Scientists have traced mysterious radio signals to a binary star system 1,600 light-years away in the constellation Ursa Major, near the Big Dipper.
For a decade, Earth has been receiving these regular pulses every two hours, or precisely every 125 minutes.
Researchers have now determined these signals originate from an extraordinary cosmic partnership.
A white dwarf and red dwarf star orbit each other so closely that their magnetic fields interact, creating radio pulses that travel across space to reach our planet - named ILTJ1101.
Artist's impression of red and white dwarf planets
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Dr Iris de Ruiter, now at the University of Sydney, first discovered these mysterious pulses in 2024 whilst examining archival data from the Netherlands.
She was sifting through information from the Low Frequency Array (LOFAR), the largest radio telescope operating at the lowest observable frequencies from Earth.
Initially, Dr de Ruiter found a single pulse that had arrived at Earth in 2015 but further investigation of the same area of sky revealed six more pulses.
What made these signals particularly intriguing was their duration - lasting between a few seconds to a minute - and their remarkably regular intervals.
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This pattern of slow, regular pulses remains rare in astronomical observations, even as detection of 'fast radio bursts' has increased.
Initially, only one star was visible—a red dwarf, which is a small, cool star that can burn for trillions of years.
Dr Kilpatrick noted: "The spectroscopic lines in these data allowed us to determine that the red dwarf is moving back and forth very rapidly with exactly the same two-hour period as the radio pulses."
This wobbling motion revealed the presence of a second, hidden star - a white dwarf.
These dead stars, having burned through all their nuclear fuel, are typically too dim to observe directly. As these stellar companions orbit each other, their magnetic fields "bump together" to create the radio pulses.
Dr Kilpatrick explained the distinction between these pulses and other cosmic phenomena: "The radio pulses are very similar to FRBs, but they each have different lengths.
Image of a red giant and white dwarf (Stock)
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"The pulses have much lower energies than FRBs and usually last for several seconds, as opposed to FRBs which last milliseconds."
These longer radio emissions represent a different class of cosmic event than the millisecond-long fast radio bursts that have fascinated astronomers in recent years.
Scientists are still investigating whether these phenomena exist on a continuum or represent distinct types of cosmic events.
Dr Kilpatrick believes this discovery will inspire other astronomers to consider binary systems as possible sources of unusual radio pulses.
"This confirms the leading hypothesis for the white dwarf binary origin and is the first direct evidence we have for the progenitor systems of long-period radio transients," he said.
