July 18 () –
A team of international experts known for debunking black hole discoveries has found an inactive stellar-mass black hole in the Large Magellanic Cloud, a neighboring galaxy of the Milky Way, as published in the journal ‘Nature Astronomy’.
“For the first time, our team came together to report the discovery of a black hole, instead of rejecting one“, explains the director of the study, Tomer Shenar, a Marie-Curie fellow at the University of Amsterdam (The Netherlands).
The team, including Kareem El-Badry, dubbed the ‘black hole destroyer’ by his astronomer colleagues, from the Center for Astrophysics/Harvard and Smithsonian (CfA), in the United States, discovered that the star that gave rise to the black hole vanished without any sign of a powerful explosion.
“We have identified a ‘needle in a haystack’ Shenar says. Although other similar black hole candidates have been proposed, the team claims that this is the first “dormant” stellar-mass black hole to be unambiguously detected outside the Milky Way.
Stellar-mass black holes form when massive stars reach the end of their lives and collapse under their own gravity. In a binary, a system of two stars revolving around each other, this process leaves an orbiting black hole with a bright companion star. The black hole is “dormant” if it is not emitting high levels of X-ray radiation, which is how these black holes are usually detected.
The discovery was made thanks to six years of observations obtained with the Very Large Telescope (VLT) of the European Southern Observatory (ESO).
“It’s amazing that we barely know of dormant black holes, considering how common astronomers think they are.admits co-author Pablo Marchant of the University of Leuven (KU Leuven) in Belgium. The newly discovered black hole is at least nine times the mass of the Sun and orbits a hot, blue star weighing 25 times the mass of the sun.
Dormant black holes are especially difficult to detect, since they don’t interact much with their surroundings. “We have been looking for this type of binary black hole system for more than two years explains co-author Julia Bodensteiner, an ESO researcher in Germany. I was very excited when I heard about VFTS 243, which in my opinion is the most compelling candidate reported to date.”
To find VFTS 243, the collaboration searched for nearly 1,000 massive stars in the Tarantula Nebula region of the Large Magellanic Cloud, looking for those that might have black hole companions. Identifying these companions as black holes is extremely difficult, as many alternative possibilities exist.
“As a researcher who has debunked possible black holes in recent years, I was extremely skeptical of this discovery.Shenar acknowledges.
“When Tomer asked me to check his conclusions, I had my doubts. But I couldn’t find a plausible explanation for the data that didn’t involve a black hole,” explains El-Badry.
The discovery also allows the team a unique insight into the processes that accompany the formation of black holes. Astronomers believe that a stellar-mass black hole forms when the core of a dying massive star collapses, but whether or not this is accompanied by a powerful supernova explosion remains uncertain.
“The star that formed the black hole in VFTS 243 appears to have completely collapsed, with no signs of a previous explosion. Shenar explains. Evidence for this ‘direct collapse’ scenario has recently emerged, but our study provides possibly one of the most direct indications. This has huge implications for the origin of black hole mergers in the cosmos.“, he highlights.
The black hole in VFTS 243 was discovered thanks to six years of observations of the Tarantula Nebula by the Fiber Large Array Multi Element Spectrograph (FLAMES) instrument on ESO’s VLT. FLAMES allows astronomers to observe more than a hundred objects at once, saving significant telescope time compared to studying each object one by one.
Despite the moniker ‘black hole police’, the team actively encourages scrutiny, and hope their work will lead to the discovery of other stellar-mass black holes orbiting massive stars, predicted to exist in the thousands in the Earth. Milky Way and in the Magellanic Clouds.
“Of course, I hope that other experts will take a good look at our analysis and try to come up with alternative models. El-Badry says. It’s a very exciting project to be involved in.”
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