The star Beta Pictoris b, photographed by the European Southern Observatory, is home to the gas giant discovered in 2008 — Photo: European Southern Observatory/AP Photo/picture alliance
Since the early 1990s, we have known that there are planets that orbit stars outside the Solar System – so-called exoplanets. Since then, radio telescopes have scoured the sky in search of emissions coming from these distant worlds, without being able to distinguish the voice of a planet from that of its star. This silence, finally, seems to have been broken.
An international team led by Kevin Ortiz Ceballos of the Harvard-Smithsonian Center for Astrophysics has presented what it describes as the first detection of radio emissions attributed directly to an exoplanet. This is Beta Pictoris b (β Pictoris b), a gas giant discovered in 2008 and located just over 63 light years from Earth.
A radio signal, not an alien message
Before the excitement about possible extraterrestrial contact takes over, it's worth clarifying: that's not what this is about. The signal is not related to a civilization trying to communicate, but rather to auroras, the same phenomenon that lights up Earth's polar skies and also generates Jupiter's radio bursts.
Everything indicates that something similar happens in β Pictoris b, although under the influence of an extraordinarily intense magnetic field. It would channel energetic particles into the upper layers of the atmosphere, where their interaction could give rise to auroral emissions like those detected by radio telescopes.
MeerKAT captures radioauroras from another world
The discovery is based on observations carried out by the MeerKAT radio telescope array, in South Africa, during four distinct sessions between 2025 and 2026. In them, astronomers detected a persistent emission, in addition to brief bursts that were repeated. They had a strong circular polarization, that is, the radio waves rotated in a spiral as they propagated. This pattern is common in emissions produced by auroras and, therefore, indicated that the signal probably had this origin.
Behind these emissions would be the so-called electron cyclotron maser instability (ECMI), a mechanism already known to astronomers for explaining the radioauroras of planets in the Solar System, such as Jupiter.
However, the usual problem remained: how do we know if the signal is born on the planet or on the star that houses it? The key was in quasars, extremely distant objects that served researchers as a reference to improve measurements.
According to the Phys.org portal, thanks to them it was possible to locate the emissions with enough precision to identify β Pictoris b as their origin and rule out both its star and the neighboring planet β Pictoris c, as the ZME Science website also details.
But identifying the origin was just the beginning: radio waves also offered a way to measure the intensity of the planet's magnetic field, functioning as a true magnetometer at a distance.
From Carnarvon, South Africa, MeerKAT's antennas used distant quasars as a reference to identify the exact origin of the signal — Photo: Wang Lei/Xinhua/IMAGO
How to measure the magnetic field of a distant planet?
In this type of auroral emission, the maximum frequency of radio waves is related to the intensity of the magnetic field that produces them: the higher this limit, the stronger the field must be. In β Pictoris b, radio telescopes recorded signals up to 3.5 gigahertz, the upper end of the range observed by MeerKAT.
Based on these signals, the researchers calculated that the magnetic field in the region where the emissions originate reaches an intensity much higher than that of Jupiter and around 2,500 times greater than that recorded on the Earth's surface. This is, however, a minimum value: the field can be even more intense.
According to the authors of the study, available on the arXiv platform, this is the first time that the intensity of an exoplanet's magnetic field has been directly measured.
Why were the signals detected this time?
Astronomers had been trying to capture these emissions for years, but previous searches had yielded no results.
In 2022, a campaign with the Very Large Array radio telescope ended without detections, and in 2024, another attempt focused on β Pictoris b itself also found no signals. There was, however, an important difference: while this last study investigated frequencies between 250 and 500 megahertz, the new observations with MeerKAT covered a higher range, from 0.85 to 3.5 gigahertz, according to the study.
Furthermore, the planet has characteristics that make it an especially interesting target. With a mass between 10 and 12 times that of Jupiter and an extraordinarily intense magnetic field, it completes a rotation around itself in just eight or nine hours. This rapid rotation could contribute to fueling their auroral emissions. The apparent separation from the star also allowed researchers to pinpoint the origin of the signals.
According to ZME Science, the researchers also considered other possible energy sources, such as stellar wind or interaction with a hypothetical moon, similar to that between Jupiter and its moon. The calculations, however, showed that none of these mechanisms, alone, would provide enough energy to explain the signal strength.
A new window into exoplanets
The result, not yet peer-reviewed, opens a new avenue for studying the magnetism of exoplanets, a property that until now has not been measured directly on these worlds.
Knowing the intensity of the magnetic field of these planets can also offer clues about their possible habitability. It depends, in part, on how a planet's atmosphere responds to the wind from its star and to what extent it manages to preserve itself in the face of these effects.
The team is now directing its efforts to seven other gas giants in five nearby star systems. The expectation is that the next generation of radio telescopes, which will be between five and seven times more sensitive, will allow us to detect signals on these planets similar to those observed in β Pictoris b.
