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The mess created by an encounter between a black hole and an unlucky star has delivered a rare and incredible treasure.
By measuring X-ray radiation as the star was torn apart by gravity, astronomers determined that the black hole is an incredibly elusive beast: an intermediate-mass-to-medium-weight black hole, located between the stellar-mass lightweights and the stars. supermassive heavyweights.
Scientists believe intermediate mass black holes (IMBHs) could be incredibly common, but for some reason they have been shown to be able to escape detection. help us unravel the mystery of how supermassive black holes reach their enormous size.
“The fact that we were able to catch this black hole as it devoured a star provides a remarkable opportunity to observe what would otherwise be invisible,” said astronomer Ann Zabludoff of the University of Arizona.
“Not only that, by analyzing the eruption, we were able to better understand this elusive category of black holes, which may well represent the majority of black holes in the center of galaxies.”
While the boundaries between IMBHs and supermassive black holes (SMBHs) are currently not very well defined, intermediate mass black holes are generally considered to be larger than a collapsed star or a typical stellar black hole (up to a hundred solar masses) but not supermassive. (between a million and a billion times more mass than a typical stellar black hole).
The dearth of detections in the IMBH mass range to date is glaring. So far, astronomers have managed to come up with a handful of observations that suggest IMBHs, but modeling suggests there should be many more.
Black holes, which are usually invisible, reveal themselves when something like a star gets too close. Then the black hole’s immense tidal force – the product of its gravitational field – first stretches and then pulls the star so hard it tears apart.
This Tidal Disturbance Event (TDE) releases a brilliant flare of light before debris from the disintegrated star gradually disappears beyond the black hole’s event horizon.
One such event, named 3XMM J215022.4−055108 (J2150 for short), was observed in 2003 at the center of a star cluster on the outskirts of a galaxy 740 million light years away. Over the past 10 years, the glow of light has faded, providing a wealth of data about the event. Photon analysis suggested an IMBH.
Led by University of Arizona astronomer Sixiang Wen, the new team reanalyzed the data, comparing it to sophisticated theoretical models, to more accurately measure the black hole’s mass and spin. They discovered that the culprit reached around 10,000 solar masses.
And, fascinatingly, it turns very quickly. The researchers were able to use this rapid rotation to probe the nature of dark matter. We don’t know what dark matter is, but we do know that if it were made up of hypothetical particles called ultralight bosons, the black hole wouldn’t be able to spin as fast as it has been observed.
The black hole’s rapid rotation also offers some clues as to how it developed.
“It’s possible that the black hole formed this way and hasn’t changed much since, or that two intermediate-mass black holes recently merged to form this one,” Zabludoff said.
“We know that the rotation we measured excludes scenarios in which the black hole grows over a long period of time due to constant gas consumption or many quick snacks on gas arriving from random directions.”
We know that mergers can produce black holes in the intermediate mass range; one of them was detected in 2019, producing a black hole 142 times the mass of the Sun. What we don’t know is how often this happens and if that’s the only way black holes can grow to this size. We’ll have to locate more to figure it out.
One place we might find them is at the center of dwarf galaxies. We know that the centers of almost all galaxies of the Milky Way mass or larger host supermassive black holes, and that the mass of the black hole is proportional to the mass of the spherical distribution of stars concentrated in the middle of the galaxy. , known as its bulge.
It stands to reason that small galaxies should therefore have smaller black holes, but observing them has proven difficult. But, if most dwarf galaxies are orbiting an IMBH, then we might be able to detect them from their tidal disturbance eruptions. First, we will have to increase the detection rate, but future instruments should improve it considerably.
“By adapting the X-ray emission from these flares to theoretical models, we can perform a population census of intermediate mass black holes in the universe,” Wen said.
The research was published in The Journal of Astrophysics.
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