Astronomers believe they have observed a “dirty fireball” explosion for the first time, originating from a dying star. This discovery may enhance our understanding of how massive stars perish.

When a colossal star exhausts its fuel, it collapses and can explode in various forms. For instance, a collapsing black hole may emit a jet of intense radiation that penetrates the star, resulting in a brief but powerful burst of high-energy light known as a gamma-ray burst.

These gamma-ray bursts are among the most explosive events in the universe, with their energy output equivalent to that of multiple small stars like the Sun over their entire lifespan. However, astronomers remain uncertain about the exact mechanisms behind this phenomenon and how variations among massive stars impact these jets.

Researchers theorize that if a jet is contaminated with denser materials from the star, such as protons or neutrons, it might produce different emissions. These heavy particles can absorb energy, causing the jet to emit X-rays instead of gamma rays. Up until now, this “dirty fireball” scenario has not been documented.

Wang Xiang Yu and his team at Nanjing University, China, utilized the innovative Einstein Probe space telescope to capture an X-ray flash named EP241113a that aligns with the dirty fireball hypothesis.

The team detected a bright flash emanating from a galaxy approximately 9 billion light-years away. This flash contained energy similar to that of a gamma-ray burst, but interestingly, it emitted X-ray frequencies instead. The initial explosion transitioned into a glow that persisted for several hours, eventually tapering off, akin to what is observed in standard gamma-ray bursts.

“This discovery holds tremendous potential,” states Laana Starling from the University of Leicester, UK. “[Dirty fireballs] have been theorized since the 1990s, yet conclusive evidence has been lacking.”

While thousands of gamma-ray bursts have been cataloged, the event leading to this particular observation could differ fundamentally from the others, posits Stirling. It may involve a black hole or neutron star interacting with the jet in profound ways. “If a black hole is involved, it could provide a more comprehensive understanding of black hole formation throughout the cosmos,” she adds.

This finding suggests that the gamma-ray bursts commonly detected may be a result of observational biases, indicating that numerous other similar or less intense outbursts could exist, according to Gavin Lamb from Liverpool John Moores University, UK. “There’s a significant possibility this activity will persist until the jets diminish.”

Nevertheless, he is cautious about confirming it as a dirty fireball, as noted by Om Sharan Salafia from Brera Observatory, Italy. “We first need to verify if the explosion indeed originated from as distant a galaxy as Wang’s team suggests. If all these factors hold true, then this transient event certainly presents intriguing puzzles,” he concludes.