Meet the eight planets, understand their order from the Sun, and learn how rocky worlds differ from giant planets.
The Solar System begins with the Sun
The Sun contains almost all of the Solar System's mass. Its gravity keeps planets, dwarf planets, asteroids, comets, and smaller objects in orbit.
The four inner rocky planets
Mercury, Venus, Earth, and Mars are relatively small worlds with solid surfaces. They differ greatly in atmosphere, temperature, geology, and history despite forming in the same inner region.
The giant planets
Jupiter and Saturn are gas giants dominated by hydrogen and helium. Uranus and Neptune are often called ice giants because their interiors contain larger proportions of water, methane, and ammonia-rich material.
Why every planet is different
Distance from the Sun matters, but composition, size, atmosphere, internal heat, and collisions also shaped each planet. The Solar System is a collection of very different outcomes from the same original disk of gas and dust.
Beyond Neptune
The region beyond Neptune contains dwarf planets and many icy objects. Farther still, comets may originate from distant reservoirs that preserve material from the Solar System's formation.
A system still being explored
Robotic missions continue to reveal new details about planets, moons, rings, and small bodies. Studying the Solar System also gives astronomers a local reference for understanding planetary systems around other stars.
Continue with our related Neela Asman guide. For broader science background, visit NASA Science.