Winds of unprecedented intensity, blowing at tens of thousands of kilometers per hour, now provide the strongest evidence ever obtained of magnetic activity on planets beyond our solar system. At the heart of this breakthrough are researchers from the Lagrange Laboratory at the Côte d’Azur Observatory, who authored a study published in the journal *Nature Astronomy*.
A Magnetic Signature Finally Detected
Astronomers now have the strongest evidence to date of the existence of magnetic fields on exoplanets and can even estimate their intensity. Until now, these fundamental properties remained beyond the reach of observation.
Under the direction of Julia Seidel, an astronomer at the Lagrange Laboratory of the Côte d’Azur Observatory, the scientists utilized the capabilities of the European Southern Observatory’s Very Large Telescope as well as those of Gemini North to study seven ultra-hot gas giants, comparable to Jupiter but orbiting very close to their star.
Their approach is indirect but highly effective: measuring the speed of atmospheric winds.
Extreme winds… and an anomaly
These worlds are subject to extreme conditions. In synchronous rotation, they always present the same face to their star: one hemisphere perpetually scorched, the other plunged into a freezing night. This contrast generates winds of unprecedented violence, reaching speeds between 7,200 and over 25,000 km/h—far exceeding the ~1,500 km/h observed on Jupiter.
But an unexpected result has emerged: the hotter the planet, the slower its winds.
As Vivien Parmentier, also a researcher at the Lagrange Laboratory, points out: this behavior defies physical intuition. A hotter planet should, in theory, generate faster winds.
The key role of magnetic fields
The most convincing explanation lies in the influence of planetary magnetic fields. These fields act as a brake on the charged particles in the atmosphere, thereby slowing down the winds.
Thanks to this interaction, the team was able to estimate the strength of these magnetic fields:
they are comparable to those of the giants of the solar system, reaching about four times that of Saturn and nearly half that of Jupiter.
A Decisive Breakthrough for Habitability
Earth’s magnetic field plays a complex role in retaining the atmosphere and thus helps explain the conditions that make the planet habitable.
This discovery therefore opens a new avenue: comparing the magnetic environments of exoplanets, a key criterion for assessing their potential habitability.
Toward Spectacular Extraterrestrial Auroras
The implications extend beyond atmospheric dynamics alone. As Bibiana Prinoth explains, these magnetic fields could generate auroras far more impressive than those observed on Earth.
These phenomena, analogous to the aurora borealis and aurora australis, could illuminate the skies of these distant worlds with vast curtains of light, in environments where day and night are frozen for eternity.
A prospect reinforced by future instruments
The weak magnetic field intensities we infer today remain beyond the reach of current radio telescopes; however, next-generation instruments like SKA-Low could enable direct detection of these fields for the most promising targets.
The upcoming arrival of the Extremely Large Telescope promises to go even further. Its instruments, such as ANDES or PCS, will make it possible to study not only gas giants but also rocky planets comparable to Earth—and perhaps detect the chemical signatures associated with these magnetic phenomena.
With this discovery, the teams at the Côte d’Azur Observatory have established themselves at the forefront of exoplanet astrophysics, revealing a long-elusive yet fundamental parameter: the magnetism of distant worlds.
Publication:
https://www.nature.com/articles/s41550-026-02870-1
Scientific contacts:
Julia Seidel: julia.seidel@oca.eu
Vivien Parmentier: vivien.parmentier@oca.eu
Press contact:
Margaux Arav: margaux.arav@oca.eu