Astronomers in Australia have identified the source of strange radio pulses arriving from deep space every eight minutes, tracing them to an unusual star system 5,000 light-years from Earth.
The system, called GPM J071507−114153, contains two stars locked in orbit around each other: a white dwarf, the dense remnant left behind after a star dies, and a G-type star similar to our own sun. It marks the first time radio pulses have been detected coming from a white dwarf orbiting a sun-like star, according to a study published in the journal Nature Astronomy.
Researchers at the International Centre for Radio Astronomy Research (ICRAR) in Perth, Western Australia, said this kind of pulsing behavior is typically seen in systems involving smaller, cooler red dwarf stars, which makes the new find notable.
“This is the first time the pulses are clear enough to see the white dwarf moving in its orbit around its companion, so we know that the pulsations are coming from a region close to the white dwarf, or possibly even from the white dwarf itself,” said study lead author Dr. Sam McSweeney, who made the discovery while working as a researcher at ICRAR.
Dr. McSweeney said such pairs fall into a broader category called long-period transients, or LPTs, which emit radio signals that switch on and off over periods ranging from minutes to hours. Roughly a dozen of these systems have been found since the same ICRAR team discovered the first one in 2021, and scientists are still working to understand what drives them.
Earlier LPT discoveries had also shown a white dwarf paired with another star, but it was never clear which of the two was actually producing the radio pulses. To nail that down, the research team processed more than 100 hours of radio data at the Pawsey Supercomputing Research Centre to confirm and study the white dwarf’s motion.
Catching storms on a distant star
Study co-author Associate Professor Natasha Hurley-Walker said the pulses from the white dwarf also let the team detect stellar flares on the sun-like companion star, similar to the flares that produce aurorae on Earth.
“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 system was first spotted in a large sky survey using the Murchison Widefield Array to scan the portion of the Milky Way visible from Australia. Researchers then used the MeerKAT radio telescope in South Africa to pin down its exact position. The W.M. Keck Observatory in Hawaiʻi later confirmed, through optical observations, that the signal was associated with a G-type star.
Dr. McSweeney said the discovery hints at more to come as bigger instruments go online. “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,” he said.
