Astronomers puzzled by repeating gamma ray bursts outside Milky Way

The unknown phenomenon repeated several times over the course of a day, an event unlike anything ever witnessed before.

The finding is intriguing, as gamma-ray bursts (GRBs) indicate the catastrophic destruction of stars lasting milliseconds to minutes and so should not repeat, or last a day as this one did.

As the most energetic explosions in the universe, they can mean massive stars dying in powerful blasts or being ripped apart by black holes, among other events.

The source of the powerful radiation was discovered to be outside our Milky Way, its location pinpointed by the European Southern Observatory’s Very Large Telescope (VLT).

The European Southern Observatory (ESO) said: "Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe, normally caused by the catastrophic destruction of stars. But no known scenario can completely explain this new GRB, whose true nature remains a mystery."

This GRB is “unlike any other seen in 50 years of GRB observations,” according to Antonio Martin-Carrillo, an astronomer at University College Dublin, Ireland, and co-lead author of a study on this signal recently published in The Astrophysical Journal Letters.

"This is 100 to 1000 times longer than most GRBs,” said Andrew Levan, an astronomer at Radboud University in the Netherlands, and co-lead author of the study.

“More importantly, gamma-ray bursts never repeat since the event that produces them is catastrophic,” said Martin-Carrillo.

Dr. Martin-Carrillo added: “We keep collecting more data. Determining the true distance of this event will be key to measuring its true energy and will help us improve our physical modelling.

"We are still not sure what produced this or if we can ever really find out, but with this research, we have made a huge step forward towards understanding this extremely unusual and exciting object."