Stars are generally too far away to allow a direct study of their surfaces, even using the largest telescopes available on Earth. Yet, from the example of the Sun, we know that characterising dynamic surface behaviour (such as spot formation, emergence and evolution of magnetic fields) is critical for understanding the physics of stars and their impact on circumstellar environment, including planetary systems. It turns out that by studying profiles of the absorption lines visible in stellar spectra it is possible to detect spots and magnetic fields. Moreover, by applying a mathematical procedure of regularised inversion one can reconstruct two-dimensional scalar or vector maps of stellar surfaces with a spatial resolution by far exceeding direct imaging capabilities of world’s largest telescopes. In this seminar I outline the basic principles and present examples of the application of this powerful astrophysical remote sensing method.
