An April 2010 VLT image showing Beta Pictoris b located 6.5 AU from its star. (Image Credit: ESO)
A gas giant called Beta Pictoris b, located about 63 light-years from Earth, has been emitting strongly circularly polarized bursts. Astronomers recently detected the emissions using MeerKAT, a 64-dish radio telescope array in South Africa. According to the team, this is the first time radio signals were traced to an individual exoplanet rather than a host star. The method could enable scientists to measure the magnetic fields of planets beyond our solar system.
This is a key discovery as it’s difficult to directly measure planetary magnetic fields. They may affect a planet’s interaction with stellar winds and how a planet’s atmosphere is protected from energetic particles. Even Earth has this same effect, as the magnetic field shields the atmosphere from the solar wind.
Beta Pictoris b’s radio signals are created by a mechanism related to planetary auroras. Charged particles interacting with a planet’s magnetic field and atmosphere can produce radio waves through electron cyclotron maser instability (ECMI). Other planets, like Jupiter, in our Solar System produce similar radio emissions.
Between 2025 and 2026, MeerKAT observed Beta Pictoris b four times. It detected radio signals ranging from 0.85 to 3.5 GHz. According to the paper, the signals had rapidly varying bursts that were strongly circularly polarized. This is consistent with coherent auroral radio emissions.
Most importantly, the team determined that the radio signals came from the exoplanet and not the star or another planet in the system. Since the host star is magnetically quiet, it was easier to separate Beta Pictoris b’s faint radio emission from stellar activity. The highest radio frequency also provided researchers with data about the planet’s magnetic environment. Based on the researchers’ understanding of the signal as ECMI, 3.5 GHz suggests there is a 1.25 kilogauss magnetic field where those radio waves were produced.
The approach could pave the way toward investigating magnetism on planets outside this Solar System. In such cases, astronomers use those radio observations to analyze giant exoplanets’ magnetic environments and get better insight into how planets interact with host stars.
This can also contribute to the search for potentially habitable planets. Magnetic fields are capable of preserving a planet’s atmosphere if it gets hit with stellar activity. That makes it a key factor when determining if a distant planet provides ideal conditions for life.
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