Scientists Find Cosmic ‘Rosetta Stone’ That Could Finally Decode Mysterious Deep-Space Radio Signals

University of Sydney PhD Student Solves One of Astronomy’s Strangest Puzzles With Discovery of Rare Two-Star System

For years, astronomers have been picking up strange, repeating bursts of radio energy from deep in the galaxy. Only about a dozen have been detected so far, and the origins of ten of them are still unknown. Now, a PhD student and his team may have cracked the code.

Kovi Rose, a doctoral researcher at the University of Sydney, led an international team that discovered what researchers are calling a “Rosetta stone” for these mysterious signals. Just as the original Rosetta Stone unlocked the meaning of ancient Egyptian hieroglyphics, this newly identified star system may finally give astronomers a key for interpreting one of the stranger unsolved problems in modern astronomy.

“For the first time we have pinpointed the origin of these signals, confirming the source to be a ‘cataclysmic variable’, or an accreting white dwarf star,” Rose said in a statement.

The system, published in Nature Astronomy, consists of a dense, burned-out stellar remnant, a white dwarf, actively shredding material from a companion red dwarf star. As that stolen material spirals inward, it triggers powerful bursts of radio waves and X-rays that repeat on a roughly 1.3-hour cycle tied directly to the two stars’ orbital motion.

What Are These Mysterious Deep-Space Radio Signals?

Radio telescopes have been detecting this class of signals in recent decades, with astronomers calling them long-period radio transients. They are bright, brief bursts of radio energy that repeat with clockwork regularity, anywhere from every few minutes to every few hours.

“Long-period radio transients have puzzled astronomers for years,” Rose said. “We’ve only found about a dozen, and their origins have been unclear. Now, we’ve been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star.”

Two leading explanations had been proposed. One suggested the bursts originate from slowly rotating magnetars, a type of collapsed star with extremely strong magnetic fields. The other pointed to binary star systems where a white dwarf siphons material off a companion. White dwarfs are the dense, cooling remnants left behind when stars like our Sun exhaust their fuel, roughly the size of Earth but carrying the mass of the Sun.

Until now, while a handful of recent observations had pointed toward the white dwarf explanation, the mechanism actually generating bursts at this power level remained unclear. This is the first case where, as Professor Tara Murphy, Head of School at the University of Sydney’s School of Physics, put it, researchers “can clearly see both stars and the accretion process in action.”

How Astronomers Found and Confirmed the White Dwarf Radio Transient

Researchers identified the system, catalogued as ASKAP J174508.9-505149, using the Australian SKA Pathfinder radio telescope array in Western Australia. The team was scanning a large survey for sources with a specific kind of circular radio polarization, essentially radio waves that spin in a particular direction. Out of roughly three million sources, only about 100 showed that signature, and this object was the only one among them without a known astronomical identification.

After pinpointing the location with the MeerKAT radio telescope in South Africa, researchers cross-referenced it against optical databases, turning up an extremely faint optical source in a catalog maintained by the European Space Agency.

Confirmation came from two telescopes in Chile, the SOAR telescope and the Magellan telescope at Las Campanas Observatory, which split the object’s light into its component colors. That analysis revealed characteristic emission from hydrogen and helium, the hallmark of a magnetized white dwarf actively pulling material from a smaller, cooler red dwarf companion.

By measuring the slight Doppler shifts in those emissions, the same effect that makes an ambulance siren sound higher as it approaches and lower as it passes, the team pinned the orbital period at approximately 1.368 hours. That makes this the shortest-period object of its class ever found, sitting right at the theoretical lower limit for how tight a binary orbit of this type can get before the two stars begin to drift apart.

Radio Bursts, X-Rays, and a Signal Pattern Found Nowhere Else in the Known Universe

Radio observations spanning nearly two years, gathered from multiple telescopes, confirmed that the bursts repeat on the same 1.3-hour schedule as the orbital period. Their output exceeds 100 times the radio power of any previously known feeding white dwarf binary, outshining roughly 99 percent of all radio-emitting stars. That level of energy rules out ordinary stellar magnetic activity as an explanation.

“These emissions are all tied to the orbital motion of the system,” Rose said. “But interestingly, the radio and X-ray signals don’t peak at the same time, which tells us they’re being produced in different regions of the system.”

Writing in The Conversation, Rose explained what he believes is driving the powerful radio bursts: both stars carry magnetic fields typically thousands of times stronger than an MRI machine, with charged particles streaming from the red dwarf toward the white dwarf. That combination of extreme magnetic fields and a constant flow of energized material appears to be the key ingredient.

One feature caught researchers especially off guard: a fine-scale pattern in the brightness of the radio bursts, with peaks spaced closely in frequency that shift and drift over time. Astronomers had detected this exact pattern in only one other place in the known universe, in the interaction between Jupiter and its volcanic moon Io. In that case, the pattern forms when radio beams pass through energized gas near Io, creating an interference effect similar to the rainbow shimmer seen on a soap bubble. Researchers propose that gas built up through the white dwarf’s feeding process is producing the same effect here. The radio bursts also switch off entirely for several hours at a stretch, tending to arrive near the moments when the two stars are aligned from Earth’s perspective.

Using two space-based X-ray telescopes, the Neil Gehrels Swift Observatory and the Einstein Probe, the team detected X-rays from the system whose brightness swung by a factor of more than ten across different observations, varying on the same 1.3-hour orbital schedule. That pattern is consistent with material being funneled unevenly onto the white dwarf by strong magnetic fields. Only two other objects in this class had ever been detected in X-rays before this one.

A Past Explosion and What Comes Next for White Dwarf Research

Beyond the radio and X-ray activity, the system carries hints of something more dramatic in its past. Certain properties suggest the white dwarf may be slightly out of step with its orbital rhythm, possibly the fingerprint of a past nova, a brief thermonuclear explosion on the white dwarf’s surface after accumulating too much stolen material. Rose and colleagues note that a geometric model using realistic magnetic field strengths can reproduce many of the observed radio features, including the signal’s intermittency and the frequency drift pattern.

Rose describes the system as a potential reference point for understanding others like it. “This system gives us a way to decode these signals. It could help us determine whether other long-period transients are more like pulsars or like white dwarf systems, acting like a stellar Rosetta Stone,” he said. Whether white dwarf binaries can account for the full population of these mysterious signals remains an open question, one researchers say will require new discoveries, detailed simulations, and coordinated follow-up. But with a confirmed system now on the books, backed by spectroscopic evidence, X-ray data, and nearly two years of radio observations all pointing to the same source, astronomers have, for the first time, a concrete case to build from.