First Radio Signal Ever Detected From an Exoplanet

Astronomers have detected the first radio signal ever traced directly to a planet outside the solar system. The source is Beta Pictoris b, a gas giant orbiting a young star sixty-three light-years from Earth, and the radio signal indicates a magnetic field far more intense than anything measured on a planet in our solar system.

The finding, posted September 15 to the preprint platform arXiv and reported by CNN's Jacopo Prisco, describes a repeating radio signal picked up by the MeerKAT array in South Africa. Each burst in the radio signal appears to originate from the planet itself rather than its host star, a distinction earlier studies could never confirm.

An unexpected catch in a routine survey

The detection came out of a survey that Edo Berger, a professor of astronomy at Harvard University and a researcher at the Center for Astrophysics | Harvard & Smithsonian, described as something of a fishing expedition. The team had been hunting for the faint radio signatures of exoplanet magnetic fields on the assumption that such fields would resemble Jupiter's. What they found was a radio signal far stronger than the models predicted.

According to CNN, the find landed in the lap of doctoral researcher Kevin Ortiz Ceballos, the study's lead author, who spotted the pattern while reviewing data collected across four observing sessions between early 2025 and mid-2026. The MeerKAT array, sixty-four dishes spread across South Africa's Karoo desert, recorded the radio signal as rapid, recurring bursts plus a fainter persistent glow, all of them highly circularly polarized. The radio signal spanned frequencies from 0.85 to 3.5 gigahertz.

Pinpointing the source took extra care. Because past claims of exoplanet radio signals could not rule out the host star as the true origin, the team used distant quasars as fixed reference points to localize each burst. Beta Pictoris b matched the position of the emission; the star did not, and no known process in that type of star could explain what they saw, according to the paper.

The study, coauthored by Ortiz Ceballos, Berger, and Yvette Cendes of the University of Oregon, is currently undergoing peer review, which the researchers expect to take several more months. Outside experts who reviewed the preprint found the result compelling while urging caution. Joseph Callingham, an associate professor at the Anton Pannekoek Institute for Astronomy of the University of Amsterdam, said in an email that "what is unique for this study is that they localise the emission to the planet itself, separate from the star."

What the radio signal says about the planet

Astronomers classify this kind of radio signal as auroral radio radiation, the same family of signals produced by Jupiter and Saturn. Charged particles spiral along a planet's magnetic field lines and give off radio waves alongside visible auroras, the same physics behind Earth's northern lights. The mechanism identified in the paper is the electron cyclotron maser instability, whose highest emitted frequency is set by the magnetic field strength at the source.

That relationship allowed the researchers to work backward from the radio signal to the field itself. The top of the observed frequency band implies a magnetic field of at least 1.25 kilogauss where the radio waves are generated. For comparison, Berger said the planet's magnetic field is "at least 200 times stronger than the magnetic field of Jupiter," and Jupiter's field is already powerful enough to power the largest structure in the solar system, a magnetosphere stretching millions of miles toward the sun.

This is the first direct measurement of a magnetic field on any exoplanet. Previously, astronomers could only estimate such fields from theoretical models. The new number lands close to predictions for young, massive gas giants. Beta Pictoris b packs roughly ten to twelve times the mass of Jupiter, completes a full day in only eight to nine hours, and still radiates substantial heat from its interior. Vigorous convection combined with rapid rotation could drive a powerful magnetic dynamo.

The field is more than a curiosity. Planetary magnetic fields act as shields that deflect the stellar wind, the continuous outflow of charged particles from a star that can strip away an atmosphere over time. Earth's own magnetic field is a major reason the planet still holds onto its air. Extending this kind of radio signal measurement to more distant planets would tell scientists which worlds keep their atmospheres and which do not.

Why scientists are excited, and staying careful

The Beta Pictoris system ranks among the most scrutinized planetary systems in the sky. The star is only about twenty-three million years old, a newborn next to our own 4.5-billion-year-old solar system, and it is 1.75 times as massive as the sun. The planet Beta Pictoris b was discovered in 2008; two siblings, Beta Pictoris c and Beta Pictoris d, followed in 2019 and this year. The system is also known for a giant disk of dust and debris, photographed in detail by NASA's Hubble Space Telescope in 2015.

Jonathan Nichols, a professor of planetary auroras at the University of Leicester, said the finding could open a new window onto distant worlds. "Auroral radio emissions are important because they allow us to understand how an object interacts with its local space environment," he wrote in an email to CNN. Such radio signals, he explained, make it possible to infer properties of a planet that no other technique can measure directly.

Callingham offered a concrete test that could settle the matter: if future bursts in the radio signal repeat in step with the planet's rotation period, the auroral explanation gains direct support. "It's probably auroral," he told Science News, calling the evidence "so TBD, but, compelling." The authors have requested additional telescope time to keep watching Beta Pictoris b and to investigate why its magnetic field runs so strong, a puzzle Berger expects will occupy researchers for a while.

The team is also clear about what the signal is not. It is not evidence of extraterrestrial intelligence. Berger acknowledged that radio signals are commonly associated with the search for alien life, while stressing that this radio signal is "something very different": the fingerprint of a magnetic field churning out auroras on a world where no one expects to find life.

If the result survives peer review, astronomers will gain a new, direct tool for measuring exoplanet magnetic fields and a way to test theories about how planets are built. Longer term, the same method could be aimed at smaller worlds, where a magnetic field might indicate the kind of atmospheric protection that keeps habitability possible. A radio signal has reached Earth from Beta Pictoris b, and for the first time, the planet it came from is known. More space and science stories are updated on the Science topic page.