Just a few years ago, a strange signal was received from the plane of the Milky Way.
It was something astronomers had never seen before, pulsing with a radio beat too slow to fit any known astronomical object.
It may have just come and gone as a one-off anomaly.
But then they found another one.
And another.
To date, around a dozen of these long-period radio transients (LPTs) have been detected from diverse corners of the galaxy, leaving scientists baffled.
Now, a team led by astronomer Kovi Rose of the University of Sydney in Australia thinks they may finally have found their Rosetta Stone, the object that could help them interpret at least some of these weird, pulsating objects.
In the direction of the galaxy's inner regions, the researchers traced an LPT signal directly to a magnetic cataclysmic variable star – a strongly magnetized white dwarf cannibalizing its companion and belching periodic radiation.
"Long-period radio transients have puzzled astronomers for years," Rose says.
"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."
The mystery of the LPTs, first detailed in a 2022 paper, reared its head again after astronomers found something in the plane of the Milky Way pulsing in a weird way.
Every 18.18 minutes, the brightness of an object named GLEAM-X J162759.5−523504.3 increased for 30 to 60 seconds, temporarily making it one of the brightest objects in the low-frequency radio sky.
Then it stopped.
But it wasn't long before astronomers found more – showing that, whatever this strange object was, it wasn't just a one-off weirdness.
As the population grew, astronomers began to piece together possible explanations.
Some observations pointed to highly magnetized white dwarfs, while others hinted that at least some LPTs might arise in binary systems, where a white dwarf interacts with a companion star.
A major breakthrough came in 2025, when one LPT signal, named ILT J1101+5521, was traced to a binary star consisting of a red dwarf and a white dwarf, orbiting so closely together that their magnetic fields repeatedly clashed, sending out periodic bursts of radio waves.
The picture grew even more complicated when astronomers discovered that one LPT, ASKAP J1832-0911, also emitted X-rays, suggesting energetic processes beyond radio emission alone.
But no single object seemed capable of tying all the clues together.
And that's what makes this new discovery so intriguing. Its name is ASKAP J1745-5051, and it's the first object to unite many of the puzzle pieces previously observed in other LPTs.
That includes both radio and X-ray emission, a white dwarf and a binary companion, strong magnetic activity, orbital motion, and accretion – the gravitational transfer of material onto the white dwarf.
"Some similar objects had been linked to binary systems before, but this is the first one where we can clearly see both stars and the accretion process in action," says astrophysicist Tara Murphy of the University of Sydney and the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav).
The discovery was made using CSIRO's ASKAP radio telescope in Wajarri Yamaji Country in Western Australia – one of the world's most sensitive facilities.
Because the system is such a chaos gremlin, it's impossible to tell exactly how far away it is. The best estimates place it between around 1,300 and 30,000 light-years away.
But the data were detailed enough that the researchers could figure out what kind of object it is.
ASKAP observations show a system that flares in radio waves every 81 minutes (1.35 hours), accompanied by matching periodic X-ray emission detected by NASA's Swift observatory and the Einstein Probe X-ray Telescope.
Optical observations obtained using the Southern Astrophysical Research (SOAR) Telescope showed a white dwarf binary at the emission's location in the sky, with spectra revealing a clear orbital period of about 81 minutes – closely matching the period of the radio and X-ray bursts.
These observations reveal that the object is a magnetic cataclysmic variable. Every orbit, the white dwarf pulls material from its red dwarf companion star, which is funneled by the white dwarf's magnetic field onto its surface.
As the material crashes onto the white dwarf, it heats to millions of degrees and emits high-energy radiation – that's the source of the X-ray signal.
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Meanwhile, gas accelerated by the two stars' clashing magnetic fields appears to produce the radio signal, similar to the mechanism proposed for ILT J1101+5521.
It's such a beautiful convergence of characteristics that it could help explain other LPTs that only show some of these traits.
And it's genuinely exciting to be able to observe our understanding of LPTs evolve in real time.
"Each new discovery is helping us piece together the bigger picture," Rose says.
"We're only just beginning to understand this new class of cosmic events."
The research has been published in Nature Astronomy.