This 10-minute X-ray burst possibly came from 2 colliding stars
What's the story
Astronomers have detected a mysterious flash of X-rays, which could possibly be the result of two neutron stars colliding. The event, dubbed EP250704a, was first observed on July 4, 2025. It started with a half-second-long gamma-ray burst and was followed by a bright X-ray emission that lasted for an unprecedented 10 minutes. The discovery was made possible by the joint European-Chinese Einstein probe satellite's alert system.
Investigation
'Unprecedented' cosmic outburst
Following the Einstein probe's alert, astronomers launched an investigation into the origin of EP250704a.
They examined its aftermath with multiple telescopes, including the European Southern Observatory's Very Large Telescope (VLT) and the Very Large Array (VLA).
Niccolo Passaleva, who led these observations, said this cosmic outburst was unlike anything scientists had seen before.
He called it "the longest-lasting prompt X-ray flash ever observed from a neutron star merger."
Stellar collisions
What are neutron stars and how do they form?
Neutron stars are formed when massive stars explode in supernovae, collapsing into a city-sized mass with material so dense that a teaspoon would weigh 10 million tons on Earth.
When these extreme dead stars collide, they create conditions violent enough to forge elements heavier than gold and platinum.
These collision events, known as kilonovas, have been linked to high-energy gamma-ray bursts that fade within seconds. However, some neutron star mergers might also produce X-ray bursts lasting minutes.
Unique event
One of many flashes detected by Einstein probe
EP250704a is one of the many X-ray flashes detected by the Einstein probe since its launch in 2024.
While some have been linked to supernovae, others remain unexplained.
The team behind this research thinks that there is something special in the neutron star merger mix that results in these X-ray bursts.
They also ruled out a supernova as the cause of this particular event and confirmed that light from this collision has been traveling to Earth for six billion years.
Stellar phenomena
Involvement of magnetars in merger events
The team behind this research believes that the neutron star merger involved at least one magnetar.
These are rapidly spinning neutron stars with huge magnetic fields.
When they release their magnetic power into the surroundings, it can make any explosion brighter and longer-lasting.
The discovery of more such extreme X-ray flashes could help astronomers determine how often magnetars are formed through these neutron star mergers, Passaleva said in a statement.