In a breakthrough discovery, an international team of astrophysicists from the Netherlands and the UK has unveiled the origin of enigmatic radio pulses lasting seconds to minutes. Unlike traditional emissions from single neutron stars, these long-period transients (LPTs) are caused by two interacting stars, as detailed in a study published in Nature Astronomy.
For years, radio astronomers have been mystified by these periodic signals, which last far longer than the millisecond pulses produced by neutron stars or pulsars. Unlike pulsars, which emit signals every few seconds, LPTs exhibit patterns spanning 10 minutes to several hours, leaving scientists puzzled about their source.
In this groundbreaking research, Dr. Iris de Ruiter (formerly of the University of Amsterdam, now at the University of Sydney) and Dr. Kaustubh Rajwade (University of Oxford) zeroed in on a collection of periodic signals first detected in 2022.
Utilizing the Low-Frequency Array (LOFAR) telescope, the team identified the precise sky location of these signals, tracing them to a star-like object 1,600 light-years away in the constellation Ursa Major.
Follow-up observations using advanced telescopes in the United States revealed that the culprit was not a single star but a cosmic duo—a white dwarf and a red dwarf locked in a tight orbit around a shared center of gravity, completing a full cycle every 125 minutes.
The white dwarf, the dense remnants of a Sun-like star, and its smaller red dwarf companion may produce these radio pulses through one of two mechanisms. The bursts could originate from the powerful magnetic field of the white dwarf itself or be the result of interactions between the magnetic fields of both stars. Further observations are needed to confirm the exact mechanism.
“This discovery shows us that compact objects beyond neutron stars can produce bright radio emissions,” said Dr. Rajwade, who spearheaded the effort to decode the LPTs with the LOFAR telescope. “Each new detection brings us closer to understanding these extreme astrophysical phenomena.”
Dr. de Ruiter added, “Collaborating with experts across various astronomical disciplines allowed us to piece together this puzzle step by step.”
This finding also raises questions about similar systems. About ten comparable radio-emitting systems have been identified in recent years, but their origins—white dwarfs or neutron stars—remain inconclusive.
Dr. Rajwade continues to analyze LOFAR data for additional LPTs. “This is just the beginning. These discoveries redefine our understanding of stellar systems and open new doors to studying how magnetic fields evolve in stars.”
The discovery marks a significant step in unraveling the mysteries of radio astronomy, proving once again that the universe is full of surprises waiting to be uncovered.
Journal Reference:
de Ruiter, I., Rajwade, K.M., Bassa, C.G. et al. Sporadic radio pulses from a white dwarf binary at the orbital period. Nat Astron (2025). DOI: 10.1038/s41550-025-02491-0