Recently, Professor Fu Jianning’s team from the School of Physics and Astronomy at Beijing Normal University, in collaboration with researchers from Peking University, the University of Toulouse in France, and other domestic and international institutions, has achieved a groundbreaking milestone by measuring the chromospheric magnetic fields of stars beyond the Sun for the first time. Utilizing decade-long high-resolution polarimetric spectroscopic observations, this study reveals the intricate magnetic field structures in stellar upper atmospheres, providing crucial observational evidence for understanding stellar flares and their impacts on exoplanet environments. The research paper, titled Measuring the magnetic fields in the chromospheres of low-mass stars, was published in Nature Communications.

The abstract of the paper is as follows:

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.

Reference: https://www.nature.com/articles/s41467-025-66624-9