Astronomers discover ‘needle in a haystack’: A ‘quiet’ black hole created without a blast
Large Magellanic Cloud, this newly-discovered black hole was formed as others were, with the collapse of a star.
But it is different because it is “X-ray quiet,” in that it was found without the telltale signs of X-ray radiation, researchers led by astrophysicist Tomer Shenar at the University of Amsterdam in the Netherlands reported this week in the journal Nature Astronomy. Astronomers typically find black holes by identifying radiation given off from matter being sucked into the black hole.
“We identified a ‘needle in a haystack’,” Shenar said in a discussion of the findings on the Harvard-Smithsonian Center for Astrophysics website.
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‘No sign of a previous explosion’
Also different about this black hole, which weighs nine times the mass of our sun and orbits a hot, blue star with 25 times the sun’s mass: The star that collapsed to create the black hole vanished without the typical explosion or “kick” upon its collapse, researchers said.
“The star that formed the black hole … appears to have collapsed entirely, with no sign of a previous explosion,” Shenar said. “Evidence for this ‘direct-collapse’ scenario has been emerging recently, but our study arguably provides one of the most direct indications. This has enormous implications for the origin of black-hole mergers in the cosmos.”
Other possible candidates have been identified previously, but the researchers say this is the first “dormant” stellar-mass black hole to be unambiguously detected outside of the Milky Way galaxy.
Astronomers examined nearly 1,000 stars in analyzing six years of observations with the European Southern Observatory’s Very Large Telescope in Chile.
Kareem El-Badry, an astrophysicist in the Center for Astrophysics who earned the nickname “the black hole destroyer,” due to his proclivity for debunking black hole discoveries, said he was skeptical when asked to confirm the findings.
“I had my doubts. But I could not find a plausible explanation for the data that did not involve a black hole,” El-Badry said. “Of course I expect others in the field to pore over our analysis carefully, and to try to cook up alternative models. … It’s a very exciting project to be involved in.”
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