A cluster of giant sunspots called region 3664 has been shooting out powerful eruptions, called coronal mass ejections, over the last several days.Right now, at least five of them are on a direct collision course with Earth, shooting through space at 560 miles per second. As a result, the National Oceanic and Atmospheric Administration issued a rare forecast for a "severe" G4 geomagnetic storm to hit Earth this Friday.It's the first G4 forecast NOAA has issued since 2005. But severe geomagnetic... Read this story