A nebula is a giant cloud of dust and gas floating in space. These cosmic clouds can stretch for millions of miles, glowing with brilliant colors: deep reds, electric blues, and vibrant greens. Some look like wispy smoke, others like towering pillars or spiraling whirlpools.

Nebulae (the plural of nebula) are stellar nurseries where new stars are born. Gravity slowly pulls the gas and dust together over millions of years until it becomes so dense and hot that a star ignites, bursting into nuclear fusion. Our own sun formed inside a nebula about 4.6 billion years ago.

Other nebulae form when massive stars explode at the end of their lives, scattering their material across space in spectacular displays. These remnants eventually help create new nebulae, new stars, and even new planets. The iron in your blood and the calcium in your bones came from ancient stellar explosions.

Before telescopes became powerful enough to see clearly into space, astronomers called anything that looked fuzzy or cloudy a nebula. Today we know that some of those fuzzy patches are actually distant galaxies, but true nebulae remain among the most beautiful sights in the universe.