Astronomers have finally traced mysterious radio pulses in the Milky Way to a unique cosmic duo—a red dwarf and a white dwarf orbiting each other every two hours.
This discovery challenges previous assumptions that only neutron stars produce such signals.
Mysterious Radio Pulses in Space
An international team of astronomers, led by Dr. Iris de Ruiter from the University of Sydney, has discovered that a white dwarf and a red dwarf orbiting each other every two hours are emitting radio pulses.
By using optical and x-ray telescopes for follow-up observations, the researchers were able to pinpoint the exact source of these pulses. This marks the first time astronomers have confirmed the origin of such radio emissions, which have been detected throughout the Milky Way.
Their findings have been published today (March 12) in Nature Astronomy.
Unraveling the Cosmic Mystery
In recent years, advances in data analysis have allowed scientists to detect radio pulses lasting from seconds to minutes, seemingly originating from stars within our galaxy. While there have been many theories about what causes these bursts, no definitive proof existed until now. This study, conducted by Dr. de Ruiter during her time at the University of Amsterdam, provides the long-awaited answer.
Dr. de Ruiter, who received her doctorate from the University of Amsterdam in October 2024, is now a postdoctoral researcher at the University of Sydney. During the last year of her PhD, she developed a method to search for radio pulses of seconds to minutes in the historical archive of LOFAR, the Low-Frequency Array telescope in the Netherlands.
While improving the method, Dr. de Ruiter discovered a single pulse in the 2015 observations. When she subsequently sifted through more archive data from the same patch of sky, she discovered six more pulses. All the pulses came from a source called ILTJ1101.
The Red and White Dwarf Duo
Follow-up observations with the 6.5m Multiple Mirror Telescope in Arizona and the Hobby-Eberly Telescope in Texas (USA) showed that it is not one flashing star, but two stars that together cause the pulse. The two stars, a red dwarf and a white dwarf, orbit a common center of gravity every 125 minutes. They are located about 1600 light-years from us in the direction of the Big Dipper, also known as the Plough, within the Ursa Major constellation.
Astronomers believe that the radio emission is caused by the interaction of the red dwarf with the white dwarf’s magnetic field.
Astronomers plan to study the ultraviolet emission of these entwined stars in detail. This will help to determine the temperature of the white dwarf and learn more about the history of white and red dwarfs.
“It was especially cool to add new pieces to the puzzle,” Dr. de Ruiter said. “We worked with experts from all kinds of astronomical disciplines. With different techniques and observations, we got a little closer to the solution step by step.”
Neutron Stars No Longer Alone
Because of this discovery, astronomers now know that neutron stars do not have the monopoly on bright radio pulses. In recent years, other research groups have discovered about 10 such radio-emitting systems. However, these groups have not yet been able to prove whether these pulses come from a white dwarf or a neutron star.
Researchers are now searching through the LOFAR data to find more such long-period pulses. Co-author Dr. Kaustubh Rajwade (University of Oxford, UK) said: “There are probably many more of these types of radio pulses hidden in the LOFAR archive, and each discovery teaches us something new.”
Reference: “Sporadic radio pulses from a white dwarf binary at the orbital period” by I. de Ruiter, K. M. Rajwade, C. G. Bassa, A. Rowlinson, R. A. M. J. Wijers, C. D. Kilpatrick, G. Stefansson, J. R. Callingham, J. W. T. Hessels, T. E. Clarke, W. Peters, R. A. D. Wijnands, T. W. Shimwell, S. ter Veen, V. Morello, G. R. Zeimann and S. Mahadevan, 12 March 2025, Nature Astronomy.
DOI: 10.1038/s41550-025-02491-0
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