  Coronal mass ejections (CMEs) are huge expulsions of magnetized matter from
the Sun and stars, traversing space with speeds of millions of kilometers per
hour. Solar CMEs can cause severe space weather disturbances and consumer power
outages on Earth, whereas stellar CMEs may even pose a hazard to the
habitability of exoplanets. While CMEs ejected by our Sun can be directly
imaged by white-light coronagraphs, for stars this is not possible. So far,
only a few candidates for stellar CME detections are reported. Here we
demonstrate a different approach, based on sudden dimmings in the
extreme-ultraviolet (EUV) and X-ray emission caused by the CME mass loss. We
report dimming detections associated with flares on cool stars, indicative of
stellar CMEs and benchmarked by Sun-as-a-star EUV measurements. This study
paves the way for comprehensive detections and characterizations of CMEs on
stars, important for planetary habitability and stellar evolution.
