Strange winds reveal strongest hints yet of magnetic activity in exoplanets | ESO
A team of astronomers has found the strongest evidence yet that planets outside our Solar System may be magnetic. Using the European Southern Observatory’s Very Large Telescope (ESO's VLT) and the Gemini North telescope, the researchers measured wind speeds on seven very hot, Jupiter-like exoplanets. The observations revealed that the winds on these planets are most likely governed by magnetic fields, providing the first robust measurement of magnetism on planets outside the Solar System.
“This breakthrough opens a completely new window on exoplanet research. It’s the first time we can compare the magnetic environments of other worlds—a key step toward ultimately understanding which planets can stay alive, keep their water, and perhaps even, one day, host life as we know it,” says Julia Seidel, an astronomer at the Laboratoire Lagrange, Observatoire de la Côte d’Azur, France and lead author of the study published today in Nature Astronomy.
Earth’s magnetic field influences our atmosphere in complex ways, and is therefore a key factor in understanding what keeps the planet habitable for life. Magnetic fields are also present in other Solar System planets, like Jupiter and Saturn. However, for the past 15 years, no one succeeded in directly measuring the strength of the magnetic fields of exoplanets—until now.
The team, however, did not set out to measure magnetic fields but, rather, winds. They measured wind speeds on seven exoplanets orbiting different stars: gas giants like Jupiter, but each tidally locked to its host star and very close to it. Just as we always see only one side of the Moon, these planets always keep one face towards the star, resulting in a scorching hot day side and a freezing cold night side. This temperature difference creates a climate completely distinct from the one on our planet with extremely strong winds. The wind speeds in their sample ranged from around 7200 km/h to over 25 000 km/h; in comparison, the fastest winds measured on Jupiter reach speeds of around 1500 km/h.
“In the beginning we set out to check if the atmospheric winds behaved the same way for all hot planets,” explains Seidel, previously an astronomer at ESO in Chile. For their measurements, the team used data from the ESPRESSO instrument on ESO’s VLT, in the Chilean Atacama Desert, and from a similar instrument on the Gemini North telescope in Hawaiʻi, USA. (The VLT is an ESO telescope while Gemini North is one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.)
However, when they looked at how the wind speeds varied with planet temperature, they saw a very intriguing pattern emerge: the hotter the planet, the slower the wind. “This is totally counter intuitive because, all things being equal, hot planets have more energy to accelerate the winds! Something must happen that slows down the wind speeds for hotter objects,” says study co-author Vivien Parmentier, a professor at the Laboratoire Lagrange.
The team concluded that the most consistent explanation for this mystery is the presence of planet-wide magnetic fields, since these fields can work as a brake, slowing down the motion of charged particles in the atmosphere. The data therefore allowed the researchers to infer the strength of the magnetic field in each of the studied planets. They found them to be comparable in strength to those found in our Solar System: approximately four times as strong as Saturn's or about half the strength of Jupiter's.
Such strong magnetic fields could affect more than just the wind on these distant planets. "Here on Earth, we know the beauty of the northern and southern lights, where particles from the Sun hit our magnetic field and are guided toward the poles, colliding with gases in the atmosphere to produce colorful displays of green, pink, and purple," explains study co-author Bibiana Prinoth, a former PhD student at Lund University, Sweden, now an astronomer at ESO in Garching, Germany. On the studied exoplanets, the magnetically driven aurorae could be even more dramatic. The team eagerly anticipates the arrival of ESO’s Extremely Large Telescope, which will help to characterize not only large, Jupiter-like exoplanets but also smaller ones like Earth, possibly even detecting gases that could produce aurorae on these distant worlds. Prinoth says: “I like to imagine that some of these worlds have a sky filled not only with stars, but with vast curtains of colorful light dancing across a planet that’s half in perpetual day and half in endless night.”
This research was presented in a paper to appear in Nature Astronomy (doi:10.1038/s41550-026-02870-1).
Credit: European Southern Observatory (ESO)
Directed by: Angelos Tsaousis, Martin Wallner
Editing: Angelos Tsaousis
Written by: Margarida Lopes
Footage and photos: ESO, Luis Calçada, Martin Kornmesser, Gianluca Lombardi, Mahdi Zamani, Stefan Ströbele, NASA, ESA, J. Nichols (University of Leicester), and G. Bacon (STScI)
Acknowledgment: A. Simon (NASA/GSFC) and the OPAL team
Duration: 1 min, 24 seconds
Release Date June 2, 2026
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