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Magnetic Fields Detected on Hot Jupiters, Slowing Winds

6/2/2026

Summary

Seidel Detects Magnetism

French astronomers led by Julia Seidel reported the first detection of magnetic fields on exoplanets.
They measured winds on seven ultra-hot Jupiters with the VLT in Chile and Gemini North, finding speeds of 4,470–15,530 mph.
Hotter planets showed slower winds, suggesting magnetic fields brake atmospheric flow.
The magnetic fields are about four times Saturn’s and half Jupiter’s.
The study appeared in Nature Astronomy on June 2 2026.

Summary

Researchers Probe Magnetism

Researchers used helium 1083 nm spectropolarimetry to directly probe exoplanet magnetic fields.
Early-ingress UV signatures in WASP-12b transits have been used to infer magnetic field strength.
Scaling-law studies link a planet’s internal heat flux to magnetic field intensity, citing Christensen 2009 and Yadav & Thorngren 2017.
Evolutionary models (Kilmetis et al. 2024) predict hot-Jupiter fields evolve over gigayears and that convection suppression in inflated planets (Elias-López et al. 2025) may alter field generation.

History

Historical Context

Mayor and Queloz’s 1995 detection of 51 Pegasi b inaugurated the exoplanet era, proving hot Jupiters could orbit Sun-like stars. Subsequent work on HD 209458 b revealed atmospheric dynamics, including a superstorm reported in 2007. Building on those spectroscopic milestones, Julia Seidel’s team now measures magnetic fields on seven ultra-hot Jupiters, extending the quest to probe planetary interiors.

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Seidel Detects Magnetism

French astronomers led by Julia Seidel reported the first detection of magnetic fields on exoplanets.
They measured winds on seven ultra-hot Jupiters with the VLT in Chile and Gemini North, finding speeds of 4,470–15,530 mph.
Hotter planets showed slower winds, suggesting magnetic fields brake atmospheric flow.
The magnetic fields are about four times Saturn’s and half Jupiter’s.
The study appeared in Nature Astronomy on June 2 2026.

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