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NASA’s Fermi gamma-ray space telescope probed the most powerful explosion since the Big Bang, discovering a feature never seen before. The feature could be the result of matter and antimatter particles being ejected at 99.9% the speed of light.
The burst was an example of a gamma-ray burst (GRB); when it was first observed on October 9, 2022, by NASA’s Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory, it was designated GRB 221009A. The GRB’s power was soon revealed, earning it the nickname of the Brightest Of All Time or the “BOAT.”
“As far as we’ve been able to detect GRBs, there’s no question that this GRB is the brightest we’ve ever seen by a factor of 10 or more,” Wen-fai Fong, associate professor of physics and astronomy and leader on. The Fong Group at Northwestern and one of the discoverers of the BOAT explained that around the time it was considered so bright.
Scientists theorize that the BOAT was launched by a supernova explosion that accompanied the death and collapse of a giant star that was located about 2.4 million light years away. This incident probably left a black hole behind.
Related: Scientists identify the origin of the ‘BOAT’ – the brightest cosmic explosive ever
“A few minutes after the BOAT erupted, the Fermi Gamma-ray Burst Monitor recorded an unusual energy peak that caught our attention,” research leader Maria Edvige Ravasio of Radboud University said in a statement. “When I first saw that signal, it gave me goosebumps. Our analysis since then shows that it is the first high-confidence emission line ever seen in 50 years of studying GRBs.”
What did Fermi find in the BOAT?
The first gamma-ray burst was observed in 1967 by the US Vela satellites; it was officially documented two years later, then revealed to the public in 1973.
Since then, scientists have detected an abundance of GRBs, determining that these brief flashes of light have a cosmic origin and are the most powerful and violent explosions in the known universe. The most common type of GRB occurs when stars with at least eight times the mass of the Sun run out of the fuel needed for nuclear fusion in their cores and can no longer act on the pull of their own gravity ; therefore their hearts fell. This creates a spinning black hole that sends matter to its poles, exploding out as jets traveling at close to the speed of light.
When these jets aim directly at Earth, we see them as GRBs.
GRBs are so powerful that if one erupted within a few thousand light years of Earth, it could destroy life on our planet by disrupting or destroying the atmosphere. However, even in the midst of all these terrible events, the BOAT stood out almost immediately.
The scientists finally determined, using statistics for other observed GRBs, that an event as powerful and bright as the BOAT would appear in the sky above Earth exactly once every 10,000 years. They also discovered that, despite occurring 2.4 billion light years away, the BOAT had an effect on the Earth’s atmosphere.
On October 9, 2022, high-energy gamma-ray light from BOAT saturated most of the gamma-ray detectors in orbit, including those on board Fermi. This prevented the true power of the blast from being measured at its peak. However, about five minutes after the BOAT was spotted, it slowed down enough to allow Fermi to see it again. NASA’s gamma-ray telescope spotted a strange feature in its light, or “spectrum,” called a “putative emission line.”
When light passes through the material, because elements absorb and emit light at specific frequencies, they leave absorption and emission “fingerprints” on this light. This means that scientists can reconstruct the elements that this light passed through and determine the chemical composition of the elements that it interacted with.
“Although some previous studies have reported possible evidence of absorption and emission features in other GRBs, subsequent scrutiny has shown that these may all be statistical fluctuations. What we see in the BOAT is different,” team member Om Sharan Salafia of the INAF- Brera Observatory in Milan, the statement said. “We have determined that the odds that this feature is just a noise fluctuation is less than one chance in half a billion.”
The emission line that Fermi saw in the light from the BOAT lasted for about 40 seconds, reaching a peak energy of 12 million electron volts (MeV). The energy of light in the visible region of the electromagnetic spectrum is between two and three electron volts (eV).
The researchers think they know what caused this feature. Every particle of matter has an antimatter particle “twin.” When these particles meet, they annihilate, releasing their energy back into the universe. The spectral feature the team saw in the BOAT could come from electrons and their antimatter equivalent, positrons, annihilating.
“When an electron and a positron collide, they annihilate, producing a pair of gamma rays with an energy of 0.511 MeV,” team member Gor Oganesyan of the Gran Sasso Science Institute said in the statement. “Because we are looking into the jet, where matter is moving at close to the speed of light, this emission becomes blueshifted and pushed towards much higher energy.”
If the team is correct, the particles must have been traveling at about 99.9% of the speed of light before they annihilated each other.
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“After years of studying these incredible cosmic explosions, we still don’t understand the details of how these jets work,” team member Elizabeth Hays, a Fermi project scientist at NASA’s Goddard Space Flight Center, said in the statement . “Looking for tips like this is great.”
The team’s research was published Friday (July 26) in the journal Science.
