"This breakthrough opens a completely new window on exoplanet research. It's the first time we can compare the magnetic environments of other worlds."
– Julia Seidel
Magnetic Fields Measured on Seven Ultra-Hot Jupiters
A study published in Nature Astronomy reports the first-ever measurements of magnetic field strengths on exoplanets, achieved by analyzing their extreme wind speeds. The research, led by Julia Seidel of Laboratoire Lagrange, Observatoire de la Côte d'Azur, France, utilized data from the MAROON-X instrument on the Gemini North telescope and the ESPRESSO instrument on ESO’s VLT.
The team measured wind speeds on seven gas giant exoplanets that are tidally locked to their host stars. This locking creates extreme temperature differences between the permanent day and night sides.
A Counterintuitive Discovery
The data revealed a surprising pattern:
- Wind speeds ranged from about 7,200 km/h to over 25,000 km/h.
- Hotter planets actually had slower winds.
Researchers attribute this counterintuitive finding to magnetic fields acting as a brake on charged particles. The inferred magnetic field strengths are comparable to those in the Solar System: approximately four times stronger than Saturn's field or about half the strength of Jupiter's.
Implications for Habitability
- Earth’s magnetic field protects its atmosphere from cosmic radiation.
- Understanding exoplanet magnetic fields may help assess their habitability.
“The hotter the planet, the slower the wind. This is totally counterintuitive... Something must happen that slows down the wind speeds for hotter objects.”
– Vivien Parmentier