A new paper proposes that the record-setting gamma ray burst that reached Earth on Oct. 9, 2022, was so bright and so long-lasting because it originated in a star as it collapsed into a black hole.
The once-in-a-millennium blast of energy — later dubbed the Brightest of All Time (BOAT) — has continued to puzzle scientists, who say it was 70 times brighter than the second most powerful burst on record. An explanation would help to demystify the tremendous outpourings of energy, which are detectable from billions of light years away.
Where Do Gamma Ray Bursts Come From?
Scientists believe gamma ray bursts come from the formation of black holes, especially those that form when massive stars run out of fuel and collapse in on themselves.
Great jets of energy — including gamma rays, the highest-energy form of light — shoot their way out of the star and into the universe where they gradually lose their oomph. This process happens very slowly, however, as BOAT crossed 2.4 billion light years to reach Earth over an estimated 1.9 billion years.
How Often Do Gamma Rays Burst?
Space scientists track gamma ray bursts using a small network of satellites, and when BOAT first reached them, it overwhelmed their sensors. Researchers pieced together the data in the months after, slowly making sense of the scale of the unprecedented burst, which had also disrupted Earth’s ionosphere.
Scientists initially rated the burst as something that would happen once in every 10,000 years, but the new paper says that events of this enormity occur once in every 1,000 years, meaning that they may have happened a handful of times in recorded history.
BOAT brought with it everything from low-energy radio waves to the highest energy photon ever detected from such an event, the paper says. The burst set another record for duration as the main phase lasted seven minutes instead of just a handful of seconds, as per usual. In its wake, BOAT also left behind unusual “X-ray rings” detectable by telescopes on Earth and a long afterglow.
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(Credit: ESA/XMM-Newton/M. Rigoselli/INAF)
X-ray rings scattered by dust clouds and detected by the XMM-Newton telescope.
Unique Pulse and Afterglow
Much about BOAT seemed odd — the off-the-charts burst, the extremely long afterglow, and the lack of an associated supernova. The very shape of the pulse was sloping and uneven, and so the researchers say it must have interacted with something shortly after its creation. That’s what made it into a monster.
According to Hendrik Van Eerten, an astrophysicist from the University of Bath, gamma ray burst jets “need to go through the collapsing star in which they are formed.” In BOAT’s case, the astrophysicist adds that the burst was probably intensified by “the amount of mixing that happened between the stellar material and the jet,” according to a press release.
The BOAT’s unusual shape explains much, including the long afterglow.
“The [burst] had a unique structure,” he says in a press release, “with observations gradually revealing a narrow jet embedded within a wider gas outflow.”
A Rare Opportunity
Understanding BOAT would shed light on other record-setting bursts and other areas of the cosmos, where satellites detect several gamma ray events every day (and that’s just those pointed at Earth).
“We think this is a once-in-a-thousand-year opportunity to address some of the most fundamental questions regarding these explosions, from the formation of black holes to tests of dark matter models,” says co-author Brendan O’Connor, a newly graduated doctoral student at George Washington University, in a press release.
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