In a groundbreaking discovery that challenges our understanding of cosmic phenomena, astronomers using China’s massive FAST radio telescope have uncovered the first definitive evidence that certain fast radio bursts originate from binary star systems rather than isolated celestial objects. This revelation, published in the prestigious journal Science, represents a major leap forward in solving one of astronomy’s most puzzling mysteries.
An international research team led by scientists from the University of Hong Kong, working with China’s Five-hundred-meter Aperture Spherical Telescope (FAST)—affectionately known as “China Sky Eye”—monitored a repeating fast radio burst designated FRB 220529A for nearly 20 months. Their patient observation revealed a distinctive signal pattern indicating the presence of a companion star orbiting the source of these powerful cosmic radio flashes.
The Discovery That Changed Everything
Fast radio bursts are among the universe’s most enigmatic phenomena: millisecond-duration flashes of radio waves so powerful they can be detected from billions of light-years away. While astronomers have detected hundreds of these events since their discovery in 2007, their origin has remained one of astronomy’s greatest unsolved mysteries.
The breakthrough came when researchers detected an unusual phenomenon called an “RM flare”—a sudden, dramatic change in the polarization properties of the radio signal. According to the study published in Science, this change likely resulted from a coronal mass ejection from a companion star contaminating the environment around the fast radio burst source.
Professor Bing Zhang, Chair Professor of Astrophysics at the University of Hong Kong and corresponding author of the paper, explained the significance: the evidence strongly supports a binary system containing a magnetar—a neutron star with an extraordinarily powerful magnetic field—and a star similar to our sun. This represents the first time scientists have definitively linked fast radio bursts to binary stellar systems.
Understanding the Binary Connection
The discovery hinged on observing changes in how radio waves from FRB 220529A travel through space. As these waves pass through magnetized plasma, their polarization angle rotates with frequency—a phenomenon known as Faraday rotation, measured by what scientists call the rotation measure (RM).
Dr. Ye Li of Purple Mountain Observatory and the University of Science and Technology of China, the paper’s first author, described the crucial moment when the team detected an abrupt increase in rotation measure by more than a factor of one hundred. This RM then rapidly declined over two weeks, returning to its previous level—a pattern the team dubbed an “RM flare.”
Such a short-lived change in rotation measure is consistent with dense magnetized plasma briefly crossing the line of sight between Earth and the fast radio burst source. The most natural explanation? A nearby companion star ejected this plasma in an event similar to coronal mass ejections observed from our sun and other stars throughout the Milky Way.
Professor Yuanpei Yang from Yunnan University, a co-first author of the paper, noted that the required plasma characteristics match well with coronal mass ejections launched by solar-type stars, providing strong supporting evidence for the binary system hypothesis.
FAST: The World’s Most Powerful Radio Eye
This discovery showcases the remarkable capabilities of China’s FAST telescope, the largest and most sensitive single-dish radio telescope ever constructed. Nestled in a natural depression in Guizhou Province, FAST’s 500-meter dish—equivalent to 30 football fields—has been systematically monitoring repeating fast radio bursts since 2020 through a dedicated Key Science Program co-led by Professor Zhang.
The telescope’s unparalleled sensitivity proved crucial for this discovery. By November 2024, FAST had discovered over 1,000 pulsars—more than all other telescopes combined during the same period. Its ability to process 38 billion samples per second allows it to detect subtle variations in radio signals that would be invisible to less powerful instruments.
The discovery was confirmed through continuous radio observations using both FAST and Australia’s Parkes telescope. Although the companion star cannot be directly observed at a distance of 2.5 billion light-years, its gravitational and magnetic influence on the fast radio burst source betrayed its presence through the systematic changes in radio wave properties.
Implications for Understanding Magnetars and Fast Radio Bursts
This breakthrough supports a unified physical framework recently proposed by Professor Zhang and his collaborators, suggesting that all fast radio bursts may originate from magnetars. In this model, interactions within binary systems create a preferred geometry that enables more frequent, repeating bursts.
Magnetars are neutron stars possessing magnetic fields trillions of times stronger than Earth’s. These exotic objects are among the most extreme environments in the universe, capable of generating the enormous energies required to produce fast radio bursts. Previous observations had established magnetars as at least one source of these mysterious signals, but the role of binary companions remained unclear until now.
The discovery has profound implications for understanding why some fast radio bursts repeat while others appear only once. According to research published in Nature Communications, binary interactions may be the key factor determining whether a magnetar becomes an active, repeating source of fast radio bursts or produces only occasional single bursts.
Professor Xuefeng Wu of Purple Mountain Observatory, the lead corresponding author, emphasized that this discovery was made possible by persevering observations using the world’s best telescopes and the tireless work of a dedicated research team spanning multiple countries and institutions.
The Road Ahead
While this discovery represents a major breakthrough, it also raises new questions. How common are binary systems among fast radio burst sources? Do all repeating bursts come from binary systems, or do isolated magnetars also produce them? And what specific mechanisms within these binary systems trigger the actual radio bursts?
Continued long-term monitoring of repeating fast radio bursts with facilities like FAST may reveal how prevalent binary systems are among these mysterious sources. The telescope’s open-sky policy, which reserves at least 10 percent of observation time for international astronomers, ensures that researchers worldwide can contribute to unraveling these cosmic mysteries.
As FAST continues its systematic survey of the radio sky, astronomers anticipate discovering additional binary systems hosting fast radio burst sources. Each new detection will help refine our understanding of the physical processes at work in these extreme environments and may ultimately reveal whether binary companions are essential for producing the most active repeating sources.
This research demonstrates the power of patient, systematic observation combined with cutting-edge technology to solve fundamental mysteries about the universe. As our observational capabilities continue to advance, we edge closer to fully understanding the nature and origins of these enigmatic cosmic flashes.
Study Citation: Y. Li et al., “A sudden change and recovery in the magnetic environment around a repeating fast radio burst,” Science (2026). DOI: 10.1126/science.adq3225
