Astronomers have traced repeating radio emissions directly to an exoplanet outside the solar system for the first time, identifying the source as Beta Pictoris b, a gas giant located about 63 light-years from Earth. Researchers from the Harvard & Smithsonian Center for Astrophysics and the University of Oregon used South Africa’s MeerKAT radio telescope array to distinguish the signals from the planet’s parent star, Beta Pictoris.
The finding provides a new way to study the magnetic environment of distant planets. The research has been made available on arXiv but has not yet been published in a peer-reviewed journal.
Beta Pictoris b was discovered in 2008 and has a mass estimated at 11.729 times that of Jupiter, according to NASA data cited in the study. The planet takes about 23.6 years to orbit its A-type star and is located approximately 10.018 astronomical units from it.
MeerKAT isolates radio bursts from Beta Pictoris b
Radio activity had previously been detected from the Beta Pictoris system, but astronomers could not determine whether the emissions originated from the star or from a planet orbiting it.
To resolve the source, researchers repeatedly observed the system with MeerKAT, a highly sensitive radio telescope array. The observations allowed them to identify brief, recurring radio bursts that appeared at the position of Beta Pictoris b rather than at the location of its host star.
The researchers reported rapidly repeating, strongly circularly polarised bursts alongside persistent radio emission across frequencies ranging from 0.85 to 3.5 GHz.
The result is significant because radio emissions from planets within the solar system are already known, but the researchers said a radio signal had not previously been unambiguously localised to an exoplanet rather than its host star.
Powerful auroras appear to be behind the repeated emissions
The radio bursts are not evidence that an extraterrestrial civilisation is attempting to communicate with Earth. Instead, researchers attribute the emissions to auroral activity generated by the planet’s magnetic field.
The process is broadly comparable to the auroras seen on Earth, although the activity on Beta Pictoris b occurs on a much larger scale. High-energy particles travelling through space can be guided along magnetic field lines towards the planet. When electrons reach the upper atmosphere, they produce intense radio emissions.
The planet’s rapid rotation is another important part of the process. Beta Pictoris b completes a rotation in roughly eight to nine hours. According to the researchers, this fast spin can generate strong electrical currents, helping produce the recurring radio bursts detected by MeerKAT.
Beta Pictoris b may have an unusually strong magnetic field
Analysis of the radio emissions also points towards a powerful magnetic environment around the exoplanet. Researchers estimate that Beta Pictoris b could have a magnetic field roughly 2,500 times stronger than Earth's.
The measurement offers scientists an opportunity to study properties that are otherwise difficult to observe directly on a planet located outside our solar system. Magnetic fields influence how planetary atmospheres interact with charged particles and can also provide clues about the internal processes taking place inside a planet.
The researchers said their measurements are consistent with predictions based on dynamo scaling for a young, massive gas giant.
Why the radio discovery matters for exoplanet research
The study could expand the methods available to astronomers for investigating exoplanets. Many distant worlds are detected through their effects on stars, such as changes in brightness or the movement of the star caused by the planet's gravity. Directly identifying radio emissions associated with a planet can provide a different type of information about its physical environment.
The researchers described the observation as the first direct measurement of magnetic field strength for an exoplanet. Their work also suggests that auroral radio emissions could become a useful tool for studying the magnetic fields of other worlds beyond the solar system.
For Beta Pictoris b, the observations connect its rapid rotation, auroral activity and strong magnetic field with the radio emissions detected from Earth. The study therefore offers a new window into the behaviour of a young gas giant far beyond the solar system, although the findings remain subject to further scientific review and publication.
