Scientists Find a ‘Rosetta Stone’ in Space That Could Explain Mysterious Radio Signals

Astronomers have identified a rare stellar system that could help explain a puzzling class of repeating radio signals from deep space. The object, known as ASKAP J1745-5051, is a pair of stars consisting of a highly magnetic white dwarf and a low-mass companion, and it produces repeating radio bursts and X-rays roughly every 1.4 hours. The findings were published in Nature Astronomy.

The discovery is important because astronomers have detected only a small number of these signals, known as long-period radio transients (LPTs), and have struggled to determine what produces them. ASKAP J1745-5051 provides strong evidence that at least some LPTs come from binary systems containing white dwarfs. That makes the system a possible “Rosetta stone” for interpreting other unexplained signals in the Milky Way.

A strange signal leads astronomers to a stellar pair

The object was first discovered during an untargeted search for highly circularly polarized radio sources using the Australian SKA Pathfinder (ASKAP) radio telescope. Follow-up observations with the MeerKAT radio telescope helped refine its position, while optical observations identified a possible counterpart.

Scientists then used optical spectroscopy from the Southern Astrophysical Research Telescope and the Magellan telescopes to study the system. The observations showed strong hydrogen and helium emission lines, features associated with magnetic cataclysmic variables, a type of binary system in which a strongly magnetized white dwarf pulls material from a companion star.

The two stars orbit each other extremely quickly. Researchers measured an orbital period of about 1.37 hours, while the radio pulses repeat on a closely matching timescale. This close match showed that the radio activity is connected to the motion of the binary system.

The system also produces X-rays that vary with the same orbital cycle. Observations from NASA’s Neil Gehrels Swift Observatory and the Einstein Probe X-ray Telescope detected X-ray activity associated with the system, providing additional evidence that material is being transferred onto the white dwarf.

Why the white dwarf matters

A white dwarf is the dense remnant left behind after a star like the Sun reaches the end of its normal life. In this system, the white dwarf is strongly magnetized and is interacting with a much smaller companion, likely an M-type dwarf.

The white dwarf’s gravity pulls material from its companion. That material forms a highly energetic environment around the white dwarf and can produce X-rays. At the same time, the magnetic fields surrounding the two stars interact with charged particles, creating conditions that can generate powerful, highly polarized radio emission.

The radio pulses are unusual in several ways. They are highly polarized, can change their frequency, and can disappear for several hours before returning. Researchers also detected narrow structures within the radio pulses, suggesting that the emission is passing through a complex plasma environment around the binary.

Lead author Kovi Rose, an astronomer at the University of Sydney, said the discovery strengthens the connection between LPTs and white dwarf binaries. As reported by ScienceAlert and ScienceDaily, Rose described the system as a potential “stellar Rosetta stone” because it could help researchers determine whether other mysterious long-period radio transients come from similar systems.

A possible explanation for other cosmic signals

Long-period radio transients are relatively new to astronomy. Their radio bursts repeat over periods ranging from minutes to hours, but their physical origins have remained uncertain. Scientists had considered several possibilities, including slowly rotating magnetars and white dwarf systems with companion stars.

ASKAP J1745-5051 does not prove that every LPT comes from a white dwarf binary. Instead, the observations show that accreting cataclysmic variables make up at least part of the LPT population. The researchers say determining whether the same process explains the entire class will require more observations, detailed modeling and the discovery of additional LPTs.

Professor Tara Murphy of the University of Sydney and the ARC Center of Excellence for Gravitational Wave Discovery said the system is especially valuable because scientists can observe both stars and the accretion process directly, helping connect features that had previously appeared separately in other LPTs.

The researchers plan to continue observing ASKAP J1745-5051 with radio, optical and X-ray telescopes. Combining these observations could reveal more about how the binary’s magnetic fields and flowing material produce the repeating bursts.

For now, ASKAP J1745-5051 gives astronomers a clearer physical example of what may be behind at least some of the strange radio signals appearing across the Milky Way. The discovery does not solve the entire LPT mystery, but it gives scientists a concrete system against which other unexplained signals can be compared.