The sky over an unusually wide swath of the northern hemisphere lit up with a brilliant display of color overnight into Monday morning, dazzling people across North America and Europe.
The display was potentially visible as far south as Iowa in the United States, as well as in parts of southern England, scientists said.
The phenomenon, known as the aurora borealis or northern lights, occurs when particles emitted by the sun collide with particles that are already trapped around Earth’s magnetic field, and can often be seen from parts of Iceland, Canada and Alaska.
But on Friday, the sun let off a large burst of energy, said Robert Steenburgh, a space scientist with the Space Weather Prediction Center at the National Oceanic and Atmospheric Administration. (These bursts are also known as coronal mass ejections.)