The Sun’s Atmosphere is Hotter Than Its Surface

The Sun’s surface is about 5,500°C (9,900°F), but its outer atmosphere—the corona—blazes at over a million degrees. That seems counterintuitive. Normally, things get cooler as you move away from a heat source, but the Sun does the opposite. Scientists think the answer lies in magnetic fields snapping and reconnecting, releasing bursts of energy that superheat the corona. It’s like a campfire where the air above the flames is hotter than the fire itself—a mystery we’re still trying to solve. The Layers cutaway in the 3D model of the Sun labels the photosphere, chromosphere and corona so you can see the order.