A space explosion detected this summer burned for days on end, making it the longest and most unusual gamma-ray burst ever seen.
Gamma-ray bursts are the universe’s most powerful explosions. They usually flare for just seconds or minutes, triggered when massive stars collapse or when ultra-dense dead stars called neutron stars collide. But this particular event — known as GRB 250702B — defied all expectations.
Satellites, including NASA’s Fermi and Swift telescopes, along with instruments on other spacecraft, spotted the explosion on July 2. No single observatory could track the full event, so scientists stitched together data from multiple sources to capture the entire outburst.
Researchers think the long, record-breaking explosion may reveal a new way black holes destroy stars — something not covered by existing theories — putting this gamma-ray burst in a league of its own.
“This is certainly an outburst unlike any other we’ve seen in the past 50 years,” said Eliza Neights, a NASA researcher based at George Washington University, in a statement.
Follow-up observations traced the burst to a galaxy about 8 billion light-years away, meaning it erupted long before Earth even existed. Images from the James Webb Space Telescope and others revealed the radiation shining through thick bands of dust, providing a rare, detailed view of the hosting galaxy.
And it definitely is a galaxy, albeit a strange one, said Andrew Levan, an astrophysics professor at Radboud University in the Netherlands who led the Hubble study. It’s either two galaxies merging or one really massive one with a dark band of dust dissecting its core.
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The explosion released as much energy as 1,000 suns shining for 10 billion years, all within a few days, scientists say. The initial burst of energy lasted at least seven hours — more than double any previous gamma-ray burst.
“The resolution of Webb is unbelievable,” said Huei Sears, a Rutgers University researcher who led some of the observations, in a statement. “We can see so clearly that the burst shined through this dust lane spilling across the galaxy.”
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The Neights-led gamma-ray paper will appear in the Monthly Notices of the Royal Astronomical Society journal. Other findings have already appeared in The Astrophysical Journal Letters, with more to come.
Most scientists agree the prolonged flash likely occurred when a black hole ate a star, but two other ideas can’t be ruled out yet. One involves a medium-size black hole, thousands of times heavier than the sun, tearing a wandering star apart. Gravity would stretch and rip the star before swallowing it.
Scientists used ground and space telescopes to pinpoint the galaxy where the prolonged gamma-ray burst originated in the universe.
Credit: NASA Goddard / A. Mellinger / CMU
The second scenario envisions a smaller black hole orbiting a nearby companion star. Over time, the black hole siphoned gas from its partner, then plunged into the star itself, consuming it quickly.
In both cases, gas stripped from the star swirled into a superheated disk around the black hole. As material fell inward, the system fired narrow jets of energy at nearly the speed of light — jets responsible for the gamma-ray glow detected from Earth.
The event broke other norms. X-rays appeared a full day before the main burst and continued flaring for two days after, behavior never seen in typical gamma-ray bursts. Astronomers also detected no clear supernova, the bright explosion usually left behind by collapsing stars.
Those peculiar details strengthen the idea that scientists may be witnessing a new type of blast. But catching more of these phenomenons will be essential to crack the case.
