For the first time, astronomers have been able to pinpoint the source of radio waves emanating directly from a planet outside the solar system, and not from its star, in a result that opens a new window for studying distant worlds.
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The signal came from the giant planet Beta Pictoris b, located about 63 light-years away, orbiting the star Beta Pictoris. Thanks to this signal, scientists were able to directly estimate the strength of its magnetic field for the first time on a planet outside our solar system.
Beta Pictoris b is not an unknown world to scientists; its discovery was announced in 2008 after a faint point was observed near its star by the Very Large Telescope of the European Southern Observatory, and subsequent observations confirmed that it is a planet orbiting the star.
It is a gas giant with a mass about nine times that of Jupiter, orbiting at a distance of approximately 10 astronomical units, roughly the same distance as Saturn from the Sun. Its day is also remarkably short, taking only about eight hours to complete one rotation.
Radio waves bearing the signature of twilight
The team used the MeerKAT radio array in South Africa and observed the system on four occasions during 2025 and 2026. Signals with frequencies ranging from 0.85 to 3.5 GHz appeared as fast, repetitive flashes, along with continuous radio emission, and the waves were strongly circularly polarized.
These properties are consistent with radio waves associated with the aurora borealis, a phenomenon we also know about on Earth when charged particles interact with a magnetic field.
But the biggest challenge was determining whether the waves were actually emanating from the planet or from the nearby bright star. To resolve this, the researchers compared the radio source's location with precise reference positions of stars and found that it matched the position of Beta Pictoris b, not the star.
Furthermore, the study found that the signal's characteristics themselves are inconsistent with known mechanisms that could produce this type of emission from the host star. The researchers wrote, "There is no known physical mechanism causing radio emissions in stars of this type that can explain the observed emission."
First direct measurement of the magnetic field of an exoplanet
The significance of the signal lies not only in its confirmation that the planet emits radio waves, but also in the information it provides about its magnetic field. Researchers have identified the radiation as originating from a process known as the electron cyclotron maser, a mechanism that produces radio waves when electrons move through a magnetic environment.
Since the highest radiation frequency is directly related to the strength of the magnetic field in the region where it originated, the team was able to estimate the field strength of the planet to be at least 1250 gauss. This is the first direct measurement of the magnetic field strength of an exoplanet.
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