June 2, 2023

Brightest-ever gamma ray burst (the “BOAT”) continues to puzzle astronomers

Brightest-ever gamma ray burst (the “BOAT”) continues to puzzle astronomers
Brightest-ever gamma ray burst (the “BOAT”) continues to puzzle astronomersBrightest-ever gamma ray burst (the “BOAT”) continues to puzzle astronomers

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On October 9, 2022, Swift’s X-Ray Telescope captured the afterglow of the brightest gamma-ray burst ever recorded, called GRB 221009A.

On the morning of October 9, 2022, multiple space-based detectors picked up a powerful gamma-ray burst (GRB) passing through our Solar System, sending astronomers around the world scrambling to train their telescopes on that part of the sky to collect vital data on the event and its aftermath. Dubbed GRB 221009A and deemed likely to be the “birth cry” of a new black hole, the gamma-ray burst is the most powerful yet recorded. That’s why astronomers nicknamed it the BOAT, or Brightest Of All Time.

The event was promptly published in the Astronomer’s Telegram, and we now have new data from follow-up observations in several new papers published in a special focus issue of the Astrophysical Journal Letters. The findings confirmed that GRB 221009A was indeed the BOAT, appearing especially bright because its narrow jet was pointing directly at Earth. “It’s probably the brightest event to hit Earth since human civilization began,” Eric Burns, an astronomer at Louisiana State University, told New Scientist. “The energy of this thing is so extreme that if you took the entire sun and you converted all of it into pure energy, it still wouldn’t match this event. There’s just nothing comparable.”

But the various analyses also yielded several surprising results that puzzle astronomers and may lead to a significant overhaul of our current models of gamma ray bursts. For instance, a supernova should have occurred a few weeks after the initial burst, but astronomers have yet to detect one. Radio data from observations of the afterglow didn’t match predictions of existing models, and astronomers detected rare extended rings of X-ray light echoes from the initial blast in distant dust clouds.

As we’ve reported previously, gamma-ray bursts are extremely high-energy explosions in distant galaxies lasting between mere milliseconds to several hours. There are two classes of gamma-ray bursts. Most (70 percent) are long bursts lasting more than two seconds, often with a bright afterglow. These are usually linked to galaxies with rapid star formation. Astronomers think that long bursts are tied to the deaths of massive stars collapsing to form a neutron star or black hole (or, alternatively, a newly formed magnetar). The baby black hole would produce jets of highly energetic particles moving near the speed of light, powerful enough to pierce through the remains of the progenitor star, emitting X-rays and gamma rays.