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A group of astrophysicists backed by the European Union has found a dormant black hole in a nearby galaxy, whose mass is nine times the mass of our Sun.
An international research team has discovered a dormant stellar-mass black hole in a neighboring galaxy, dubbed the “Large Magellanic Cloud.” This is the first time that this type of black hole, formed by the gravitational collapse of a star, has been identified outside our galaxy.
The research was carried out with the support of the MULTIPLES, PROGENITOR and TEL-STARS projects, financed with European funds. The finding is described in the study published in the journal “Nature Astronomy.”
“We identified a ‘needle in a haystack'”, highlights Dr. Tomer Shenar, first author of the study, in a news item published in “SciTechDaily”. The astrophysicist began his research at the Catholic University of Leuven (Belgium), the host entity of the MULTIPLES project, and is now the beneficiary of a Marie Skłodowska-Curie individual research grant at the University of Amsterdam (the Netherlands), the coordinating entity of the project. PROGENITOR.
Recently, scientists have discovered that massive stars rarely exist alone, but instead occur in pairs, as part of a binary system. However, when such high-mass stars collapse under their own gravity at the end of their lives, they generate stellar-mass black holes. In a binary system, that creates an orbiting black hole with a bright companion star.
Since dormant black holes do not emit high levels of X-ray radiation, they are very difficult to detect. “It is incredible that we hardly have any evidence of inactive black holes, considering how common astronomers think they are,” Dr. Pablo Marchant, co-author of the Catholic University of Leuven, comments in the news.
Now, after six years of observations with the European Southern Observatory’s Very Large Telescope, the team has succeeded in identifying a binary system in our neighboring galaxy. The binary system, named “VFTS 243”, consists of an inactive black hole with a mass of at least 9 times that of the Sun, orbiting a bright blue star with a mass 25 times that of the Sun.
a missing star
The astrophysicists also found that the star from which the black hole arose had totally collapsed, leaving no trace of a massive explosion. “Evidence for this ‘direct collapse’ scenario has only recently emerged, but our study provides possibly one of the most direct indications,” says Shenar. “That has huge implications for where black hole mergers come from in the cosmos.”
In order to find the VFTS 243 system, the researchers studied nearly 1,000 massive stars within the Tarantula Nebula region of the Large Magellanic Cloud. “As a researcher who has dismissed possible black holes in recent years, I was very skeptical about this discovery,” says Shenar. And he was not the only one. Dr. Kareem El-Badry, co-author of the study from the Harvard-Smithsonian Center for Astrophysics in the United States, shared his skepticism. “When Tomer asked me to double check his findings, he was hesitant. However, I couldn’t find a plausible explanation for the data that didn’t involve the existence of a black hole,” explains El-Badry.