Astronomers detect “mysterious explosion” coming from outside the Milky Way

SALT LAKE CITY (ABC4) — Astronomers have detected a massive gamma-ray explosion coming from outside the galaxy. The explosion’s origins and power are baffling scientists.

On July 2, 2025, astronomers were alerted to a gamma ray burst, the most powerful explosion in the cosmos. The burst was pinpointed to outside the Milky Way galaxy by the European Southern Observatory’s Very Large Telescope (VLT).

Scientists say there are no known scenarios that explain the source of the burst, which is believed to have lasted 100 to 1,000 times longer than most gamma ray bursts.

Tanmoy Laskar, a professor in the University of Utah’s Department of Physics and Astronomy recently co-authored a study of the event. Laskar says the burst’s long duration was different.

“This immediately alerted us to the unusual nature of this explosion,” Laskar said.

Scientists say that unlike most gamma ray bursts — normally caused by dying stars — this burst exhibited repeated bursts over the course of an entire day. Normally such bursts last just minutes.

“The fact that this object is extragalactic means that it is considerably more powerful,” Antonio Martin-Carrillo, an astronomer at University College Dublin Ireland, said of the event, adding that the size suggests it may be located a few billion light-years away.

The study was published in The Astrophysical Journal Letters and pulled from observations from the VLT, the Hubble Space Telescope, the James Webb Space Telescope, the Fermi Gamma-Ray Space Telescope, and the Einstein Probe.

More observations are needed to understand the anomaly.