Space scientists have revealed a gamma-ray burst that occurs once every 10,000 years and was 70 times brighter than any yet seen.
Gamma-ray bursts (GRB) are the most powerful class of explosions in the universe.
The GRB 221009A was first reported when NASA’s Neil Gehrels Swift Observatory detected X-rays on October 9, 2022. While the source initially appeared to be located in the Milky Way galaxy, not far from the galactic center, and data from Swift and NASA’s Fermi Gamma-Ray Space Telescope soon suggested it was much further away.
Observations from the European Southern Observatory’s Very Large Telescope then pinpointed the burst to a much more distant galaxy that happened to be behind our own. AGRB 221009A created a pulse of intense radiation swept through the solar system so exceptional that astronomers quickly dubbed it the BOAT — the brightest of all time.
“GRB 221009A was likely the brightest burst at X-ray and gamma-ray energies to occur since human civilization began,” said Eric Burns, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge.
After analyzing some 7,000 GRBs — mostly detected by NASA’s Fermi Telescope and the Russian Konus instrument on NASA’s Wind spacecraft — he established that such an event this bright may occur only once in every 10,000 years.
Further calculations show that GRB 221009A lasted for a few seconds, and the blast deposited around a gigawatt of power into Earth’s upper atmosphere. That is the equivalent of a terrestrial power station’s energy output.
“So many gamma rays and X-rays were emitted that it excited the ionosphere of the Earth,” said Erik Kuulkers, ESA Project Scientist for Integral, one of the spacecraft that detected the GRB.
A number of other ESA spacecraft, XMM-Newton, Solar Orbiter, BepiColombo, Gaia, and SOHO, also detected the GRB or its effects on our galaxy. The event was so bright that even today the residual radiation, known as the afterglow, is still visible and will remain so for a long time yet, space scientists said.
“We will see the afterglow of this event for years to come,” said Volodymyr Savchenko, University of Geneva, Switzerland, who is currently analyzing the data from ESA’s INTEGRAL observatory.
The burst was so bright it effectively blinded most gamma-ray instruments in space, which means they could not directly record the real intensity of the emission.
US scientists were able to reconstruct this information from the Fermi data. They then compared the results with those from the Russian team working on Konus data and Chinese teams analyzing observations from the GECAM-C detector on their SATech-01 satellite and instruments on their Insight-HXMT observatory.
Scientists gathered a large amount of data from entirely different instruments to understand how the original explosion took place, and how the radiation interacted with other matter on its journey through space.
They have detailed their findings in a focus issue of The Astrophysical Journal Letters, and also presented it during a press briefing at the 20th Meeting of the High Energy Astrophysics Division of the American Astronomical Society (AAS) in Hawaii, US.
