Atomic line shapes in stellar spectra

International audienceThe spectrum emitted by a star is determined by the conditions where the photons last scatter in its atmosphere . It carries a signature of the presence of atomic species, and of the effects of atomic collisions and motions on the radiative process. To the astronomer interested in the star, these spectra offer clues to its composition, temperature, surface gravity, magnetic field, rotation and line-of-sight motion. To the atomic physicist, stellar spectra are a probe for collision processes under conditions that are difficult to reproduce in a laboratory. Indeed, an understanding of the underpinning line shape physics is key to exploring a wide range of interesting astronomical phenomena-answering questions about the color and composition of brown dwarfs, the temperature, size and age of white dwarfs, and the detection of extrasolar planets and their atmospheres