Artist's visualization of GRB 221009A showing the narrow relativistic jets (emerging from a central black hole) that gave rise to GRB and the expanding remains of the original star ejected through the supernova explosion – AARON M. GELLER / NORTHWESTERN / CIERA
April 12 () –
In October 2022, an international team of researchers observed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A.
Now, a team led by Northwestern University has confirmed with the James Webb Space Telescope (JWST) that the phenomenon responsible for the historic outbreak, called BOAT (brightest of all time) It is the collapse and subsequent explosion of a massive star.
While this discovery solves a mystery, another mystery deepens. Researchers speculated that within the newly discovered supernova there could be evidence of heavy elements, such as platinum and gold. The extensive search, however, did not find the signature that accompanies said elements. The origin of heavy elements in the universe remains one of the biggest open questions in astronomy.
The research is published in the journal Nature Astronomy.
“When we confirmed that the GRB was generated by the collapse of a massive star, that gave us the opportunity to test a hypothesis about how some of the heaviest elements in the universe form,” said Northwestern's Peter Blanchard, who led the study.
“We saw no signatures of these heavy elements, suggesting that extremely energetic GRBs like BOAT do not produce these elements. That doesn't mean that all GRBs don't produce them, but it is a key piece of information as we continue to understand where these heavy elements come from. Future observations with Webb will determine whether the 'normal' BOAT cousins produce these elements.”
When its light covered Earth on October 9, 2022, BOAT was so bright that it saturated most of the world's gamma ray detectors. The powerful explosion occurred about 2.4 billion light years from Earth, in the direction of the constellation Sagittarius, and lasted a few hundred seconds. As astronomers raced to observe the origin of this incredibly bright phenomenonthey immediately felt amazed.
“The event produced some of the highest energy photons ever recorded by satellites designed to detect gamma rays,” Blanchard said. “This was an event that Earth sees only once every 10,000 years. We are lucky to live in a time when we have the technology to detect these explosions occurring throughout the universe. “It is very exciting to observe an astronomical phenomenon as rare as BOAT and work to understand the physics behind this exceptional event.”
Instead of observing the event right away, Blanchard, her close collaborator Ashley Villar of Harvard University, and their team wanted to see the GRB during its later phases. About six months after GRB was initially detected, Blanchard used JWST to examine its consequences.
“The GRB was so bright that it obscured any potential supernova signatures in the first weeks and months after the explosion,” Blanchard said. “At those times, the so-called glow of the GRB was like the headlights of a car coming directly at you, preventing you from seeing the car itself. Therefore, we had to wait for it to fade significantly to give us the opportunity to see the supernova.”
Blanchard used JWST's near-infrared spectrograph to observe light from the object at infrared wavelengths. That's when he saw the characteristic signature of elements like calcium and oxygen that are normally found inside a supernova. Surprisingly, it was not exceptionally bright, like the incredibly bright GRB that accompanied it.
“It's no brighter than previous supernovae,” Blanchard said. “It seems pretty normal in the context of other supernovae associated with less energetic GRBs. You might expect that the same collapsing star that produces a very energetic and bright GRB would also produce a very energetic and bright supernova. But it turns out that's not the case.” . “We have this extremely luminous GRB, but a normal supernova.”
