The most powerful class of explosions in the universe—a gamma-ray burst—reached the solar system on Sunday, Oct. 9, 2022. It was 70 times brighter than any yet seen. A telescope on the International Space Station sensed it. So did NASA’s Fermi Gamma-ray Space Telescope and scores of satellites. It was even detected by the Voyager 1 probe now in interstellar space.
The subject of a special edition of The Astrophysical Journal Letters this week, this pulse of intense radiation has been called the “BOAT”—the brightest of all time—but what was it?
“GRB 221009A was likely the brightest burst at X-ray and gamma-ray energies to occur since human civilization began,” said Eric Burns, LSU Department of Physics and Astronomy assistant professor. He led research into about 7,000 gamma-ray bursts and concluded that events like GRB 221009A occur roughly once in every 10,000 years.
Gamma-ray bursts are thought to originate in supernovas—the explosion of a single star—but this one was exceptional in that it was both more powerful than any other and no bright supernova star was seen in the days and weeks after.
“If it’s there, it’s very faint. We plan to keep looking,” said Andrew Levan, a professor of astrophysics at Radboud University in Nijmegen, Netherlands. The search is underway with both the James Webb Space Telescope and the Hubble Space Telescope for the supernova, but there is another possible explanation.
“It’s possible the entire star collapsed straight into the black hole instead of exploding,” said Levan. It’s thought that gamma-ray bursts are jets of particles accelerated into space at near-light speed that rip through the remains of a collapsed massive star—and signal the birth of a back hole.
It raises an intriguing cosmic question. “We think of black holes as all-consuming things, but do they also return power back to the universe?” asked Michela Negro, an astrophysicist at the University of Maryland, Baltimore County, and NASA’s Goddard Space Flight Center in Greenbelt.
The jets of intense radiation sensed by spacecraft in October traveled for around 1.9 billion years, but it was the angle at which it arrived that may explain its brightness, suggest the researchers. The jets were very narrow and one was pointed directly at Earth. That may explain its incredible brightness.
The research team included astronomers from the UK, USA, Australia, the Netherlands, Italy, and South Africa using data from radio telescopes across the world and the solar system.