Photo: National Science Foundation
Astronomers believe a mysterious X-ray burst detected in space may have originated from the collision of two neutron stars, an event capable of producing heavy elements such as gold, silver and platinum, Space.com reports.
The event, designated EP250704a, was first detected on July 4, 2025, as a gamma-ray burst lasting half a second. It was followed by an X-ray burst that continued for 10 minutes.
After receiving an alert from the Einstein Probe, a joint European-Chinese space mission, astronomers investigated the event using the European Southern Observatory’s Very Large Telescope (VLT), the Very Large Array (VLA) radio telescope and other instruments.
Astronomer Niccolò Pessa, who led the VLT observations, said the event was unlike anything scientists had previously observed.
“This is the longest initial X-ray burst ever detected from a neutron star merger. It is a front-row opportunity to witness the most powerful forces in the universe at work and uncover new cosmic mysteries,” he said.
Neutron stars form when massive stars die in supernova explosions. Their mass, equivalent to one or two times that of the Sun, is compressed into an object roughly the size of a city. Their density is so extreme that a teaspoon of neutron-star matter would weigh around 10 million tons on Earth.
When neutron stars collide and merge, the extreme conditions can trigger the formation of heavy elements, including gold, that cannot be produced through ordinary stellar processes.
Scientists are also investigating whether neutron star mergers could explain the hundreds of X-ray bursts detected by Einstein Probe since its launch in 2024. EP250704a was one such event.
The researchers believe that at least one magnetar — a neutron star with an exceptionally powerful magnetic field — was involved in the merger.
“If a magnetar forms after the collision, the bursts can last longer,” said Eleonora Troja, a member of the Einstein Probe collaboration. She explained that magnetars release enormous amounts of stored magnetic energy, potentially making explosions brighter and longer-lasting.
The team ruled out a supernova as the source of the X-ray burst and determined that the light from the event had traveled approximately six billion years to reach Earth.
In a separate discovery, scientists investigating an exceptionally powerful explosion detected in 2022, approximately 2.4 billion light-years away, found unexpected results when they reanalyzed the event.
