A dead star is flashing radio waves every 8 minutes, and its partner looks a lot like the sun

Since 2022, astronomers have been investigating a new type of cosmic object known as long-period radio transients. These objects emit bright flashes of radio waves every few minutes to every few hours, and some have been traced back to binary systems consisting of a small, dim red dwarf star orbiting a white dwarf remnant. In a study published in Nature Astronomy, researchers have now discovered the first long-period radio transient involving a star similar to our Sun, alongside a white dwarf.

To uncover this new source, scientists first ruled out the possibility of extremely slow-spinning neutron star pulsars, as their slow rotation shouldn't generate radio waves. Instead, they focused on the binary nature of the system, discovering that a red dwarf star, likely orbiting a white dwarf, was responsible for the radio signals. This pattern emerged across several identified long-period transients, with a binary system of a white dwarf and a small, cool red dwarf being the common characteristic.

In late 2024, researchers from Curtin University used the Murchison Widefield Array radio telescope in Western Australia to search for new long-period transients. They employed a search method developed by PhD student Csanád Horváth, which led to the detection of short flashes of radio waves occurring every 7.9 minutes. However, these signals stopped after a few weeks.

After analyzing the data, the team uncovered a pattern: the pulses only appeared during a six-hour window, followed by 26 hours without pulses. The most plausible explanation for this behavior is that the system is a binary, with two stars orbiting each other once every 32 hours. At this time, the Murchison Widefield Array telescope in South Africa pinpointed the source to a faint star in a specific patch of the sky.

Further analysis using the Keck telescope in Hawai'i revealed that the star was not a diminutive red dwarf but rather a G-type star, similar in mass and temperature to our Sun. To determine the nature of the pulsing object, the research team examined its timing and spectrum. The pulsing object's radio signals showed variations in arrival times, indicating its orbit size.

Additionally, its spectrum "fingerprint" showed minimal wobbling, suggesting that the Sun-like star is significantly heavier than its companion. By combining these calculations, the pulsing object's mass was determined to be about two-thirds that of the Sun, ruling out the possibility of it being a neutron star.

The researchers believe this pulsing object is a white dwarf pulsar, the first discovered in orbit around a Sun-like star. This discovery suggests that such unusual systems may be more common in the universe, but their presence is often obscured by the bright light of the surrounding star. Radio pulses, however, can penetrate this glare, making it possible for radio surveys to uncover a hidden population of white dwarfs orbiting bright stars, which optical and X-ray telescopes often miss.

If more long-period transients prove to be hiding white dwarfs around bright stars, radio surveys could potentially reveal new insights into the lives and deaths of stars like our own Sun. The next generation of radio telescopes, like the SKA Observatory, is expected to detect many more of these systems, offering valuable information about stellar evolution and the universe's expansion.