Shimmering lights danced as far south as Jamaica ... And, after two-plus weeks hidden on the back side of the sun, that same colossal sunspot group is about to point toward Earth once again.

"Sunspots are complex magnetic regions of the sun where energy can be stored in huge amounts," astronomer Peter T. Gallagher said.

Last month, the strongest geomagnetic storm in decades brought the northern lights to Washington State. The storm was set off by coronal mass ejections released by a sunspot cluster. Since it ...