The black hole was detected by a gravitational lensing technique (Getty)
According to researchers, a black hole has been detected that could be four times the size of our “freely floating” sun across our galaxy.
Researchers at the University of California say there could be up to 200 million “freely floating” black holes in our Milky Way galaxy.
Black holes are invisible unless they are part of a stellar track or are surrounded by an accretion disk.
The researchers used “gravitational microlens”, where the black hole distorts and illuminates the light coming from “behind” as seen from Earth.
Researchers are still unsure whether the object is a black hole or a neutron star (the heavy “core” that remains after a supernova explosion.
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The team, led by graduate student Casey Lam and Jessica Lu, an associate professor of astronomy at UC Berkeley, estimates that the mass of the invisible compact object is 1.6 to 4.4 times that of the sun. .
Because astronomers think the remains of a dead star must be heavier than 2.2 solar masses to collapse into a black hole, UC Berkeley researchers warn that the object could be a star of neutrons instead of a black hole.
Neutron stars are also dense and very compact objects, but their gravity is balanced by the internal pressure of neutrons, which prevents a subsequent collapse of a black hole.
Whether it’s a black hole or a neutron star, the object is the first dark stellar remnant, a stellar “ghost”, discovered wandering the galaxy unmatched by another star.
Determining how many of these compact objects populate the Milky Way will help astronomers understand the evolution of stars — particularly how they die — and our galaxy.
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It could also reveal if any of the invisible black holes are primordial black holes, which some cosmologists believe occurred in large numbers during the Big Bang.
The story goes on
The analysis of Lam, Lu and his international team has been accepted for publication in The Astrophysical Journal Letters.
The team also concluded that the probable population of black holes in the galaxy is 200 million, roughly what most theorists predicted.
Lam said the length of the lens event was the main information the investigators were looking at a black hole. In 2020, he showed that the best way to look for black hole microlenses was to look for very long events.
It is likely that only 1% of detectable microlens events come from black holes, he said, so looking at all events would be like looking for a needle in a haystack.
But, Lam calculated, about 40 percent of microlens events lasting more than 120 days are likely to be black holes.
“The duration of the brightness event is an indication of the large amount of the foreground lens that doubles the background star’s light,” Lam said.
“Long events are more likely because of black holes. It’s not a guarantee, though, because the duration of the glare episode depends not only on the massive mass of the foreground lens, but also on how quickly the foreground lens and the background star move relatively close to each other.
“However, by also obtaining measurements of the apparent position of the background star, we can confirm whether the foreground lens is really a black hole.”
I will see; The image shows a black hole inside the Milky Way