Astronomers Detected a Radio Signal Coming Directly From an Exoplanet for the First Time

The auroral signal reveals a magnetic field thousands of times stronger than Earth’s.

22 Sep 2026, 20:08 by Tibi Puiu · ZME Science

The South African MeerKAT radio telescope, situated 90 km outside the small Northern Cape town of Carnarvon, is a precursor to the Square Kilometre Array (SKA) telescope and will be integrated into the mid-frequency component of SKA Phase 1. Credit: MeerKAT

For many years, astronomers have listened for the radio crackle of planets beyond the Solar System. They may finally have isolated one.

The source is Beta Pictoris b, a young gas giant about 64 light-years away. And despite what “radio signal from an exoplanet” may suggest, this is not a message from aliens. The signal appears to come from an aurora — the same broad family of magnetic phenomena that produces Earth’s beautiful northern and southern lights and Jupiter’s powerful radio bursts.

In other words, the radio signal is owed to some natural phenomena.

Using South Africa’s MeerKAT array, researchers observed the Beta Pictoris system four times in 2025 and 2026. Each time, they picked up radio emission, including short bursts that brightened and faded rapidly. The signal spanned a broad range of radio frequencies and had an especially revealing property: much of it was circularly polarized, meaning the radio waves corkscrewed through space rather than oscillating in a single direction. This twisting pattern is a hallmark of the kind of radio emission produced by auroras around strongly magnetized worlds.

This phenomenon is called the electron cyclotron maser instability, or ECMI, in which energetic electrons moving through a magnetic field generate intense radio waves. The study, posted September 15 as an arXiv preprint and not yet peer reviewed, would mark both the first radio emission securely localized to an exoplanet and the first direct measurement of an exoplanet’s magnetic-field strength.

Pinning the signal on a planet

Image taken with ESO’s Very Large Telescope showing Beta Pictoris d, orbiting the star Beta Pictoris. Credit: ESO/B. Sutlieff, M. Bonse et al.

Beta Pictoris b is an unusually favorable target for picking up radio signals from far out in space. It is roughly 12 times Jupiter’s mass and orbits about 10 astronomical units from its young star, roughly Saturn’s distance from the Sun. More importantly, the planet appears far enough from its star on the sky that MeerKAT can, with careful measurements, distinguish the two.

Astronomers have previously found intriguing radio emissions from planet-hosting systems. But they could not unambiguously tell whether the planet or its star was responsible.

What’s different this time is that the researchers used nine quasars with positions measured by Gaia, plus a precisely located radio calibrator, as fixed reference points. By comparing the radio signal’s position with the precisely known locations of the star and its planets, the researchers could trace it to Beta Pictoris b itself. The signal lined up with planet b and was far enough from the star and planet c that the team could confidently rule them out as the source.

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The radio waves also act as a magnetometer. With ECMI, the highest frequency depends directly on the magnetic field where the radiation originates. Because the bursts reached 3.5 gigahertz — the top of MeerKAT’s observing band — the field must be at least about 1,250 gauss at the emission site. Earth’s surface field is roughly half a gauss.

Short, repeated radio bursts detected from planet Beta Pictoris b. Credit: Ceballos et al., arXiv, 2026

“It’s an incredibly, incredibly strong magnetic field, much stronger than anything in our solar system,” astronomer Yvette Cendes told Science News.

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And 1,250 gauss is a lower limit. The planet could be emitting at still higher frequencies that these observations did not cover.

A search that kept coming up empty

Astronomers have tried for years to catch this kind of planetary radio glow. A 2022 pilot search of eight directly imaged exoplanets with the Very Large Array came up empty. A 2024 search aimed specifically at Beta Pictoris b, this time at 250 to 500 megahertz, also found nothing. Meanwhile, observations of ultracool dwarfs had already revealed planet-like auroral radio emission, suggesting that massive planets might produce something similar.

Beta Pictoris b may have succeeded where those searches failed because it is a magnetic heavyweight. This makes it easier to distinguish from other background sources. It also spins quickly, once every eight to nine hours. During one MeerKAT observation, the first and third bursts arrived about eight hours apart, tantalizingly close to the planet’s rotation period. The authors suggest that its rapid spin drives electrical currents between the magnetosphere and upper atmosphere, powering the radio aurora.

They also tested other possible engines. Radiation powered by the star’s wind fell short of the observed power by about three orders of magnitude. Meanwhile, an interaction with a hypothetical moon — something like Io’s influence on Jupiter — remained more than an order of magnitude too weak.

The discovery matters less for its auroral spectacle than for the new window it could open onto distant planets. Magnetic fields shape how atmospheres interact with stellar winds and carry information about processes deep inside planets. A 2024 review of exoplanet radio astronomy described direct planetary radio emission as one of the field’s major outstanding targets.