The origin and role of magnetic fields in the evolution of stars is arguably the last major unsolved problem of stellar physics. Astronomers agree that magnetism plays a central role at many stages of stellar life, from the formation of stars and planetary systems to supernovae explosions and winds of dying stars. Magnetic activity of the Sun is clearly observed as 11-year sunspot cycle that affects the entire solar system.
Despite an abundance of indirect evidence of the importance of magnetic fields, direct detection and study of magnetic fields on stars other than the Sun is an extremely challenging task. Such an analysis was impossible until recently, leading astronomers to speculate about stellar magnetism based on theoretical models extrapolated from the Sun using indirect proxy indicators (flaring, X-ray emission).