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Rare star system identified in the Milky Way offers a new key to investigate radio signals that repeat at unusual intervals, bringing astronomers closer to the origin of phenomena that challenge traditional models on compact stars, magnetism, and energetic emissions in deep space.
An international team led by the University of Sydney identified the star system ASKAP J1745−5051 as a possible source of the so-called long-period radio transients, cosmic signals that appear at intervals longer than those predicted for traditional sources.
The discovery was led by PhD student Kovi Rose, in partnership with researchers linked to CSIRO, and published on June 1, 2026, in the scientific journal Nature Astronomy.
The system comprises a white dwarf, an extremely dense stellar remnant with a size close to that of Earth, and a low-mass companion, described by researchers as a red dwarf or a similar star.
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The two stars complete an orbit in just over an hour, a period compatible with the emission cycles observed in radio and X-rays by the instruments used in the investigation.
The research is noteworthy for linking the detected signal to an identified physical source, rather than just an isolated emission recorded in a distant region of the Milky Way.
From the observations, scientists associated the emissions with a binary system in the process of accretion, in which the white dwarf draws material from its companion star.
According to the University of Sydney, the pulses repeat in a cycle of about 1.4 hours, equivalent to approximately 84 minutes.
In the scientific article, the authors estimate the orbital period at 1.368 ± 0.053 hours, a value used to support the interpretation that the regularity of the signals is related to the movement of the two stars.
Rare radio signal intrigued astronomers
Long-period radio transients form a still recent class of astronomical phenomena, characterized by bursts that repeat at intervals of tens of minutes or more than an hour.
This behavior does not easily fit into the models used to explain conventional pulsars and other compact sources already known to astronomy.
Among the hypotheses evaluated in recent years was the possibility that these signals were produced by neutron stars with extremely slow rotation.
However, according to the researchers involved in the study, physical models indicate that objects of this type, when rotating so slowly, would hardly generate emissions with the characteristics observed in some of these events.
With the identification of ASKAP J1745−5051, the hypothesis gained strength that at least a portion of these signals may originate in binary systems with magnetic white dwarfs.
The research does not conclude the debate on all long-period radio transients but presents an observed case that can be compared to other sources still without a definitive explanation.
In a statement from the University of Sydney, Kovi Rose stated that the researchers managed to indicate the origin of these signals and confirm the source as a cataclysmic variable, that is, a system with an accreting white dwarf.
This attribution relates the astronomical observation to a known physical mechanism, allowing the same interpretation to be tested in other similar objects detected in the galaxy.
White dwarf helps explain radio and X-ray emission
In the ASKAP J1745−5051 system, the white dwarf attracts material from the companion star, a process that alters the environment around the compact object and creates conditions for emissions in different ranges of the electromagnetic spectrum.
When this gas approaches the white dwarf, it heats up and begins to emit X-rays, a signature associated with accretion environments with high temperatures.
At the same time, the interaction between the magnetic fields of the two stars and the plasma present in the system is pointed out by the authors as one of the explanations for the regular radio emissions.
The observations indicate that the radio and X-ray signals do not peak at exactly the same time, suggesting an origin in different regions of the binary system.
This interval between emissions helps researchers separate the physical processes involved, without treating radio and X-rays as manifestations necessarily produced at the same point.
According to the interpretation presented in the study, the X-rays are associated with the heating of the material attracted by the white dwarf, while the radio waves arise in regions of magnetic interaction and charged particles.
Another point highlighted by Nature Astronomy is the radio luminosity of ASKAP J1745−5051, considered unusual when compared to other observed cataclysmic variables.
According to the article, ASKAP J1745−5051 is about 100 times brighter in radio than comparable cataclysmic variables, even when the authors consider the lower limit of the estimated distance.
Cosmic Rosetta Stone may guide new studies
The expression “Rosetta Stone” was used by researchers linked to the study because the system can serve as a reference to interpret other radio signals with similar behavior.
The comparison is based on the idea that ASKAP J1745−5051 provides a case observed in multiple wavelengths, with an identified source and proposed physical mechanism.
Rose stated that the system can help determine if other long-period transients resemble more closely pulsars or white dwarf systems.
This distinction is relevant to research because different objects require different physical explanations to produce regular and energetic signals over such long time scales.
The authors do not claim that all long-period radio transients have the same origin.
The research itself indicates that cataclysmic variables in accretion may comprise at least part of this population, keeping open the possibility of other mechanisms acting on different sources.
The system also allows the study of plasma and magnetism under extreme conditions, according to the University of Sydney, in an environment that cannot be reproduced with the same parameters in a laboratory.
For astrophysics, such observations help test models about compact objects, mass transfer, and radiation emission in high-energy binary systems.
ASKAP Radio Telescope was used in identification
The signals were detected with the Australian SKA Pathfinder, a radio telescope known as ASKAP and operated by CSIRO, Australia’s national science agency.
The instrument has wide sky coverage and was developed to observe radio sources, including variable objects and phenomena that may appear for short periods or in regular cycles.
The investigation also gathered data obtained in other ranges of the electromagnetic spectrum, such as X-rays and visible light, to analyze the system’s dynamics with more than one type of observation.
This combination of information allowed researchers to identify the stellar pair and relate the radio signal to the accretion process described in the article.
Without the data in multiple wavelengths, the source could continue to be classified only as a periodic emission of undefined origin in the Milky Way.
Nature Astronomy also records observations made with instruments like the Einstein Probe and the Swift observatory, used to investigate emissions in X-rays and ultraviolet.
These records were incorporated into the analysis and reinforced the interpretation that there is variable accretion in the ASKAP J1745−5051 system.
Distance and classification still depend on new observations
Despite the results presented, the exact distance of ASKAP J1745−5051 is still not precisely defined.
The scientific article reports a wide range, between 0.4 and 9.1 kiloparsecs, which affects more detailed calculations on luminosity and physical properties of the system.
The final classification of the type of cataclysmic variable observed by the researchers also remains open.
The authors indicate that the system seems to be a polar or asynchronous polar, but state that the definition depends on a more reliable measurement of the white dwarf’s rotation period.
These uncertainties are part of the next stages of investigation and should be evaluated by new observations in radio, X-rays, ultraviolet, and visible light.
Among the researchers’ objectives is to better understand the origin of the unusual radio luminosity, the behavior of X-rays, and the relationship between this system and other transients detected in the Milky Way.
The research places ASKAP J1745−5051 as a reference case for future studies on periodic cosmic signals.
From this system, astronomers will be able to compare patterns of radio, X-rays, orbit, and accretion to investigate which phenomena belong to the same physical family and which require different explanations.
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