An explosion — about 100 times brighter than previously recorded — blinded scientists’ instruments.
Scientists marveled at the power of the gamma-ray beam, which probably marked the birth of a black hole.
The explosion may have been so bright because it was powered by a unique jet structure.
The brightest gamma-ray explosion ever recorded, so bright it blinded scientific instruments, only got weirder.
GRB 221009, first spotted in October 2022, outpaced other cosmic explosions on record by “not just a little bit, but a hundred times,” George Washington University graduate Brendan O’Connor said in a press release.
The explosion earned it the nickname BOAT for “Brightest of All Time.”
Astronomers have since tried to figure out what could have made the gamma-ray burst so bright, and may finally have an answer.
Researchers have found that the gamma-ray explosion ejected a jet with an unusual structure that swept away a large amount of stellar material. The discovery, they say, could shed new light on the origin of the universe.
Gamma-ray bursts shed light on the origin of stars
Gamma-ray bursts (GRBs) are enormously powerful explosions, releasing more energy into the universe in a few seconds than our sun expends over the course of its life.
They happen at the birth of black holes, when a supermassive star collapses and releases powerful jets of matter that can be seen millions of light years away. An animation below shows how this works:
Their brightness allows scientists to observe these bursts “all the way back to the first stars,” O’Connor said.
“As we begin to investigate these really high redshift, very distant gamma-ray bursts, we can learn how stars first formed, what environment they form in, what kind of elements existed at the time, and see how this star formation has actually evolved over the course of the universe’s history,” he said.
Scientists have observed about 10,000 of these gamma-ray bursts since the 1970s. But this particular burst was relatively close, coming from a star about 2.4 million light-years away, giving us unprecedented insight into the structure of these bizarre explosions.
“It’s a vastly different event, and based on the brightness and proximity to us, we expected it to be a once-in-a-century event,” O’Connor said.
BOOT was particularly weird
We don’t directly see the explosion of gamma ray bursts. Instead, we see the gamma rays and other rays such as X-rays emanating from the jet of hot gas released by the explosion, and we are usually only lucky to see if they are aimed directly at our planet.
The jet itself is usually over in seconds, but scientists can capture the afterglow, which drags stellar material behind it. This fades quickly, but the BOOT’s afterglow lingered much longer than usual, confusing scientists.
A new analysis studying the explosion, published in the peer-reviewed journal Science Advances, explains why.
Scientists typically thought these jets were always “shaped like ice cream cones,” Alexander van der Horst, an associate professor of physics at George Washington University and a co-author of the study, said in a news release.
This means they tend to be compact and highly focused, spreading neatly throughout the universe, with the afterglow trailing behind the first wave.
But the new analysis suggests the BOAT jet was sloppier, spreading out from a “narrow core with wider, slanted sides,” NASA said in a press release.
“Our work clearly shows that the gamma-ray burst had a unique structure, with observations gradually revealing a narrow jet embedded in a wider gas outflow where an isolated jet would normally be expected,” said Hendrik Van Eerten, a physicist at the University of Groningen. from Bath. and study co-author, said in a news release.
BOAT undermined expectations
What scientists think happened is that as the jet was expelled, it mixed with stellar material that interfered with the outflow.
“The only way to produce a different beam structure and vary the energy is to vary some property of the exploded star, such as its size, mass, density or magnetic field,” said Eleonora Troja, a professor of physics. at the University of Rome, who led NuSTAR’s observations of the event.
“That’s because the jet essentially has to force its way out of the star. So the amount of resistance it encounters could therefore potentially affect the jet’s characteristics.”
This is “exciting” because “we can’t study the star that caused this event; it’s gone now. But we now have some data that gives us clues to how it exploded,” said O’Connor, who was an author of this study.
The analysis shows that the most extreme explosions fall short of the standard physics adopted for normal gamma-ray bursts, he said.
Van Eerten agrees: “Our model not only helps to understand the BOOT, but also to understand previous luminosity record holders that baffled astronomers about their lack of jet signature.
Still, according to O’Connor, this finding is “a huge step forward in our understanding of gamma-ray bursts,” the “equivalent Rosetta stone of long GRBs.”
O’Connor expects BOAT to yield even more discoveries, as the afterglow is predicted to remain visible to scientists for at least another year.
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