The Sun unleashed a series of four coronal mass ejections (CMEs) on May 22-24, 2010 as the STEREO Ahead spacecraft watched the action. In the coronagraph images, the Sun, blocked out by an occulting disk (seen as red), is represented by a white disk to show its relative size. CMEs are large solar storms that expel a billion tons of matter at a million miles per hour or more. Credit: NASA/European Space Agency