Astronomy produces far more data than scientists can immediately analyze. Much of it is stored, catalogued, and rarely revisited. A new study shows that some of the most valuable discoveries may already be sitting in those archives. 

By reprocessing radio telescope observations collected years ago, researchers have identified short-lived radio signals from nearby stars and, in some cases, from systems known to host exoplanets. 

Some of these signals are consistent with magnetic interactions between stars and their planets—an effect long predicted by theory but rarely observed directly. The work offers a new way to study magnetic fields beyond the solar system, a property that plays a major role in how planets develop and whether they can remain stable over time.

Why conventional radio astronomy missed these signals

Radio telescopes such as LOFAR observe wide sections of the sky in a single pointing. Every observation contains signals from many stars simultaneously, but traditional analysis methods reduce this information to static images. 

This approach is effective for mapping distant cosmic structures, but it removes most of the information about how radio emission varies on short timescales.

The key limitation was practicality. Monitoring rapid radio variability from hundreds of stars individually would require dedicated observations lasting far longer than a human career. As a result, radio astronomers rarely attempted to track fast-changing stellar or planetary signals across large datasets.

The research team addressed this problem by developing Multiplexed Interferometric Radio Spectroscopy (RIMS). Instead of compressing observations into still images, RIMS preserves time-dependent information and separates radio signals by direction. This allows scientists to follow changes in radio emission from many stars simultaneously, second by second, within a single observation.

To test the method, the team applied RIMS to more than 1.4 years of data from LOFAR’s LoTSS sky survey. From this archive alone, they extracted approximately 200,000 time-resolved radio spectra from nearby stars and star–planet systems. 

“RIMS exploits every second of observation, in hundreds of directions across the sky. What we used to do source by source, we can now do simultaneously. Without this method, it would have taken nearly 180 years of targeted observations to reach the same detection level,” Cyril Tasse, first study author and a researcher at the Paris Observatory, said.

The reprocessed data revealed intense radio bursts associated with extreme stellar activity, similar in nature to large solar eruptions. Also, some bursts showed strong circular polarization, a signal characteristic of magnetic processes. 

Several of these events match theoretical expectations for electromagnetic interactions between a star and a close-orbiting planet, although stellar activity alone cannot yet be ruled out. One notable example comes from the system GJ 687.

“Our results indicate that some of the radio bursts, most notably from the exoplanetary system GJ 687, are consistent with a close-in planet disturbing the stellar magnetic field and driving intense radio emission,” Jake Turner, one of the study authors, said. 

“Specifically, our modeling shows that these radio bursts allow us to place limits on the magnetic field of the Neptune-sized planet GJ 687 b, offering a rare indirect way to study magnetic fields on worlds beyond our solar system,” Turner added.

Time to confirm the origin

Magnetic fields influence how planets lose atmospheres, interact with stellar radiation, and evolve over long periods. Earth’s magnetic field, for example, plays a role in protecting the planet from charged particles emitted by the Sun. 

However, despite their importance, magnetic fields have been almost impossible to measure for exoplanets. This study demonstrates that low-frequency radio data can offer an indirect solution. By identifying radio emissions produced through magnetic interactions, RIMS provides a practical way to study planetary magnetism across many systems at once. 

The method has already been tested on another instrument, the French NenuFAR telescope, where it detected a burst that could represent only the second reported case of radio emission linked to an exoplanet.

However, confirmation is essential. Stars themselves can generate strong radio bursts, and separating planetary effects from stellar activity requires follow-up observations. 

Therefore, “we are now pursuing targeted follow-up observations to confirm the planetary origin of both signals. A confirmed detection would provide a powerful new way to probe an exoplanet’s magnetic field,” Turner said.

The study is published in the journal Nature Astronomy.