Explore how scientists trace the journey of material exploding from the sun.
Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and X-rays produced in a solar flare—which travels at the speed of light and can reach Earth in eight minutes—coronal mass ejections, or CMEs, are giant, expanding clouds of solar material that take one to three days to reach our planet. When a CME blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun so that the much fainter material in the solar atmosphere—including CMEs—can be seen in the surrounding space. NASA's STEREO mission consists of two spacecraft, each equipped with two coronagraphs (COR 1, COR 2) and an extreme ultraviolet camera (EUV) that together help scientists model the journey of a CME from the sun's surface into its atmosphere and beyond. Watch the video for views of an eruption seen by the STEREO Ahead spacecraft.