Astronomers Uncover Evidence of the Universe's Earliest Stars from Hours-Long Explosion

Astronomers have made an extraordinary discovery and have learned a bit more about our universe's earliest stars because of it. They've analyzed a long-lasting blast of high-energy light seen in 2013 with features that are strikingly similar to those expected from an explosion of the earliest stars. This could validate ideas about a recently identified class of gamma-ray burst and could serve as a stand-in for what future observatories might see as that last acts of first stars.

"One of the greatest challenges of modern astrophysics has been the quest to identify the first generation of stars to form in the universe, which we refer to as Population III stars," said Luigi Piro, the lead scientist of the new study, in a news release. "This important event takes us one step closer."

Gamma-ray bursts (BRBs) are the most luminous explosions in the universe. The blasts emit both gamma rays and X-rays, and can produce rapidly fading afterglows that can be observed in visible light. This means that astronomers can detect these bursts with the help of instruments, such as NASA's Swift satellite.

This latest burst, called GRB 120925A, was first detected by the Swift's Burst Alert Telescope from a source in the constellation Fornax. Yet what was so interesting about this burst was that it was eventually localized to a galaxy so far away that astronomers realized the light had been traveling for 3.9 billion years. That's longer than the oldest evidence for life on Earth.

"GRB 120925A is a member of a rare and newly recognized class we call ultra-long bursts," said Eleonora Troja, a member of the study team. "What really sets it apart is its unusual X-ray afterglow, which provides the strongest case yet that ultra-long GRBs come from stars called blue supergiants."

The findings reveal a bit more about the early stars in the universe. More specifically, GRB 120925A probably heralded the death of a metal-poor blue supergiant, which is a model that likely characterizes the entire ultra-long class.

The findings are published in The Astrophysical Journal