Observatories around the world have just detected a colossal burst of highly energetic radiation described as “record“.
The event, first spotted on October 9, was so bright that it was initially mistaken for an event closer to home. Originally named Swift J1913.1+1946, it was thought to be a brief X-ray flare from a not-too-distant source. Only through further analysis did astronomers discover the true nature of the glow – a gamma-ray burst, one of the most violent bursts in the Universe, now renamed GRB221009A.
Although farther away, it was still one of the closest we’ve seen to date, just 2.4 billion light-years away. Furthermore, this extremely bright gamma-ray burst appears to be the most energetic ever detected, with a velocity of up to 18 teraelectronvolts.
To be clear, while this proximity happens to be 20 times closer than the average large gamma-ray burst, it poses absolutely no danger to life on Earth.
Rather, it’s extremely exciting – a fact that could shed new light (pun intended) on these exciting explosions. Although its proximity makes it appear brighter in our sky, GRB221009A is probably the most intrinsically bright gamma-ray burst we’ve ever seen.
“This is indeed a very exciting event!” Astronomer and transient expert Gemma Anderson from the Curtin University hub of the International Center for Radio Astronomy Research (ICRAR) in Australia tells ScienceAlert.
“This fact that it is so close but also very energetic means that the radio, optical, X-ray and gamma-ray light it produces is extremely bright and therefore easy to observe. Therefore, we can study this GRB with many large and small telescopes around the world and collect very comprehensive data sets as it first brightens and then fades.”
On 2022-10-10 I observed the optical afterglow of the extremely bright GRB 221009A = Swift J1913.1+1946 from a distance using the Burke-Gaffney Observatory telescope @smubgobs.
Image: 12x300s stack, Ic filter.
More info: https://t.co/sjocA0PCOo@Astroguyz @El_Universo_Hoy pic.twitter.com/mSCKWZzkuI
— Филипп Романов/Filipp Romanov (@romanov_filipp) October 10, 2022
Gamma radiation is the most energetic form of light in the Universe, produced by the radioactive decay of atomic nuclei. And a gamma-ray burst is a massive event, discharging in a few seconds as much energy as the Sun would produce in 10 billion years. These explosions mark the end of the life of a massive star – a supernova or supernova. They can also emerge from a collision between two neutron stars.
Basically, when a star more massive than about eight of our Suns squeezed together runs out of material to fuel its hydrogen fusion, the outward pressure drops and the star collapses under gravity. This causes a colossal explosion (the supernova), propelling the outer material into space, while the core collapses into a neutron star or black hole.
Different gamma-ray burst profiles mean different kinds of bursts, which decay in different ways. When astronomers observed a collision between two neutron stars in 2017, it produced a brief burst of gamma rays. Long bursts are associated with unusually powerful events, ultraluminous supernovae and supernovae.
It’s not yet clear what we’re looking at with GRB221009A.
“It’s still too early to tell,” Anderson says. “The light from an underlying supernova will take days to shine through. However, given the long duration of this gamma-ray burst, it can be a very powerful type of supernova.”
What we do know is that the explosion appears to have come from a very dusty galaxy and that it was very powerful. And the Large High Altitude Air Shower Observatory (LHAASO), a Cherenkov observatory in China, has detected photons with energies up to about 18 teraelectronvolts (TeV). To date, only a few gamma-ray bursts have been detected with emission in the TeV range. If the LHAASO data is verified, GRB221009A will be the first above 10 TeV.
There is, for now, a lot of science to be done in the days after the outbreak. Scientists are training telescopes at the object’s location to observe the behavior of the afterglow at as many wavelengths as possible, information crucial to uncovering the cause of the explosion in detail.
“When you’re dealing with cosmic explosions that eject stellar debris at near the speed of light, leaving behind a black hole, you’re watching physics happen in the most extreme environments that are impossible to recreate on Earth,” Anderson says.
“We still don’t fully understand this process. Such a close explosion means we can collect very high-quality data to study and understand how such explosions happen.”