Without stellar winds, life as we know it would not exist. Critical chemical elements like carbon are produced inside luminous cool giant stars, transported to the surface by turbulent gas flows, and ejected into interstellar space by massive outflows of gas and dust. Proof for this scenario comes from dust grains that were produced in stellar winds, and detected in meteorites due to their special composition. The current knowledge of stellar winds, however, is incomplete, and does not allow us to fully understand their effects on the evolution of stars, and how they enrich their surroundings with newly produced elements and cosmic dust.
Project EXWINGS aims at a breakthrough in understanding the winds of cool giant and supergiant stars. We will produce a new type of models: global dynamical star-and-wind-in-a-box simulations. For the first time, it will be possible to follow the flow of matter, in full 3D geometry, all the way from the turbulent, pulsating interior of a cool giant, through its atmosphere and dust formation zone in to the region where the wind is accelerated. Extending our unique approach to the warmer, more luminous red supergiant stars, we will explore which mechanisms drive their still enigmatic winds.
Astronomical instruments with high spatial resolution, which give images of the stellar atmospheres where the winds originate, allow us to test the new models. The results of project EXWINGS will contribute to understanding stellar and galactic chemical evolution, and tracing the origin of building blocks for terrestrial planets.