Failed stellar jets create mysterious X-ray bursts in space

When giant stars die, they don’t always go out with the spectacular fireworks that astronomers expect. Sometimes their last explosive jets are trapped in their own excellent remains, creating mysterious X-rays that have confused scientists for years.

A new study of the closest events ever suggested that these “failed” star explosions may be far more common than their successful counterparts.

The discovery is centered on EP 250108A, a fast X-ray transient detected by the Einstein probe satellite in January 2025. Located 2.8 billion light years away, the event provides astronomers with unprecedented front seats to watch the final moments of the dying star unfold in multiple light wavelengths.

Fast X-ray transients (FXTS) are short but powerful bursts of X-ray energy that last for a few seconds to several hours. Until recently, these cosmic flashes were still mysterious because they happened too far and disappeared to be studied in detail.

When the jet cannot escape

The international research team used telescopes, including the Gemini Observatory in Chile and the SOAR telescope, to track the evolution of EP 250108A on six critical days. The challenge they found was a conventional understanding of how the biggest superstar reached its end.

“This FXT supernova is almost a twin of the supernova of the past,” explains Rob Eyles-Ferris, a postdoctoral researcher at the University of Leicester and lead author of one of the peer research. “Our observations of early stages of EP 250108a’s evolution suggest that explosions of large stars can produce both phenomena.”

Typically, when stars collapse 15-30 times higher than our sun, they can emit jets of material at the speed of light. These jets pass through the outer layer of the star, forming a gamma-ray burst, the most powerful explosion in the universe. But in the case of EP 250108A, something went wrong.

Data show that the star’s jets are trapped in their own debris and cannot be released. When these suffocating jets interact with surrounding stellar material, they quickly slow down and convert their kinetic energy into X-ray emissions detected by Einstein’s probe.

Key research results:

• The failed jet contains approximately 0.04-0.15 solar material
• Before rapid deceleration, the initial expansion speed reaches 40-60% of the speed of light
• Progenitor cell stars may weigh 15-30 times higher than our sun
• According to the detection rate, failed jets are more common than successful jets

Solve X-ray puzzles

Analysis by the research team showed that EP 250108A represents the “Collapsar engine”, an explosion driven by materials that fall into a black hole and fire jets. However, unlike successful gamma-ray bursts, these jets are still limited to dense occasional materials.

To test this hypothesis, scientists modeled different explosion scenarios. A conventional supernova explosion will require impractical energy and high-speed materials to match observations. However, the failed jet model contains less fast material, fitting the data perfectly.

“X-ray data alone cannot tell us what the phenomenon is causing the FXT,” noted Jillian Rastinejad, a doctoral student at Northwestern University. “Our optical monitoring activity at EP 250108A is key to identifying the consequences of FXT and assembling the clues into its origins.”

A new window of budding death

As the trapped jet launch disappears, the team watches a more familiar spot: the optical glow of Supernova SN 2025kg. This type of IC wide-bushed supernova displays the characteristic features of huge stellar explosive deaths, with extensive absorption lines indicating that the material moves at speeds of thousands of kilometers per second.

These observations depict a picture of the death of a star, which is more chaotic and diverse than previously understood. Although gamma-ray bursts have become headlines for cosmic monsters, these failed jets may represent a more common reality that large stars actually expire.

FXTs have been discovered several times a month since the release of the Einstein Detection, and historically, gamma-ray bursts occur approximately once a year. This suggests that failure or weak nozzles dominate the explosive death of large stars.

This discovery has broader significance for understanding the diversity of stellar evolution and explosive cosmic events. The upcoming Vera C. Rubin Observatory’s heritage survey of space-time will provide astronomers with a wealth of time-domain data and potentially reveal more examples of these exotic stars’ deaths.

“This discovery gives a broader understanding of the diversity of deaths in large stars and requires a deeper study of the overall landscape of the entire star evolution,” Eyles-Ferris concluded.

The study shows how the rapid response ability of modern astronomy changes our understanding of transient cosmic phenomena. By capturing these brief events in real time and taking detailed observations in the electromagnetic spectrum, astronomers finally solve the mystery that has persisted for decades.

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