Astronomers in Australia have identified a peculiar star system, approximately 5,000 light-years from Earth, that emits regular radio signals every eight minutes. This newly discovered system, designated GPM J071507−114153, consists of a white dwarf—the dense remnant of a dead star—orbiting a star similar to our sun.
This marks the first detection of radio pulses from a white dwarf in orbit around a sun-like star, according to a study published in Nature Astronomy. Researchers at the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia, noted that such pulses are typically observed in systems with smaller, cooler red dwarf stars, making this discovery significant.
"This is the first time the pulses are clear enough to see the white dwarf moving in its orbit around its companion," said study lead author Dr. Sam McSweeney. "So we know that the pulsations are coming from a region close to the white dwarf, or possibly even from the white dwarf itself."
McSweeney explained that these types of stellar pairs belong to a class of objects known as long-period transients (LPTs), which produce radio signals that switch on and off at intervals ranging from minutes to hours. The first LPT was discovered by the same ICRAR team in 2021, and about a dozen have been found since, though their origin has remained unclear.
Previously, it was uncertain which star in binary LPT systems generated the radio pulses. The ICRAR team analyzed over 100 hours of radio data, utilizing the Pawsey Supercomputing Centre, to confirm the white dwarf's orbital motion. Associate Professor Natasha Hurley-Walker, a co-author of the study, stated that the pulses from the white dwarf allowed the team to observe stellar flares on the sun-like star, similar to Earth's auroras.
"As a bonus, we also saw the white dwarf moving behind a region with a strong magnetic field, most likely a ‘stellar prominence’ – which is a large loop of plasma erupting from a star’s surface," Hurley-Walker said. "It’s amazing that by using radio wavelengths we can detect the storms on a star over 5,000 light-years away."
The LPT was initially detected using the Murchison Widefield Array in Australia, with follow-up observations from the MeerKAT radio telescope in South Africa pinpointing its location. The W.M. Keck Observatory in Hawaiʻi confirmed the system's association with a G-type star through optical observations.
"If we are already making such discoveries with precursor telescopes, just imagine how many more star systems we will be able to find, and what a beautifully detailed view of their signals we will have, once the SKAO telescopes are completely built," McSweeney added.