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By Rodrigo Santos Andrade
A dead star is flashing radio waves every 8 minutes, and its partner looks a lot like the Sun
visibility comment0 event November 12, 2026 timer 07:06
Slowly blinking radio signals from space have puzzled astronomers since 2022.
Curtin University, CC BYSince 2022, astronomers have been puzzling over a new kind of cosmic object called long-period radio transients.
These are objects that emit bright flashes of radio waves into space every few minutes to every few hours.
Some have been traced back to binary systems of a small, dim cool star called a red dwarf in orbit with a star remnant called a white dwarf.
In new research published today in Nature Astronomy, we report the first discovery of a different source for one of these enigmatic intermittent broadcasters: it still involves a white dwarf, but also a star much like our own Sun.
The search for sources
After the discovery of the first long-period radio transient in 2022, once we had ruled out aliens, we went looking for natural explanations.
One idea was that they were extremely slow-spinning neutron star pulsars, the collapsed cores of enormous stars which also send out repeating radio flashes. But in theory a neutron star spinning that slowly shouldn’t produce radio waves, so the answer had to be something else.
When we started traced these radio signals back to their sources, we made a breakthrough. One of our repeating signals came from a red dwarf star, probably orbiting a white dwarf (the remnant of a star like our Sun).
Across the handful of long-period transients whose source stars we can identify, a pattern has emerged: a binary system of a white dwarf and a small, cool red dwarf.
The source of the newly discovered long-period radio transient is precisely located to a G-type star like the Sun.
Stellarium / PanSTARRS, CC BY
A signal from the wrong kind of star
In late 2024, we were looking for new long-period transients using the Murchison Widefield Array radio telescope in Western Australia.
Using a search method developed by PhD student Csanád Horváth, we spotted something: short flashes of radio waves, arriving like clockwork every 7.9 minutes.
Then the flashes stopped. For weeks we saw nothing, and we nearly gave up. But when we plotted every detection and non-detection together, a pattern emerged.
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.
The MeerKAT telescope in South Africa pinpointed the source to a tiny patch of sky containing a single faint star. We turned to the Keck telescope in Hawai’i to record the star’s spectrum – the “fingerprint” of its light, which can tell us a lot about the star itself.
The result was a surprise: this was not a tiny red dwarf, but a G-type star almost the same mass and temperature as our own Sun.
How we discovered the new object, and how it connects to long-period radio transients.
Weighing a star we can’t see
How can we be sure our source isn’t a neutron star after all?
The clue is in the timing. As the pulsing object swings around its orbit, the pulses arrive up to four seconds earlier or later than expected, because the radio waves have further to travel at some points than others. That tells us how large the orbit is.
The precise spectrum “fingerprint” of the Sun-like star shows it barely wobbles as the pulsing object orbits around it. This means the Sun-like star must be much heavier than its partner.
When we combine the calculation of the size of the orbit, how long each orbit takes, and the spectrum measurements, we can work out that the pulsing object is about two-thirds as heavy as the Sun. That means it’s too light to be a neutron star.
We believe the pulsing object is a white dwarf pulsar, the first found in orbit around a Sun-like star.
What strange systems are hiding in the dark?
How did this odd couple come to be? We think the star that became the white dwarf must have first swelled into a giant, engulfing its companion, which spiralled inward and shrank the orbit before the giant’s outer layers were ejected.
We think systems like this are probably quite common in the universe, but white dwarfs next to bright stars are very hard to see. The glare of the bright star hides the faint white dwarf.
Radio pulses, on the other hand, cut through the glare. If more long-period transients turn out to be hiding white dwarfs around bright stars, radio surveys could uncover a whole undiscovered population that optical and X-ray telescopes miss.
This is important because some white dwarf binaries are thought to be the ancestors of Type Ia supernovae. Astronomers use these exploding stars as “standard candles” – reference points to measure interstellar distances and the expansion of the universe. Finding these systems could reveal more about this process.
With the next generation of radio telescopes, such as the SKA Observatory, we expect to find many more. And if we can find these objects around many different types of stars, it will give us insights into the lives and deaths of stars like our own Sun, across our galaxy and beyond.
Natasha Hurley-Walker receives funding from the Australian Research Council. The research behind this work was carried out at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. The author acknowledges the Wajarri Yamaji as the Traditional Owners and Native Title Holders of the observatory site.
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