In February 2024, scientists on Earth detected a powerful radio burst from space. Desperate to discover where it came from, they trace the brief flash of energy back to its extraterrestrial source—and discover something unexpected.

Scientists led by Northwestern University and McGill University have tracked fast radio scattering (FRB) at the edges of an ancient elliptical galaxy. Scientists used to think that these fast radio bursts, which produce more energy in a single flare than our Sun produces in an entire year, were produced exclusively by young galaxies that were constantly churning out new ones. star Recent investigations, however, have detailed both sister study published on January 21 at The Astrophysical Journal Letters, prompting astronomers to reconsider the potential diversity of FRB sources.

Called FRB 20240209A, the February 2024 FRB is not a one-and-done. Between February and July 2024, the same source flashed 21 times.

“The prevailing theory is that FRBs come from magnetars formed by core-collapse supernovae,” Tarraneh Eftekhari of Northwestern University, who participated in both studies, said in a university statement. Magnetars are neutron stars with very strong magnetic fields—and neutron stars are extremely small and dense objects in the sky that are thought to form after the death of a few massive stars, namely, supernovae.

“That doesn’t appear to be the case here,” Eftekhari continued. “While young, massive stars end their lives as core-collapse supernovae, we don’t see any evidence of young stars in this galaxy. Thanks to the new discovery, a picture has emerged that shows that not all FRBs come from young stars. There is probably a subpopulation of FRBs associated with old systems. “

The ancient galaxy in question is 11.3 billion years old, and 2 billion lightyears away from us. Using computer simulations, Eftekhari and his colleagues discovered that the galaxy is incredibly bright, and 100 billion times larger than our Sun.

“This appears to be the largest FRB host galaxy to date,” Eftekhari said. “It’s one of some of the biggest galaxies out there.” Not only does the unusual FRB come from an old galaxy, it also comes from the galaxy’s edge—specifically, 130,000 lightyears from its center.

“Among the FRB population, this FRB is located (farthest) from the center of its host galaxy,” said McGill’s Vishwangi Shah, who participated in both studies. “This is surprising and exciting, because FRBs are expected to originate inside galaxies, usually in star-forming regions. The location of this FRB so far outside its host galaxy raises questions about how such that energetic events occur in regions where no new stars are forming.

But FRB 20240209A isn’t the first FRB detected far from regions of active star formation—it’s the second. In 2022, astronomers tracked the M81 FRB, located 12 million light years from Earth, to a cluster of stars on the edge of the Messier 81 galaxy.

FRB 20240209A “will be the twin of the M81 event (M81 FRB). It is far from its home galaxy (far from where any stars are born), and the stellar population of its home galaxy is very old. It’s had its hey-day and is now coasting into retirement,” said Wen-fai Fong of Northwestern University, who participated in both studies. “At the same time, this kind of ancient environment makes us rethink our conventional models of FRB progenitors and return to very different channels of formation, which is exciting.”

One of the studies suggests that, like the M81 FRB, the new FRB may also originate from a group of stars, called a globular cluster.

“A globular cluster origin for this recurring FRB is the most likely scenario to explain why this FRB is located outside the host galaxy,” Shah explained. “We do not know if there is a globular cluster in the FRB’s position and have submitted a proposal to use the James Webb Space Telescope for follow-up observations of the FRB’s location. If so, it will make this FRB is only the second FRB known to reside in a globular cluster.Otherwise, we have to consider alternative exotic scenarios for the FRB’s origin.

In other words: back to the drawing board!