The European Southern Authority’s Very Large Telescope has just discovered the first dormant black hole.
Dormant stellar-mass black holes form when massive stars come to the end of their lives. They are difficult to spot because unlike regular black holes they do not emit high levels of X-ray radiation. Although they are thought to be fairly common, they haven’t been observed because they are difficult to detect.
The new black hole is named VFTS 243 and is at least nine times the mass of our sun. It orbits a hot blue star weighing 25 times our sun and makes it a binary system.
Found through a process of elimination. Astronomers first looked at 1,000 massive stars in the Tarantula Nebula region of the Large Magellanic Cloud, a galaxy near our own Milky Way.
They first identified black holes which were part of binary systems, stars that move around another cosmic body. Then they looked where the companion was not visible.
The main part of the analysis is elimination. “What can weigh nine solar masses and not emit any light? A black hole is the only possibility we have got left,” Tomer Shenar, coauthor of the study, said.
Some of the authors are known as the “Black hole police,” because they have debunked other ‘discoveries’ of believed black holes. The paper notes that 10 discoveries of black holes in binary systems are disputed, but are confident that VFTS 243 is not a false alarm.
But the group of scientists invited scrutiny. “In science, you’re always right until someone proves you wrong, and I cannot know that this would never happen — I only know that none of us can spot a flaw in the analysis,” Shenar said.
Tomer Shenar, who was working at KU Leuven in Belgium when the study began and is now a Marie-Curie Fellow at Amsterdam University, in the Netherlands.