A Mysterious Radio Signal Repeats Every 8 Minutes. Astronomers Finally Know What’s Behind It

As astronomers survey the universe, they often encounter signals without a clear source. Although they usually find the source, some answers are weirder than others—take, for example, the mysterious pulses from a star that’s already dead. Beginning in late 2024, the Murchison Widefield Array (MWA) in Australia detected GPM J071507−114153, a radio signal that pulsated roughly every eight minutes. From December 2024 to September 2025, the MWA detected 214 pulses from the source, and astronomers classified the signal as a long-period transient. In a study published today in Nature Astronomy, researchers reported the most likely source for this signal: a binary star system consisting of one white dwarf—the leftover core from a star’s death—and a G-type star like our Sun. The astronomers say it’s the first detection of radio pulses emanating from a white dwarf orbiting a Sun-like star rather than a red dwarf. “It’s amazing that by using radio wavelengths we can detect the storms on a star over 5,000 light-years away,” Natasha Hurley-Walker, a corresponding author of the study and an astronomer at Curtin University in Australia, said in a statement. Beeps from space Long-period transients are a relatively new category of space signals. Scientists first got wind of this type of radiation in 2005, but it was in 2022 that the community really started to study long-period transients. A careful review of the 2022 signal—by a team including several researchers behind the new study—revealed it was distinct from pulsars, which are fast-spinning neutron stars that emit rapid beams of light. The most obvious sign was that long-period transients—as their name suggests—had much longer pulsating periods. The 2022 discovery had a period of roughly 18 minutes, whereas a year later astronomers found another signal with a pulsation period of 21 minutes. This then raised the question of what was creating these long pulses. Dead echoes While there were small differences, researchers found that at least four out of 12 known long-period transients were binary systems composed of a white dwarf and a red dwarf. However, it was less clear which star was responsible for the long radio pulses. But after 100 hours of processing radio data on GPM J071507−114153, the team realized this particular signal was an observational breakthrough. “This is the first time the pulses are clear enough to see the white dwarf moving in its orbit around its companion,” Sam McSweeney, the study’s lead author and an astronomer at Curtin University in Australia, said in the statement. “[S]o we know that the pulsations are coming from a region close to the white dwarf, or possibly even from the white dwarf itself.” What’s more, the pulses from the white dwarf helped the team to catch stellar flares on its Sun-like companion, Hurley-Walker added. Follow-up optical observations with the Keck Observatory confirmed that the other object was indeed a G-type star. In this way, future long-period transient detections might allow us to find white dwarfs hidden from traditional observatories, the team added in the paper.