Coronal mass ejections (CMEs) are huge expulsions of magnetized matter from the Sun and stars, traversing space with speeds of millions of kilometres 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. Although 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 have been reported. Here we demonstrate a different approach that is based on sudden dimmings in the extreme ultraviolet 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 which are benchmarked by Sun-as-a-star extreme ultraviolet measurements. This study paves the way for comprehensive detections and characterizations of CMEs on stars, which are important factors in planetary habitability and stellar evolution.

日冕物质抛射 (CME) 是磁化物质从太阳和恒星中的巨大喷射，以每小时数百万公里的速度穿越太空。太阳 CME 会导致地球上严重的空间天气干扰和消费者断电，而恒星 CME 甚至可能对系外行星的可居住性构成威胁。虽然太阳喷射出的 CME 可以通过白光日冕仪直接成像，但对于恒星来说这是不可能的。到目前为止，仅报告了少数恒星 CME 探测的候选者。在这里，我们展示了一种不同的方法，该方法基于由 CME 质量损失引起的极紫外和 X 射线发射的突然变暗。我们报告了与冷星耀斑相关的变暗检测，表明恒星 CME，并以太阳作为恒星的极紫外测量为基准。