Thanks to our dynamic core, Earth is wrapped in a magnetic sheath that protects the planet from harmful cosmic radiation. Called the magnetosphere, this sheath is normally invisible to human eyes—except near the planet’s poles, where shimmering, eerie lights in the nighttime skies betray its presence.

Called auroras, these dancing lights intensify when the sun hurls a particularly large volley of charged particles at Earth, which then collide with atoms in the planet’s atmosphere and produce a dazzling array of colors. (Here's how Canadian photographers discovered a whole new type of aurora.)

An aurora’s colors depend on what kind of atom cosmic particles smash into. Collide with an oxygen atom at high altitude, and it produces a red color,