Mysterious radio bursts have been traced to the edge of an ancient, dying galaxy

In February 2024, scientists on Earth detected a powerful radio burst from outer space. Seeking to discover its source, they trace the brief flash of energy to its extraterrestrial origin, and discover something unexpected.

Scientists led by Northwestern University and McGill University have tracked a fast radio burst (FRB) to the edges of an ancient elliptical galaxy. Scientists previously thought that these fast radio bursts, which generate more energy in a single flare than our Sun generates in an entire year, are produced exclusively by young galaxies that are steadily producing new stars. But the latest investigations are detailed in two parts sister studies Posted on January 21 Astrophysical Journal Letters, They prompt astronomers to reconsider the possible diversity of FRB sources.

Dubbed FRB 20240209A, in February 2024, the FRB was not just a one-off operation. Between February and July 2024, the same source ignited 21 times.

“The prevailing theory is that fast radio bursts come from magnetars that were formed by collapsing supernovae,” said Tarana Eftekhari of Northwestern University, who participated in both studies, at one of the universities. statement. Magnetars are neutron stars with very strong magnetic fields. Neutron stars are very small, dense celestial bodies that are thought to form following the explosive death of some large stars, i.e. supernovas.

“That doesn’t seem to be the case here,” Eftekhari continued. “Although massive young stars end their lives as supernovae collapsing at their core, we see no evidence of young stars in this galaxy. Thanks to this new discovery, a picture emerges showing that not all fast radio bursts come from young stars. Perhaps There is a subset of fast radio bursts associated with legacy systems.

The ancient galaxy in question is 11.3 billion years old and 2 billion light-years away. Using computer simulations, Eftekhari and her colleagues discovered that the galaxy is extremely bright, and 100 billion times more massive than our Sun.

“It appears to be the largest galaxy hosting fast radio bursts to date,” Eftekhari said. “They are among the most massive galaxies out there.” The unusual fast radio bursts not only originated from an ancient galaxy, but also from the edge of that galaxy, precisely 130,000 light-years from its center.

“Among fast burst clusters, these fast bursts are located ‘farthest’ from the center of their host galaxy,” said McGill’s Vishwanji Shah, who was involved in both studies. “This is both surprising and exciting, as fast radio bursts are expected to originate within galaxies, often in star-forming regions. The location of this fast radio burst so far outside its host galaxy raises questions about how such energetic events can occur in regions where New stars are formed in it.

But FRB 20240209A is not the first FRB discovered far from active star formation regions, but rather the second. In 2022, astronomers traced M81 FRB, located 12 million light-years from Earth, to a cluster of stars on the edge of the galaxy Messier 81.

FRB 20240209A “could be a twin of event M81 (M81 FRB). It is far from its parent galaxy (far from where any stars are born), and the number of stars in its parent galaxy is very old. “It was in its heyday, and now it’s about to retire,” said Wen-Fei Fong of Northwestern University, who participated in both studies. “At the same time, this kind of ancient environment is making us rethink our standard models of FRB flows and turn to more exotic channel formations, which is exciting.”

One study suggests that, like the M81 FRB, the new fast bursts may also have originated from a cluster of stars, called a globular cluster.

“A globular cluster origin for these recurring fast radio bursts is the most likely scenario to explain why these fast radio bursts exist outside their host galaxy,” Shah explained. “We do not know for sure whether a globular cluster exists at the location of the FRB and we have made a proposal to use the James Webb Space Telescope to continue observations of the location of the FRB. If yes, this would make this fast radio burst the second FRB known to exist at Globular cluster If this is not the case, we will have to consider alternative exotic scenarios for the origin of fast radio bursts.

In other words: back to the drawing board!