Twin NASA spacecraft have observed a huge explosion of plasma on the surface of the sun, the first time such a coronal mass ejection has been monitored in 3-D.

These ejections can knock out satellites and power grids if they head towards Earth, as well as triggering the pretty Northern and Southern Lights.

NASA’s two Solar TErrestrial RElations Observatory (Stereo) craft are in orbit around the Sun, with one ahead and one behind our planet. Their data should help scientists predict when coronal mass ejections will hit us, and how worried we should be.

“Before this unique mission, measurements and the subsequent data of a CME observed near the sun had to wait until the ejections arrived at Earth three to seven days later,” says Angelos Vourlidas, of the Naval Research Laboratory in Washington (press release). “Now we can see a CME from the time it leaves the solar surface until it reaches Earth, and we can reconstruct the event in 3D directly from the images.”

The BBC focuses on what all this might mean for Earthlings, in particular for those concerned with satellites. Chris Davis, of mission partner the Rutherford Appleton Laboratory in the UK, says a forthcoming paper will describe an ejection for which a warning could have been given a full day before.

“That’s ample time to power down a satellite until the worst of the storm has passed; and if you’re an astronaut on the space station, you would have had plenty of time to get into an area that has much better shielding,” he says.

Vic Pizzo, of National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colorado, told National Geographic, “We always knew if you had two views, you could do a vastly better job [predicting CME impacts]. And that’s what they’re getting here.”

Image: artist’s impression of one of the Stereo craft imaging a coronal mass ejection / Walt Feimer, NASA’s Goddard Spaceflight Center