Cape Canaveral, Fla. ? Twin spacecraft blasted off Wednesday night on a mission to study huge eruptions from the sun that can damage satellites, disrupt electrical and communications systems on Earth and endanger spacewalking astronauts.

The two spacecraft, known as STEREO, for Solar Terrestrial Relations Observatory, lifted off from Cape Canaveral, stacked one on top of the other aboard a single Delta II rocket.

Scientists hope the $550 million, two-year mission will help them understand why these eruptions occur, how they form and what path they take.

The eruptions – called solar flares – typically blow a billion tons of the sun’s atmosphere into space at a speed of 1 million mph. The phenomenon is responsible for the Northern Lights, or aurora borealis, the luminous display of lights seen in the upper latitudes of the Northern Hemisphere.

NASA hopes information about the solar flares will help astronauts who fly to the moon and eventually Mars in the coming decades. Astronauts exposed to the eruptions can receive a year’s worth of radiation.