Mysterious Space Signals Went Unexplained for Years – Astronomers Just Found the Star System Behind Them

A puzzling new type of radio signal – lasting seconds to minutes – has been linked to a binary star system featuring a white dwarf and a red dwarf.

Scientists suspect these signals arise from the white dwarf’s intense magnetic field or its interaction with its companion. This discovery suggests that more than just neutron stars can emit powerful radio waves, expanding our understanding of stellar magnetism.

Mysterious Radio Signals from the Milky Way

In recent years, astronomers have been puzzled by a newly discovered cosmic phenomenon – radio pulses from the Milky Way that last from seconds to minutes. These signals are unlike those from known neutron stars, or pulsars, which typically emit bursts in mere milliseconds. Even more unusual, these so-called long-period transients (LPTs) repeat at intervals ranging from tens of minutes to hours, unlike conventional pulsars that pulse every few seconds.

While scientists have proposed several theories to explain these mysterious signals, evidence has been scarce. Now, a breakthrough study led by astronomers from the Netherlands and the UK has provided the first concrete clues about their origin.

Pinpointing the Source: A Star System in Ursa Major

The research focused on a series of these periodic radio signals detected in 2022. Using an advanced imaging technique, a team led by Dr. Iris de Ruiter (then at the University of Amsterdam, now at the University of Sydney) and Dr. Kaustubh Rajwade (University of Oxford) identified multiple LPT pulses in data collected by the Low Frequency Array (LOFAR), an international network of radio telescopes.

Acting like a large radio camera, the telescope could pinpoint the exact location of the radio pulse in the sky that was traced to a star-like object about 1,600 light-years away. Follow-up observations with the 6.5 m diameter 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.

A Dynamic Duo: White Dwarf and Red Dwarf

The two stars, a white dwarf (a rather bright ember of a Sun-like star after it sheds away all the material around it) in orbit around a red dwarf (a star much smaller and lighter than the Sun), orbit a common center of gravity every 125 minutes. The star system is located in the direction of the constellation of the Great Bear (Ursa Major).

According to the researchers, there are two possibilities for how the stars generate the unusually long radio pulses. Potentially, the radio bursts emanate from the strong magnetic field of the white dwarf, or they could be produced by the interaction of the magnetic fields of the white dwarf and its stellar companion. However, further observations are needed to clarify this.

A Breakthrough in Understanding Compact Objects

“Thanks to this discovery, we now know that compact objects other than neutron stars are capable of producing bright radio emission,” comments Dr. Rajwade who leads the effort to find the unexplained LPTs with the LOFAR telescope and helped to identify the periodic pattern between radio pulses.

“We worked with experts from all kinds of astronomical disciplines,” adds Dr. de Ruiter. “With different techniques and observations, we got a little closer to the solution step by step.”

The Search for More LPTs Continues

In recent years, about ten such radio-emitting systems have been discovered by other research groups. However, these groups have not yet been able to prove whether these pulses come from a white dwarf or a neutron star.

Dr. Rajwade continues to search the data from LOFAR for LPTs: “This finding is very exciting! We are starting to find a few of these LPTs in our radio data. Each discovery is telling us something new about the extreme astrophysical objects that can create the radio emission we see. For instance, the unexpected observation of coherent radio emission from the white dwarf in this study could help probe the evolution of magnetic fields in this type of star.”

Explore Further

• Astronomers Just Traced Mysterious Radio Pulses to an Unusual Star Duo
• Astronomers Found a Dead Star Sending Out Mysterious Signals Like a Cosmic Beacon

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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