Astronomers have traced mysterious repeating radio signals from space to an unusual pair of stars located more than 5,000 light-years from Earth. The system, designated GPM J071507−114153, consists of a rapidly rotating white dwarf and a companion star similar to the Sun.
The discovery was made by researchers at the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR). It marks the first time astronomers have detected radio pulses from a white dwarf orbiting a Sun-like star, offering new insights into a rare class of astronomical objects.
White dwarf and Sun-like star form an unusual pairing
The newly identified system contains two stars orbiting each other: a white dwarf, the dense core left behind after a star dies, and a G-type star comparable to the Sun.
The white dwarf produces radio pulses at intervals of approximately eight minutes. Such signals are associated with a class of astronomical objects known as long-period transients (LPTs), which emit radio waves intermittently over periods ranging from minutes to hours.
Around a dozen LPT systems have been identified since the first discovery by the same ICRAR research team in 2021. Although several previously identified systems contain a white dwarf and another star, astronomers have struggled to establish which star produces the radio emissions.
The latest observation provides clearer evidence by revealing the white dwarf’s movement as it orbits its companion.
“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 lead author Dr Sam McSweeney, a commissioning scientist with the Square Kilometre Array Observatory (SKAO).
Radio signals reveal stellar activity thousands of light-years away
The researchers analysed more than 100 hours of radio observations using the Pawsey Supercomputing Research Centre to validate and understand the white dwarf’s orbital movement.
The observations also revealed activity on the companion star. Associate Professor Natasha Hurley-Walker, a co-author of the study, said the white dwarf’s radio pulses helped the team detect stellar flares on the Sun-like star. These flares are similar to the solar activity responsible for producing auroras on Earth.
The team also observed the white dwarf moving behind a region with a strong magnetic field, which they believe is likely to be a stellar prominence. Such structures are large loops of plasma that erupt 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 5000 light-years away.”
Multiple observatories helped identify the star system
The discovery began with a large survey conducted using the Murchison Widefield Array (MWA), which scans the Milky Way visible from Australia. Researchers subsequently used South Africa’s MeerKAT radio telescope to establish the system’s precise location.
Optical observations from the W. M. Keck Observatory in Hawaii then confirmed its association with a G-type star.
The research involved several radio astronomy facilities that also serve as precursors to the Square Kilometre Array telescopes. These include the MWA at the CSIRO Murchison Radio-Astronomy Observatory in Western Australia and MeerKAT, operated by the South African Radio Astronomy Observatory.
Discovery offers a preview of future radio astronomy capabilities
The identification of GPM J071507−114153 adds to the growing number of known long-period transient systems and provides stronger evidence about the origins of their radio emissions.
Researchers expect future observations to help establish how these unusual stellar pairs generate their signals and how their magnetic environments influence the process.
Dr McSweeney said, “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.”
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