Astronomers have found a white dwarf orbiting a Sun-like star that emits radio pulses every 7.9 minutes, the first such system of its kind.
Astronomers have discovered a binary star system that emits bright flashes of radio waves every 7.9 minutes, according to research published in Nature Astronomy. The system, known as GPM J071507−114153, consists of a white dwarf and a G-type star similar to the Sun.
The radio flashes were first spotted in late 2024 using the Murchison Widefield Array radio telescope in Western Australia. The MeerKAT telescope in South Africa pinpointed the source to a tiny patch of sky containing a single faint star, and the Keck telescope in Hawai’i recorded the star’s spectrum.
The spectrum showed the star was not a small, cool red dwarf, but a G-type star almost the same mass and temperature as the Sun. The pulsing object is about two-thirds as heavy as the Sun, which means it is too light to be a neutron star.
The pulses arrive up to four seconds earlier or later than expected as the pulsing object swings around its orbit, because the radio waves have further to travel at some points than others. The pulses only appear during a window of about six hours, followed by 26 hours without pulses. The most natural explanation is that the system is a binary: two stars orbiting each other once every 32 hours, with the radio pulses only visible when they are lined up in the right way.
"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 Sam McSweeney, a scientist with the Square Kilometre Array Observatory.
The discovery marks the first time radio pulses have been detected from a white dwarf orbiting a sun-like star. Previously discovered long-period radio transients typically involved a white dwarf and a small, cool red dwarf.
Researchers believe systems like this are probably quite common in the universe, but white dwarfs next to bright stars are very hard to see because the glare of the bright star hides the faint white dwarf. Radio pulses cut through the glare, so radio surveys could uncover a whole undiscovered population that optical and X-ray telescopes miss.
Some white dwarf binaries are thought to be the ancestors of Type Ia supernovae, which astronomers use as "standard candles" to measure interstellar distances and the expansion of the universe. Finding these systems could reveal more about this process.
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