Tracking a solar storm, from the sun to the Earth

What happens when a billion tons or more of plasma explodes from the sun at 3 million miles an hour and hit the Earth? Sometimes, not much. Sometimes, a lot.

NASA announced on Thursday that for the first time researchers have seen one of these explosions, known as a coronal mass ejection, from the time it left the surface of the sun to the point where it engulfed the Earth, 93 million miles away. To study the ejection, researchers used NASA's STEREO twin spacecraft; one orbits the sun ahead of the Earth; the other orbits the sun trailing the Earth.

Knowing the ejections' physics can help scientists predict what will happen when the forces hits the Earth, and the STEREO observations can help in understanding that, researchers say. Although usually it's usually greatly dissipated by the time it reaches Earth, the plasma can still damage satellite electronics and, in extreme cases, power grids on the ground.

The video below shows images taken of the coronal mass ejection by the various instruments on the STEREO spacecraft leading the Earth in it's orbit, according to the NASA website. The sun is on the right and the Earth is the small blue dot on the left.