Scientists Find Zombie Star That Sends a Signal Every 7.9 Minutes

Illustration: ZME Science. The signal lasts less than four seconds. Then, roughly eight minutes later, another burst can arrive; and another, and another.

For about six hours, the strange cosmic heartbeat repeats. Then it falls silent for more than a day before resuming the cycle. Astronomers have now traced this bizarre rhythm to a stellar corpse orbiting a star remarkably similar to our Sun.

And the living star next door may hold the secret to why the dead one keeps broadcasting. The zombie star that just won’t stay quiet The object has the decidedly unromantic name GPM J071507−114153, or J0715−1141 for short. Astronomers first spotted it on December 4, 2024, using the Murchison Widefield Array , a sprawling radio telescope in Western Australia.

Something in the Milky Way was producing exceptionally brief radio bursts at surprisingly regular intervals. The pulses were separated by approximately 474 seconds — 7 minutes and 54 seconds. The timing offered the first clue.

Ordinary stars can’t spin that fast, they’d just tear themselves apart. Whatever was generating the signals had to be extraordinarily compact. There were two main suspects: a neutron star , the ultradense remnant of a massive stellar explosion, or a white dwarf , the leftover core of a star that has exhausted its nuclear fuel.

White dwarfs are sometimes called zombie stars . They no longer generate energy through ordinary nuclear fusion, but they remain hot, dense, and capable of some extraordinary behaviour. Our own Sun will eventually become one, after shedding its outer layers billions of years from now. × Researchers suspected a white dwarf was more likely, but they needed the proof.

Illustration showing how a white dwarf forms. Listening to the stars Over the following months, the Australian telescope recorded 214 radio pulses. Additional observations with South Africa’s MeerKAT radio telescope helped astronomers pinpoint their origin and study their arrival times with greater precision.

That’s when they spotted another pattern. The star’s radio activity followed a second, much slower clock. Approximately every 32.5 hours, the signals became detectable during a window lasting around six hours.

Outside that window, the source generally disappeared from the radio observations. A stellar zombie sending out a regular pulse is weird enough, but two? The only answer, astronomers suspected, was that it isn’t alone.

A zombie with a companion A team led by Samuel J. McSweeney from Curtin University went to another telescope, the powerful Keck Observatory in Hawaii. Whereas the other two observers tracked radio pulses, the Keck Observatory offered a look at the system in visible light.

Using spectroscopy , Keck split the star’s light into its component wavelengths, revealing a stellar fingerprint that matched a G-type star , remarkably similar to our Sun. This was the companion, not the zombie star. The zombie star is too faint to observe in the visible spectrum.

The visible star has an estimated mass about 94% that of the Sun and a surface temperature of roughly 5,500 Kelvin. It is a relatively ordinary star, except for its decidedly extraordinary companion. The researchers concluded that the system consists of a white dwarf and a Sun-like star orbiting one another roughly every 1.35 days.

This explains the two tempos. The eight-minute rhythm is the white dwarf’s rotation. The 32.5-hour cycle is interpreted as the time it takes the stellar pair to complete an orbit.

Illustration: ZME Science. “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 and commissioning scientist with the Square Kilometre Array Observatory, Dr.

Sam McSweeney Already, it would be a very cool discovery. But the team didn’t stop there. The radio signals could be showing storms on another star Our Sun is surrounded by an atmosphere of extraordinarily hot, electrically charged gas called the corona.

This plasma is shaped by magnetic fields that can form enormous loops, erupt in flares, and sometimes send vast clouds of charged particles hurtling into space. The companion of J0715−1141 looks pretty similar to the Sun and it probably has its own magnetic activity. And the white dwarf’s radio pulses may be passing through parts of that magnetic environment on their way to Earth.

The researchers noticed that the polarization of the signals — the orientation of their electromagnetic waves — changed in ways that appeared to depend on the stars’ orbital positions. This is relevant because magnetized plasma can twist the polarization of radio waves through a phenomenon called Faraday rotation.

In effect, the radio pulses act like probes passing through the outer atmosphere of a distant star. The team suggests that it may be possible to detect enormous magnetic structures resembling solar prominences — loops of plasma extending from a star’s surface. “As a bonus, we also saw the white dwarf moving behind a region with a strong magnetic field, most likely a ‘stellar prominence’, which is a large loop of plasma erupting from a star’s surface,” said Associate Professor Natasha Hurley-Walker, co-author on the paper.

“It’s amazing that by using radio wavelengths we can detect the storms on a star over 5000 light-years away.” Radio pulses from a rapidly spinning white dwarf pass through the hot, magnetized corona of its Sun-like companion. The charged plasma may alter the signals’ polarization, offering astronomers a rare glimpse into the magnetic activity and space weather of a distant star.

But what’s making the pulses? This is all neat and interesting, but the biggest question remains unanswered. What actually produces the powerful radio pulses?

J0715−1141 belongs to an emerging category called long-period transients . These unusual objects produce intense, often highly polarized radio signals at intervals ranging from minutes to hours. Astronomers have only uncovered about a dozen of them, so their underlying physics is not entirely clear.

They’re also quite different from one another. Some resemble pulsars, rapidly spinning neutron stars whose radio beams sweep across space like lighthouse beams. But many long-period transients pulse far more slowly than conventional radio pulsars.

For white dwarfs, one idea is that the interaction between a spinning white dwarf’s magnetic field and material supplied by its companion can accelerate charged particles, producing coherent radio emission. That’s plausible, but far from proven. But this system is a particularly interesting testing site, because of the companion.

This companion could be more than a passive spectator. Its stellar wind or magnetic environment may provide ingredients essential to the pulses. But there’s also the mystery of how this stellar pair came to be in the first place.

The scientists suspect the white dwarf’s progenitor once expanded into a giant star, engulfing the companion in an enormous shared envelope of gas. As the stars interacted with this material, their orbit shrank dramatically. Eventually, the envelope was expelled, leaving behind the compact white dwarf and its Sun-like neighbour in a tight orbit.

A work in progress More sensitive radio observations, particularly with the upcoming Square Kilometre Array telescopes, could reveal many more such objects. Each one may help astronomers understand how dead stars behave, how magnetic fields interact across binary systems, and why some stellar remnants refuse to fade quietly into the background.

The most fascinating thing about this zombie star may not be that it keeps broadcasting after its former life has ended. It’s that every brief pulse could be telling us something about the star that’s still alive beside it. The study was published in Nature Astronomy .