Astronomers have utilized the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile and the Gemini North telescope to measure wind speeds on seven ultra-hot Jupiters. On these worlds, which are scorched by their nearby stars and tidally locked, winds reach extreme velocities ranging from approximately 7,200 km/h to over 25,000 km/h.
The study, published on June 2, 2026, in the journal Nature Astronomy, was led by Julia Seidel of the Laboratoire Lagrange (Observatoire de la Côte d’Azur, France). The research team includes members from various institutions, including partners involved with the ESPRESSO instrument on the VLT and MAROON-X on Gemini North.
Key Observations
Scientists observed how wind speeds vary according to the planet's temperature during their investigation. The hotter the planet, the slower the winds—a finding that contradicts purely hydrodynamic models, which suggest that higher temperatures should accelerate atmospheric circulation. This behavior is best explained by the presence of planetary magnetic fields, which generate "magnetic drag" by interacting with ionized gas in the atmosphere.
According to the ESO, this represents the first robust measurement of magnetism on planets beyond our Solar System. The magnetic fields of these hot giants are estimated to be comparable to those in our own Solar System—measuring several times stronger than Saturn's or roughly half the strength of Jupiter's. This marks the first reliable indirect measurement of exoplanet magnetic field strength derived from atmospheric dynamics.
About WASP-76b and Previous Data
WASP-76b is a classic example of an ultra-hot Jupiter. Previously, studies in 2022 and other years used iron spectroscopy to measure wind speeds of 5.9–9.8 km/s (roughly 21,000–35,000 km/h) in various regions of its atmosphere and terminator. The new research places this data in the broader context of seven planets and links these anomalies to magnetic drag.
The observations were conducted using the high-precision ESPRESSO spectrograph at the VLT in Chile's Atacama Desert. The official ESO press release (eso2606) was issued on June 2, 2026.
Significance of the Discovery
This discovery necessitates a revision of atmospheric circulation models for hot Jupiters, which must now incorporate the influence of magnetic drag. It represents a vital step toward understanding how magnetic fields affect atmospheric evolution, water retention, and the potential habitability of planets.
Future observations with ESPRESSO, and eventually with the ESO’s Extremely Large Telescope (ELT), will allow for the refinement of magnetic field parameters on other exoplanets.
