser of a supermassive black hole with a smaller community of matter around it. There are also mergers of galaxies that result from these commonly occurring collisions.

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“These two would be one of the closest pairs of supermassive black holes ever discovered, likely themselves to merge in the future,” the NRAO’s chief scientist Chris Carilli explained.

If the bright spot is indeed a supermassive black hole that was roped into the galaxy from another, it could tell astronomers more about what Cygnus A’s life was like before telescopes and before it was discovered.

In the time since scientists first found Cygnus A, the black hole would have been there all along, if that’s what the object turns out to be. But the telescope would have been able to spot it now because, the observatory explained, the black hole might have “encountered a new source of material to devour,” such as gas or a star that got too close and was shredded into a stream of atoms and dragged into the void.

When a supermassive black hole at the center of a galaxy gobbles up a space meal, it can emit material in a sort of burp known as galactic outflow, a powerful wind of gas. Scientists have recently discovered that baby stars can be formed in that hot gas the black hole passes.