Imagine staring into the vastness of space, only to be met with a cosmic mystery: slow, rhythmic pulses of radio waves, repeating every few minutes or hours, defying everything we thought we knew about the universe. These enigmatic signals, known as long-period transients, have baffled astronomers since their discovery in 2022. But here’s where it gets even more intriguing: our new study, published today in Nature Astronomy, might just crack the code. And this is the part most people miss—it’s not just about solving a puzzle; it’s about rewriting the rules of astrophysics.
Radio astronomers are no strangers to pulsars, those rapidly spinning neutron stars that emit beams of radio waves like cosmic lighthouses. But long-period transients are different. While the slowest pulsars spin in mere seconds, these newcomers take their time, with periods ranging from 18 minutes to over six hours. The catch? According to our understanding of neutron stars, they shouldn’t be able to produce radio waves at such slow speeds. So, is our physics flawed, or is there something else at play?
Enter white dwarfs—the unsung heroes of this story. These Earth-sized remnants of dead stars, packing the mass of an entire Sun, might just be the culprits behind these mysterious signals. Our study presents compelling evidence that GPM J1839-10, the longest-lived long-period transient, is actually a white dwarf star paired with a stellar companion. But here’s where it gets controversial: could these slow pulses be the work of white dwarf pulsars, a phenomenon we’ve only recently confirmed exists?
White dwarfs, on their own, don’t emit radio pulses. But when paired with an M-type dwarf in a binary system, they can create the perfect conditions for radio emission. The first such “white dwarf pulsar” was confirmed in 2016, raising a tantalizing question: are long-period transients simply the slower cousins of these pulsars?
To date, over ten long-period transients have been discovered, but their extreme distance and deep galactic embedding have made identification tricky. Only in 2025 were two of them conclusively identified as white dwarf–M-dwarf binaries—a revelation that left astronomers with more questions than answers. Do these binaries radiate the same way as their faster counterparts? And will the ones visible only in radio wavelengths forever remain a mystery?
What we needed was a model that could bridge the gap—and a long-period transient with enough high-quality data to test it. Enter GPM J1839-10, a 21-minute period transient discovered in 2023. Unlike its predecessors, this one is uniquely long-lived, with pulses detected in archival data dating back to 1988. Using a “round-the-world” observation strategy with telescopes in Australia, South Africa, and the United States, we uncovered a pattern that’s anything but random: pulses arrive in groups of four or five, paired and separated by two hours, repeating every nine hours.
This stable pattern strongly suggests a binary system, where two bodies orbit each other every nine hours. By analyzing the data, we were able to refine the orbital period to an astonishing precision of 0.2 seconds. But here’s the real kicker: the peculiar ‘heartbeat’ pattern of these pulses can only be explained by a white dwarf’s magnetic pole sweeping through its companion’s stellar wind—a phenomenon observable only in radio signals.
Our model not only explains GPM J1839-10 but also predicts variability in optical data, which other astronomers have already confirmed. While the exact emission physics is still under study, this breakthrough is a giant leap toward understanding long-period transients. But we want to hear from you: do you think white dwarfs are the key to solving this cosmic mystery, or is there another explanation waiting to be discovered? Let us know in the comments!
