Sometimes, the Sun throws off huge amounts of matter. These events are called coronal mass ejections, or CMEs. A CME can release up to 20 billion tons of this material. If that material were rock, it would make a mountain roughly 2.75 miles across and almost one-half mile high!  The ejected material can travel a million or more miles per hour (500 km/second). Solar flares and CMEs are the biggest, most violent "explosions" in our solar system, releasing the power of around one billion hydrogen bombs!

Fast CMEs occur more often near the peak of the 11-year solar cycle, and can trigger major disturbances in Earth's magnetosphere. The Sun can eject matter in any direction, so only some of the CMEs will actually encounter Earth.  When Earth is in the path of a CME, we get "space weather." The one nice effect is Northern Lights and Southern Lights around the magnetic poles. They occur when the charged solar particles follow the Earth's magnetic lines of force right down into the atmosphere at the poles. The particles cause gases in the air to glow and shimmy like colorful, dancing draperies of light.  But space weather can also cause a lot of damage to our technologies. Electrical power systems on the ground can be damaged. Astronauts in the International Space Station can be injured. Jets flying over the poles can expose passengers and crews to significant doses of radiation. Earth-orbiting satellites can be disabled.