What are stars like giant lightbulbs?

Stars are giant balls of hot gas that glow because they are constantly smashing tiny pieces together deep inside them, just like a lightbulb shines when electricity heats its wire.

Imagine your bedroom lightbulb. When you flip the switch, electricity rushes through a thin tungsten wire, making it so hot that it glows bright yellow. Stars do something similar on a much grander scale. Instead of electricity, stars use nuclear fusion. This is when tiny particles called hydrogen atoms crash into each other and fuse to become helium.

Every time two hydrogen atoms merge, they release a burst of energy as heat and light. You can feel this same kind of heat if you stand close to a campfire or hold your hand near a hot oven. A star is essentially a massive fusion reactor that never runs out of fuel for billions of years. It glows steadily because the pressure from its own weight keeps squeezing the center, forcing those atoms to keep smashing together without stopping.

While a lightbulb fits in your palm, the Sun, a typical star, is about 109 times wider than Earth. If Earth were a small blueberry, the Sun would be a huge watermelon! Even though stars are much larger and hotter than household bulbs, the basic idea is the same: hot matter releases light.

Lightbulbs rely on humans to plug them in, but stars have their own power source. They shine because of the intense heat created by their internal atomic collisions. So when you look up at night and see a star twinkling, you are looking at a distant sun that is doing exactly what your bedside lamp does, just with way more fuel and much higher temperatures.