A PhD student using CSIRO's ASKAP telescope has traced a class of repeating cosmic radio pulses to a white dwarf binary system - the first confirmed source for signals that puzzled radio astronomers for two decades.
Astronomers have identified the source of a class of unexplained repeating cosmic radio signals for the first time, tracing the mysterious pulses to a “cataclysmic variable” - a tight stellar binary in which a dense white dwarf draws material from a companion red dwarf. The finding, published June 1, 2026 in Nature Astronomy, resolves a puzzle that has occupied radio astronomers for nearly two decades.
Long-period radio transients (LPRTs) are coherent, highly polarised bursts of radio emission that repeat at intervals of minutes to hours. They differ fundamentally from ordinary pulsars - rapidly rotating neutron stars whose millisecond-to-second pulses are well understood - because their much longer recurrence intervals did not fit any established model of a compact rotating object. Only about a dozen LPRTs are confirmed, and their physical origin had been debated since the earliest examples were detected in the early 2000s.
Using CSIRO’s ASKAP (Australian Square Kilometre Array Pathfinder) radio telescope in Western Australia, a team led by PhD student Kovi Rose at the University of Sydney identified a new LPRT designated ASKAP J1745-5051. The system emits radio pulses with a period of approximately 1.345 hours. Follow-up observations with X-ray telescopes revealed a matching X-ray signal flickering at the same interval - the first time such a multi-wavelength correspondence had been confirmed for an LPRT.
ASKAP J1745-5051 consists of two stars in an extremely tight mutual orbit. The primary is a white dwarf - roughly Earth-sized but with a mass close to that of the Sun - paired with a smaller red dwarf companion carrying about one-tenth of the Sun’s mass. The two complete a full orbit around their common centre of mass every 1.368 hours.
As the white dwarf’s gravity draws material from the red dwarf, the infalling gas forms a swirling accretion disk. This process generates the powerful, highly polarised radio bursts that ASKAP detects. The near-identical match between the orbital period and the radio pulse period confirmed that the signal is locked to the binary system’s dynamics, not to any freely spinning isolated object.
“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 released by the University of Sydney. “This system gives us a way to decode these signals…acting like a stellar Rosetta stone.”
Previous proposals for the origin of LPRTs centred on isolated compact objects - ultra-long-period pulsars or magnetars spinning far more slowly than typical neutron stars. The ASKAP J1745-5051 data effectively rules that model out for this object, but Rose and colleagues are careful not to over-reach. Not all known LPRTs may share the same origin. The paper’s authors describe the system as “a natural laboratory” for studying matter under extreme magnetic fields, and note that it opens a comparison point for investigating the rest of the class.
Further analysis using ASKAP’s wide-field survey capabilities is expected to find additional white dwarf binary LPRTs, which can then be compared against the examples that remain unexplained.
Unexplained signals that repeat with high regularity have historically attracted attention in anomaly research because periodicity is among the characteristics associated, in theory, with artificial sources. The resolution of ASKAP J1745-5051 adds a confirmed natural mechanism to the catalogue of phenomena capable of producing ordered, repeating signals without any technological origin. The result is a useful reference: it shows what a natural system in this regime looks like, and what its multi-wavelength fingerprint is.
As Rose’s team notes, the discovery does not resolve every LPRT - it resolves one, cleanly, and provides a template for examining the others. For the remaining cases still without a confirmed source, the same systematic approach - multi-telescope, multi-wavelength, cross-matching orbital periods - is now the established method.
The research was conducted in collaboration with CSIRO and international partners and is published in Nature Astronomy (2026).
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