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Mysterious 10-minute X-ray burst from a distant galaxy may have come from 2 dead stars colliding
"When I saw the X-ray data from this new event, I realized something was up."
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Astronomers investigating mysterious flashes of X-rays believe that these blasts could stem from collisions between neutron stars, the events that forge elements like gold, silver, and platinum.
The event designated EP250704a, was first seen on July 4, 2025, as a blast of gamma rays lasting half a second followed by a bright X-ray emission lasting 10 minutes. After receiving an alert from the joint European-Chinese Einstein probe that witnessed the blast, a team of astronomers started to hunt for its cause by studying the aftermath of the explosion using the European Southern Observatory's Very Large Telescope (VLT), the Very Large Array (VLA), and other telescopes.
According to astronomer Niccolò Passaleva who led the observations of the X-ray flash with the VLT, this cosmic outburst was unlike any scientists had seen before. "This is the longest-lasting prompt X-ray flash ever observed from a neutron star merger," Passaleva said in a statement. "It is an opportunity to have a front-row seat to the most extreme forces of the universe and discover more of its secrets."
Neutron stars are created when massive stars die in supernova explosions, cramming one or two the mass of the sun into a width akin to a city on Earth and creating material so dense that a single teaspoon of neutron star matter brought to Earth would weigh 10 million tons. When these extreme dead stars slam together, they create environments so turbulent and violent they are capable of forging elements so heavy that even the hearts of stars can't do it. Elements like the gold on your finger.
These collision and merger events, marked by flashes of light called kilonovas, have long been associated with flashes of high-energy gamma-rays that disappear within two seconds, but new research suggests some neutron star mergers could reveal themselves via blasts of X-rays lasting minutes.
In particular, scientists have wondered if neutron star mergers could be the cause of hundreds of X-ray flashes in distant galaxies discovered by the Einstein probe since its launch in 2024. While some of these have been linked to the supernova-explosive death of massive stars that can create a neutron star or a black hole, others have defied explanation. EP250704a is one such X-ray flash.
"When I saw the X-ray data from this new event, I realized something was up," team member Eleonora Troja, part of the Einstein Probe European collaboration, said in the statement.
The team believes that there is something special in the neutron star merger mix that results in these X-ray bursts.