The northern lights, known scientifically as the aurora borealis, are one of nature's most spectacular displays. Shimmering curtains of green, pink, and violet light ripple across the night sky in the far north, with a matching display, the aurora australis, gracing the far south.

Auroras are created by the Sun. Our star constantly streams out charged particles, and when these reach Earth they are funneled by the planet's magnetic field toward the polar regions. There they collide with gas atoms high in the atmosphere, and those collisions release energy as light, in much the same way that electricity makes a neon sign glow.

An astronaut's view of the aurora from orbit, glowing in a ring around the pole.
An astronaut's view of the aurora from orbit, glowing in a ring around the pole.

Because the charged particles follow Earth's magnetic field lines down toward the poles, auroras form in oval shaped bands around the magnetic north and south. Seen from space, these glowing rings encircle the top and bottom of the planet, brightening and shifting as the stream of particles from the Sun rises and falls.

The color of an aurora depends on which gas is struck and at what altitude. Oxygen produces the familiar green glow, and at greater heights a rarer, deep red. Nitrogen adds blues and purples to the display.

The aurora over Sweden, glowing green from oxygen high in the atmosphere.
The aurora over Sweden, glowing green from oxygen high in the atmosphere.

The most vivid auroras follow powerful bursts of activity on the Sun, which is why they grow more frequent and intense during the peak of the Sun's roughly eleven year cycle of activity. A single large solar storm can supercharge the lights and push them far beyond their usual range.

The lights are best seen near the Arctic Circle, in places such as Iceland, northern Scandinavia, Canada, and Alaska, on clear, dark winter nights well away from city lights. During especially strong solar storms, they can occasionally be seen much farther from the poles than usual.

The aurora photographed over Alaska, a prime viewing location near the Arctic Circle.
The aurora photographed over Alaska, a prime viewing location near the Arctic Circle.

For centuries, people across the northern world explained the lights with myth and legend, seeing in them spirits, omens, or the glow of distant fires. Only in modern times did science reveal their true cause in the interaction of the Sun and the Earth's magnetic field. Understanding them has taken nothing away from their power to inspire wonder.