The location of the fast radio burst, indicated by the oval outlines, is on the outskirts of a massive elliptical galaxy, the yellow oval at right. (Credit: Gemini Observatory)
In a nutshell
- Astronomers have discovered repeated radio burst signals coming from an unprecedented location – 40,000 light-years away from the center of an ancient, inactive galaxy located 2 billion light-years from Earth.
- The discovery challenges existing theories about these mysterious signals, since they were found far from any star-forming regions where scientists typically expect to find their source.
- The leading explanation is that the signals may be coming from a dense cluster of old stars called a globular cluster orbiting the galaxy — only the second time such signals have been linked to this type of stellar environment.
MONTREAL — Astronomers have made a perplexing discovery that’s pushing the boundaries of what we know about mysterious cosmic signals. Using specialized telescopes, they’ve detected powerful radio bursts coming from an unexpected location: the distant outskirts of an ancient, inactive galaxy located 2 billion light-years from Earth.
The discovery began when researchers using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope detected repeated bursts of intense radio waves from a source in the northern constellation Ursa Minor. These cosmic signals, known as fast radio bursts (FRBs), appear as powerful flashes that last for just milliseconds.
Between February and July 2024, the team observed 22 separate bursts from this single source, dubbed “FRB 20240209A.” To precisely locate these signals, they combined observations from CHIME with those from a partner facility called KKO, located 66 kilometers away. This combination worked like a giant pair of astronomical binoculars, allowing unprecedented precision in pinpointing the bursts’ origin.
What they found challenged existing theories: the signals were coming from approximately 40,000 light-years away from the center of their host galaxy –roughly twice the distance from Earth to the center of our Milky Way. This represents the largest offset from a host galaxy ever observed for an FRB source.
Even more puzzling was the nature of the host galaxy itself. Unlike most galaxies where these signals have been found before, this one is an elliptical galaxy estimated to be 11.3 billion years old, which is quite ancient by cosmic standards. With a mass more than 100 billion times that of our Sun, this galaxy is effectively “dead,” meaning new stars rarely form there.
“This is not only the first FRB to be found outside a dead galaxy, but compared to all other FRBs, it’s also the farthest from the galaxy it’s associated with,” said Vishwangi Shah, a doctoral student at McGill University and lead author of the study, in a statement. “The FRB’s location is surprising and raises questions about how such energetic events can occur in regions where no new stars are forming.”
The discovery, described in The Astrophysical Journal Letters, challenges the leading theory that these bursts come from magnetars, which are highly magnetized, spinning neutron stars left over from the explosive deaths of massive young stars. In an galaxy as old as this one, such stellar remnants should have disappeared long ago.
One possible explanation is that the bursts might be coming from a globular cluster — a dense collection of ancient stars that orbits the main galaxy. “The source could be in a globular cluster, a dense region of old, dead stars outside the galaxy. If confirmed, it would make FRB 20240209A only the second FRB linked to a globular cluster,” Shah noted.
To investigate further, the research team used the Gemini North telescope in Hawaii to study this region in detail. While they were looking for signs of a small companion galaxy that might be hosting these bursts, they found nothing visible at that location, deepening the mystery.
The timing pattern of these signals provides additional intrigue. After its initial discovery in February 2024, the source remained relatively quiet for several months before dramatically increasing its activity in June, producing 17 bursts in just one month.
It’s been an exciting time for fast radio burst research. A third telescope array is being added to the CHIME network at Hat Creek Observatory in Northern California, which will help scientists locate these mysterious bursts with even greater precision. “When paired with the three outriggers, we should be able to accurately pinpoint one FRB a day to its galaxy, which is substantial,” said Calvin Leung, a Miller Postdoctoral Fellow at UC Berkeley and co-author of the study.
This discovery expands our understanding of where these enigmatic signals can occur and what might be producing them. Finding repeating bursts in such an unexpected location suggests multiple formation pathways for these cosmic phenomena, providing new directions for future research.
Paper Summary
Methodology
The research team used a combination of radio telescope observations and optical imaging to study this FRB source. The initial detections were made using CHIME, a unique telescope in British Columbia that continuously scans the northern sky for radio signals. To precisely locate the source, they used interferometry – a technique that combines signals from multiple telescopes (in this case, CHIME and KKO) to achieve much higher precision than either telescope could achieve alone. They then used the Gemini North telescope in Hawaii to capture detailed images of the region where the FRB was located.
Results
The study identified 22 separate bursts over a six-month period, with varying intensities and characteristics. The source showed a distinct period of heightened activity in June 2024, producing 17 bursts in one month. The bursts were located 40,000 light-years from the center of a massive elliptical galaxy, making it the most distant FRB from its host galaxy ever observed. The host galaxy itself is unusually large and old for an FRB source.
Limitations
The research was limited by the sensitivity and frequency range of the CHIME telescope, meaning some weaker bursts might have gone undetected. Additionally, the team’s ability to study potential host environments was constrained by the sensitivity limits of current optical telescopes, leaving open the possibility of undetected very faint companion galaxies.
Discussion and Takeaways
The study demonstrates that FRBs can occur in environments very different from where they were previously found, suggesting multiple possible formation channels. The finding challenges existing theories about FRB origins and adds new complexity to our understanding of these mysterious phenomena. The research also showcases the effectiveness of new astronomical techniques for precisely locating these elusive sources.
Funding and Disclosures
The research was supported by numerous institutions and funding sources, including the Gordon & Betty Moore Foundation, the National Science Foundation, and various Canadian research organizations. The observations used multiple telescopes including CHIME, KKO, and the Gemini North telescope.
Publication Information
Published in The Astrophysical Journal Letters, Volume 979, L21 (14pp), February 1, 2025. Authors include Vishwangi Shah as lead author, along with 61 co-authors from various institutions worldwide.
