Unexplained Cosmic Signal Detected: What Scientists Are Discovering From Beyond Our Galaxy

Gamma ray bursts (GRBs) are among the most intense explosions in the universe. They release more energy in seconds than our Sun will emit over its entire 10-billion-year life. Usually, these bursts come from dying stars that explode in a supernova. However, an extraordinary new case has grabbed astronomers’ attention: a GRB that repeated multiple times in just one day, as if the star experienced successive deaths.

Antonio Martin-Carrillo, an astronomer at University College Dublin, called this event “unlike any other seen in 50 years of GRB observations.” He co-authored a study in The Astrophysical Journal Letters detailing this unusual detection.

Typically, a GRB occurs just once since the source is completely destroyed in the explosion. Yet, this new burst, labeled GRB 250702B, challenges that notion. The European Southern Observatory noted how this phenomenon defies explanation: how can a star explode multiple times?

To understand this, let’s look at how stars die. When a massive star runs out of fuel, it collapses under its own gravity, leading to a supernova that scattered its remains. However, not all supernovas behave the same way. In systems with a white dwarf—an unusually dense star—and a regular star, material can be pulled from the companion star. If enough builds up on the white dwarf, it triggers a massive explosion.

Astronomers have previously observed stars exploding multiple times in similar binary systems, but only once resulted in a full-fledged supernova. The latest event is different. Detected on July 2 by NASA’s Fermi Gamma-ray Space Telescope, GRB 250702B showed three distinct bursts over a single day, and the Einstein Probe X-ray telescope captured activity a day earlier.

“This is 100-1000 times longer than most GRBs,” said Andrew Levan from Radboud University, highlighting its uniqueness. This event appears periodic, which is unprecedented.

Initially, scientists thought the burst originated from the Milky Way. However, further observation with the HAWK-I infrared camera on the Very Large Telescope in Chile suggested the source is actually billions of light-years away. This distance indicates a more powerful explosion than originally suspected.

Martin-Carrillo speculates that this could stem from a massive star collapsing. Yet, this scenario typically results in a short-lived GRB. “If this is a massive star, it’s a collapse unlike anything we’ve ever witnessed,” he noted. Another possibility could be a tidal disruption event, where a black hole tears apart a star. But this would require an unusual combination of star and black hole types.

Interestingly, some astronomers believe the black hole involved may be an intermediate-mass black hole, a rare and unobserved type that falls between typical stellar black holes and supermassive black holes. This “mass gap” remains a mystery in astrophysics.

Mysteries abound surrounding GRB 250702B. While we may not fully understand its origins, this discovery marks significant progress. Martin-Carrillo concluded, “We are still not sure what produced this or if we can ever really find out, but we’re taking huge steps toward understanding such an unusual event.”

More on astronomy: Scientists Discover Black Hole Created Less Than One Second After the Big Bang

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Gamma ray bursts, Antonio Martin-Carrillo, University College Dublin, white dwarf, European Southern Observatory, spectacular supernova, GRB observations, stellar object