What is a nebula?
A nebula is a giant cloud of gas and dust in space. Some nebulas are places where new stars are born, while others are the remains of dying or exploded stars.
The word nebula comes from Latin for mist or cloud. Nebulas are mostly made of hydrogen and helium with small amounts of dust. Gravity can pull dense parts of these clouds together until they become hot enough for nuclear fusion to start, creating new stars. That is why many nebulas are called stellar nurseries.
Nebulas come in different types. Emission nebulas glow in bright colors because nearby young stars heat their gas. Reflection nebulas shine by reflecting starlight off dust. Dark nebulas block light from objects behind them. Planetary nebulas are shells of gas thrown off by dying stars like the Sun, and supernova remnants are left by exploded stars.
Famous examples
The Orion Nebula, about 1,300 light-years away, is visible to the naked eye as a fuzzy patch in Orion's sword. The Eagle Nebula contains the Pillars of Creation, towering columns of gas photographed by Hubble in 1995 and again by the James Webb Space Telescope in 2022.
Did You Know?
Planetary nebulas have nothing to do with planets. Early astronomers named them that because they looked like round, planet-like disks through small telescopes.