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In February 2024, Earth scientists detected a powerful radio burst from space. Trying to discover where it was coming from, they followed the brief burst of energy back to its terrestrial source and discovered something unexpected.
Scientists led by Northwestern University and McGill University observed a fast radio burst (FRB) at the edges of an ancient elliptical galaxy. Scientists previously thought that these rapid radio bursts, which produce more energy in a single flare than our Sun produces in an entire year, are produced only by young galaxies that are continually blowing out new stars. However, recent studies are detailed in two parts sister is studying Published on January 21 Astrophysical Journal Letters, prompting astronomers to reconsider the potential diversity of FRB sources.
Dubbed FRB 20240209A, the February 2024 FRB wasn’t just a fluke. Between February and July 2024, the same source flared 21 times.
“The common theory is that FRBs are formed from magnetars created by the collapse of the core,” Northwestern University’s Tarraneh Eftekhari, who participated in both studies, said in a statement. statement. Magnetars are neutron stars with very strong magnetic fields, and neutron stars are extremely small and dense celestial bodies thought to have formed as a result of the explosive deaths of some large stars, known as supernovae.
“It doesn’t seem that way here,” continued Eftekhari. “Although young, massive stars end their lives as core-collapse supernovae, we see no evidence of young stars in this galaxy. This new discovery paints a picture that shows that not all FRBs are from young stars. Perhaps there is a subpopulation of FRBs associated with older systems.
The old galaxy in question is 11.3 billion years old and 2 billion light years away. Using computer simulations, Eftekhari and colleagues discovered that the galaxy is extremely bright and 100 billion times larger than our Sun.
“It appears to be the most massive FRB galaxy to date,” Eftekhari said. “It’s one of the biggest galaxies out there.” The unusual FRB was located not only from an old galaxy, but also from the edge, or rather the center, 130,000 light-years away.
“Among the FRB population, this FRB is (farthest) from the center of its galaxy,” said Vishwangi Shah of McGill, who participated in both studies. “This is both surprising and exciting because FRBs are expected to occur inside galaxies, often in star-forming regions. “The fact that this FRB is so far outside its own galaxy raises questions about how such energetic events can occur in regions where no new stars are forming.”
But FRB 20240209A is not the first FRB to be detected far from active star-forming regions, but the second. In 2022, astronomers tracked the M81 FRB, 12 million light-years away from Earth, to the star cluster outside the galaxy Messier 81.
FRB 20240209A “may be the twin of Event M81 (M81 FRB). It is far from its own galaxy (far from where any stars are born), and the stellar population in its own galaxy is quite old. said Wen-fai Fong of Northwestern University, who participated in both studies. “At the same time, this type of old environment is forcing us to reconsider our standard FRB progenitor models and to consider more exotic formation channels, which is exciting.”
One study suggests that, like the M81 FRB, the new FRB may originate from a cluster of stars called a globular cluster.
“A global cluster origin for this recurrent FRB is the most likely scenario to explain why this FRB is located outside the host galaxy,” explained Shah. “We do not know for sure whether there is a globular cluster at the FRB’s position, and we have proposed using the James Webb Space Telescope to track the FRB’s location. If so, this would make this FRB the second FRB known to be located in a globular cluster. Otherwise, we would have to consider alternative exotic scenarios for the origin of the FRB.”
In other words: back to the drawing board!
