National Aeronautics and Space Administration

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Solar ejections (actually called Coronal Mass Ejections or CMEs) are the most powerful drivers of the Sun-Earth connection. Yet despite their importance, scientists don't fully understand the origin and evolution of CMEs, nor their structure or extent in interplanetary space.

Coronal mass ejections (CMEs), are powerful eruptions that can blow up to 10 billion tons of the Sun's atmosphere into interplanetary space. They can trigger severe magnetic storms when they collide with Earth's magnetosphere, and can damage and even destroy satellites,or cause electrical power outages.

STEREO (Solar TErrestrial RElations Observatory) is the third mission in NASA's Solar Terrestrial Probes program (STP). This two-year mission provides a unique and revolutionary view of the Sun-Earth System. The two nearly identical observatories - one ahead of Earth in its orbit, the other trailing behind – traces the flow of energy and matter from the Sun to Earth as well as reveals the 3D structure of coronal mass ejections and help us understand why they happen. STEREO also provides alerts for Earth-directed solar ejections, from its unique side-viewing perspective adding it to the fleet of Space Weather detection satellites.

Learn about STEREO's twin satellites that were launched to collect data about the sun. Find out why we study the sun and what scientists learn from these missions.