Imagine receiving mysterious signals from the depths of space, signals that repeat every few minutes or hours, leaving scientists scratching their heads. These puzzling slow radio pulses have baffled astronomers since their discovery in 2022, but a groundbreaking study published today in Nature Astronomy might finally shed some light on this cosmic enigma. [https://doi.org/10.1038/s41550-025-02760-y]
We’re all familiar with pulsars—those rapidly spinning neutron stars that emit radio beams like cosmic lighthouses. But here’s where it gets intriguing: the slowest pulsars complete a rotation in just a few seconds. So, when astronomers detected long-period transients with periods ranging from 18 minutes [https://theconversation.com/this-object-in-space-flashed-brilliantly-for-3-months-then-disappeared-astronomers-are-intrigued-175240] to over six hours [https://doi.org/10.1038/s41550-024-02452-z], it defied everything we thought we knew about neutron stars. After all, they shouldn’t be able to produce radio waves while spinning so slowly. Is our understanding of physics flawed?
But here’s the twist: what if neutron stars aren’t the stars of this story? Our new research suggests that the longest-lived long-period transient, GPM J1839-10 [https://doi.org/10.1038/s41586-023-06202-5], is actually a white dwarf star—a stellar remnant about the size of Earth but packing the mass of an entire Sun. And it’s producing powerful radio beams with the help of a stellar companion, hinting that others might be doing the same.
Enter white dwarf pulsars—a concept that’s both fascinating and controversial. While no isolated white dwarf has been observed emitting radio pulses, they can do so when paired with an M-type dwarf (a star about half the Sun’s mass) in a close binary system. In fact, the first rapidly spinning white dwarf pulsar was confirmed in 2016 [https://doi.org/10.3847/2041-8205/831/1/L10]. This raises a bold question: Could long-period transients be the slower cousins of these white dwarf pulsars?
And this is the part most people miss: over ten long-period transients have been discovered, but their extreme distance and deep embedding in our galaxy have made identification challenging. Only in 2025 were two such transients [https://theconversation.com/astronomers-have-pinpointed-the-origin-of-mysterious-repeating-radio-bursts-from-space-244920] conclusively identified as white dwarf–M-dwarf binaries [https://theconversation.com/mysterious-radio-pulses-from-space-have-been-tracked-down-and-the-source-is-not-what-astronomers-expected-250251]. Yet, this discovery left astronomers with more questions than answers. Do these binaries radiate like their faster counterparts? And will the long-period transients visible only at radio wavelengths remain a mystery forever?
To crack this code, we needed a model that works for both types of systems and a long-period transient with enough high-quality data to test it. Enter GPM J1839-10, a uniquely long-lived transient with a 21-minute period, discovered in 2023. Unlike its predecessors, pulses from this object were found in archival data dating back to 1988, though not consistently. Located 15,000 light-years away, it’s only visible in radio waves, so we embarked on a global observation campaign using telescopes in Australia (ASKAP) [https://www.csiro.au/en/about/facilities-collections/atnf/askap-radio-telescope], South Africa (MeerKAT) [https://www.sarao.ac.za/science/meerkat/about-meerkat/], and the United States (Karl G. Jansky Very Large Array) [https://science.nrao.edu/facilities/vla].
What we found was astonishing: the seemingly random signal wasn’t random at all. The pulses arrived in groups of four or five, with pairs separated by two hours, repeating every nine hours. This stable pattern strongly suggests a binary system with two bodies orbiting each other every nine hours—a white dwarf and an M-dwarf, to be precise. By refining the orbital period to an astonishing precision of 0.2 seconds, we confirmed this hypothesis.
But here’s where it gets even more intriguing: the peculiar “heartbeat” pattern of the pulses offers clues to the system’s nature, something only radio signals can reveal. Inspired by a previous study [https://doi.org/10.1093/mnras/sty2407], we modeled GPM J1839-10 as a white dwarf generating a radio beam as its magnetic pole sweeps through its companion’s stellar wind. This model accurately predicts the heartbeat pattern and even allows us to reconstruct the system’s geometry, including the distance between the stars and their masses.
GPM J1839-10 could be the missing link between long-period transients and white dwarf pulsars, but the debate is far from over. Armed with our model, other astronomers [https://doi.org/10.1093/mnrasl/slaf101] have detected variability at our measured periods in optical data, though the binary pair remains indistinguishable. While research continues into the emission physics and the broader properties of long-period transients, this study marks a crucial step toward unraveling the mystery.
But here’s the controversial part: Are we truly on the right track, or could there be another explanation lurking in the cosmic shadows? What do you think? Could white dwarf binaries be the key to understanding these slow radio pulses, or is there more to the story? Let’s spark a discussion in the comments!
