2025/11/12 by Tianqi Cang, P. Petit, Cang, Tianqi +25 · 1 voice
Physics and Astronomy · #Astronomy and Astrophysical Research #Scientific Research and Discoveries #Stellar, planetary, and galactic studies
paper · pdf · doi:10.1038/s41467-025-66624-9
openalex created_date 2025/11/19 · openalex publication_date 2025/11/29 · openalex updated_date 2026/08/04
Magnetic fields in the upper atmospheres of solar-like stars are believed to provide an enormous amount of energy to power the hot coronae and drive large-scale eruptions that could impact the habitability of planetary systems around these stars. However, these magnetic fields have never been routinely measured on stars beyond the solar system. Through decade-long spectropolarimetric observations, we have now achieved the measurements of magnetic fields in the lower and middle chromospheres of three M-dwarfs. Our results indicate that the line-of-sight component of the chromospheric magnetic fields can reach up to hundreds of Gauss, whose sign frequently opposes that of the photospheric field. The measurements highlight the magnetic field complexity and the variation with height close to the surface of these M-dwarfs. They provide critical constraints on the energy budget responsible for heating and eruptions of stellar upper atmospheres, and enable assessments of how stellar magnetic activity may affect exoplanet environments. Magnetic fields in stellar upper atmospheres are key to understanding stellar activity and its planetary effects. Here, the authors study chromospheric magnetic fields in three M-dwarf stars using spectropolarimetric observations, finding fields reaching hundreds of Gauss with complex height-dependent structures.