The sunspot that triggered the massive solar storm that lit up Earth's skies with auroras in May returned. <br />Now called AR3723 (originally AR3664, then AR3697). It blasted a M9-class solar flare end of last month.<br /><br />Credit: NASA / SDO and the AIA, EVE, and HMI science teams / HelioViewer - edited by: Steve Spaleta
