Failed Supernova Forms Black Hole Without Explosion

In a paper available online and submitted to the Monthly Notices of The Royal Astronomical Society, a US team has looked at N6946-BH1, a red supergiant star that fits the bill for the failed supernova classification, a phenomenon never observed before.

“If confirmed, N6946-BH1 would be the first failed supernova and first black hole birth ever discovered and would resolve the problem of the missing high-mass supernova progenitors,” the researchers said in the paper.

The object, which is about 25 times the mass of the Sun, became about one million times more luminous in 2009, suggesting that the star might be getting ready to explode. Then the star disappeared from view, becoming six times fainter than it used to be before the outburst in a matter of months.

The researchers believe that the star was so massive that it didn’t have time to go supernova. In a supernova the core collapses on itself, releasing a lot of energy in the process. This rips the outer layers of the star apart and forms a very compact object, either a neutron star or a black hole. But it seems that in the case of N6946-BH1, the black hole formed before the star could explode.

Other ideas have been put forward to explain the curious object. Astronomers might be observing a new type of variable star, changing its luminosity in a matter of months. Another possibility put forward was a stellar merger. Both suggestions can explain some features, but the failed supernova is the only one that fits the full bill.

To confirm that this is indeed the case, the team is suggesting new observations of the object with current and upcoming observatories, like the James Webb Space Telescope, that could work out if there’s an actual black hole where a star should be.