What is the most recent gamma-ray burst?

On the morning of October 9, astronomers’ inboxes pinged with a relatively modest alert: NASA’s Swift Observatory had just detected a fresh burst of energy, assumed to be coming from somewhere within our own galaxy. But six hours later—when scientists realized an instrument on the Fermi Space Telescope had also flagged the event—another more pressing email arrived. “We believe that this source is now likely a gamma-ray burst,” it read. “This would suggest a highly energetic outburst, and therefore we strongly encourage follow-up.” In other words, this was a career-making chance to catch a rare celestial event in real time.

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Astronomers around the world sprang into action. They were eager to point their telescopes at this powerful, jetted explosion of the most energetic photons in our universe. “And by jetted, I mean like a firehose of emission,” says Wen-fai Fong, an astrophysicist at Northwestern University. Blasts like this are thought to be caused by the supernovae of giant stars, destructive collapses that give birth to black holes. The burst, dubbed GRB 221009A, went off about 2 billion light years away in the Sagitta constellation—one of the closest and most energetic ever observed—and it’s likely that one of the jets was fortuitously pointed directly at Earth. Together, these factors made for a flash at least 10 times brighter than all the others spotted in the three decades since such bursts were discovered, leading some astronomers to dub it the “BOAT”—brightest of all time.

“I kept thinking, is this real? Because if it is, it’s an extremely rare, once-in-a-lifetime type of event,” Fong says. She and others are in the thick of collecting data that they hope will confirm that the rays actually came from a supernova, and help them isolate which stellar properties led to such an energetic explosion and how much of the collapsing material got spat out by the infant black hole. (Theoretical musings have already started appearing on the arXiv preprint server.)

While detecting supernovae is now fairly common, it’s rarer to catch one in conjunction with a gamma-ray burst—they’re usually too faint to show up because they are so far away, and only a fraction of supernovae actually generate these explosions. But since this burst was so intense, scientists expect to see the supernova very clearly. “It’s really reinvigorated the community,” Fong says. “Everyone who has a telescope, even if they don’t normally study gamma-ray bursts, is trying to point their detectors at this to get the most complete dataset that we can.”

Gamma rays from the blast were recorded for several hundred seconds. Next came a slew of lower energy photons, including x-rays, optical and infrared light, and radio waves. It’s this afterglow that astronomers at ground-based telescopes are hungry to capture, because observing how the influx of photons changes over time will help them characterize the types of stars producing such bursts, the mechanisms driving these explosions, and the resulting environments they produce. These insights could shed light on what influence gamma-ray bursts have on future generations of stars, and determine whether stellar deaths make life possible for us on Earth by producing the heavy elements that can heat a planet’s interior and help sustain its magnetic field.

Because the emission spans nearly all wavelengths of light, many different instruments can observe it, which has turned the gamma-ray burst postmortem into a global scientific event. Orbiting satellites like NASA’s NuSTAR are measuring its high energy x-rays, while sites like the Australia Telescope Compact Array are collecting the burst’s radio emission. “If we don’t get data one night, we can pretty much guarantee that someone will,” says Jillian Rastinejad, a Northwestern graduate student working with Fong. Together, they’re spearheading observations of visible light from the burst using the Gemini South telescope in Chile, data that will be supplemented by measurements from the Lowell Discovery Telescope in Arizona, South Korea’s Bohyunsun Optical Astronomy Observatory, and India’s Devasthal Fast Optical Telescope. Even the James Webb Space Telescope got in on the action, as scientists reported the afterglow observed in infrared last Friday.

A fleet of space telescopes unexpectedly detected the record-breaking gamma-ray burst GRB221009A onOct.9, sparking concern among spacecraft operators about the blast's odd signal. 

The European Space Agency's (ESA) Gaia galaxy mapper sent a strange reading to its controllers on early afternoon, Oct. 9, showing a surprising amount of high-energy particles hitting the spacecraft's detectors. The engineers were puzzled for a while, ESA said in a statement (opens in new tab), but eventually realized that the spacecraft, built to measure precise positions of stars in our galaxy, detected the powerful gamma-ray burst GRB221009A which flashed at Earth from a distant world over 2 billion light-years away. 

Other ESA spacecraft picked up the signal, described as the most energetic gamma-ray burst ever detected, among them the sun-exploring Solar Orbiter and Mercury-bound BepiColombo. The data, ESA said in the statement, is still being analyzed.

Related: Astronomers just spotted the most powerful flash of light ever seen

ESA's probably best catch is an image of the gamma-ray burst's immediate aftermath taken by the agency's veteran spacecraft XMM-Newton, which, just like NASA's Swift observatory that spotted GRB221009A first, specializes in detecting high-energy X-ray radiation. 

XMM-Newton, in orbit since 1999, captured the mesmerizing rings around the source of the burst that are a result of the interaction between the energetic rays and the dust in our galaxy. 

ESA's gamma-ray observatory Integral, which celebrated 20 years in orbit earlier this month, imaged the waning source one day after the explosion, clearly detecting a still active region.

Data gathered by the satellites will help astronomers to learn all there is about this event, which has since been described as a "once-in-a-century" by astronomers.

Gamma-ray bursts are the most energetic explosions known to occur in the universe apart from the Big Bang. Astronomers believe that these bursts mark the birth of black holes in supernova explosions of extremely massive stars. As a vast amount of material from the old collapsing star falls into the new-born black hole, the black hole gets rid of some of it in the form of a powerful jet that bursts into the surrounding space at nearly the speed of light. The jet is rather narrow and therefore the burst can be detected only in the parts of the universe where it aims. 

Satellites around Earth detect about one gamma-ray burst per day but only in about 30% cases can astronomers locate the burst's source. GRB221009A, however, was like none seen before, the energy of its photons temporarily blinding the sensitive gamma-ray detectors on specialist satellites. 

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