A fast radio burst from a dead galaxy puzzles astronomers

A staccato blast of electromagnetic energy has been tracked to an old, dead galaxy for the first time. The discovery supports the idea that there are more ways to produce such flares, called fast radio bursts, than originally thought.

Fast radio bursts, or FRBs, are millisecond-long eruptions of intense radio waves. Astronomers have observed thousands of these blasts, but only about 100 have been traced back to their origins, says astronomer Tarraneh Eftekhari of Northwestern University in Evanston, Ill. Almost all of them came from lively neighborhoods full of young stars.

From February to July 2024, the CHIME radio telescope array in Canada detected 22 bursts from an FRB dubbed FRB 20240209A. Six of those bursts were also detected nearly 70 kilometers away at a CHIME auxiliary telescope called k’niʔatn k’l◡stk’masqt, which means “a listening device for outer space” in the language of the Upper Similkameen people.

Combining those signals let Eftekhari and colleagues triangulate the FRB’s location in the sky. Surprisingly, it came from the outskirts of an ancient galaxy, about 11 billion years old, whose star-forming years are long behind it, the team reported in two papers in the Feb. 1 Astrophysical Journal Letters.

Astronomers think FRBs come mostly from magnetized stellar corpses called magnetars, which are remnants of supernova explosions. Such supernovas are expected where a lot of stars are actively forming — not in an old galaxy, and certainly not so far from the galaxy’s center.

“The host galaxy itself is a dead galaxy,” says coauthor Vishwangi Shah, an astronomer at McGill University in Montreal. “So the question is: How are such energetic signals being produced from such a region of space?”

Another odd FRB could offer a clue. In 2021, astronomers found an FRB emanating from a globular cluster, a tight ball of mostly old stars in a relatively nearby galaxy. That blast inspired astronomers to think about how old or dead stars could form magnetars. Perhaps magnetars come from white dwarfs collapsing under their own gravity, for example, or out of the wreckage of two neutron stars colliding.

The team has applied for observations with the James Webb Space Telescope to see if there is a globular cluster in the spot the new FRB came from.

“I think that magnetars are still a compelling origin story for FRBs,” Eftekhari says. “But I think what this discovery is telling us is there are probably multiple ways you can form magnetars that produce FRBs.”