A Simple Guide to the Solar System and Its Eight Planets

Meet the eight planets, understand their order from the Sun, and learn how rocky worlds differ from giant planets.

Our Solar System is built around the Sun and includes eight major planets, dwarf planets, moons, asteroids, comets and countless smaller objects. The eight planets, moving outward from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

8 planetsMercury through Neptune.

4 rocky worldsMercury, Venus, Earth and Mars.

2 gas giantsJupiter and Saturn.

2 ice giantsUranus and Neptune.

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 planets formed from a disk of gas and dust around the young Sun more than 4.5 billion years ago.

The eight planets in order from the Sun

The order is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The first four are relatively small, dense and rocky. The four outer planets are much larger and contain far more gases and volatile materials.

NASA illustration showing planets of the Solar System — NASA/JPL illustration of Solar System worlds. Planet spacing in such diagrams is compressed so all major worlds can be shown together.

The four inner rocky planets

Mercury, Venus, Earth and Mars have solid surfaces and are often called terrestrial planets. Mercury is the smallest and closest to the Sun. Venus has a dense carbon-dioxide atmosphere and extreme surface heat. Earth has liquid oceans and a life-supporting atmosphere, while Mars is a cold desert with evidence that liquid water shaped its ancient surface.

The giant planets

Jupiter and Saturn are gas giants dominated by hydrogen and helium. Uranus and Neptune are called ice giants because their interiors contain larger proportions of water-, methane- and ammonia-rich materials. All four have rings and extensive moon systems.

Hubble views of Jupiter Saturn Uranus and Neptune — Hubble views of the four giant planets: Jupiter, Saturn, Uranus and Neptune. Credit: NASA/ESA/Hubble.

Why every planet is different

Distance from the Sun matters, but it is only part of the story. Planet size, composition, atmosphere, internal heat, collisions and geological history all helped create very different worlds from the same original protoplanetary disk.

Beyond Neptune

Beyond Neptune lies the Kuiper Belt, home to many icy bodies including Pluto and other dwarf planets. Even farther away, the distant Oort Cloud is thought to be a vast reservoir of icy objects that can become long-period comets.

A system still being explored

Robotic missions continue to study planets, moons, rings and small bodies. Exploring our own Solar System gives astronomers a local laboratory for understanding planetary systems around other stars.

Simple takeaway: The Solar System has four small rocky inner planets followed by four giant outer planets, all orbiting the Sun in the same planetary family.

FAQ

What are the eight planets in order?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Why is Pluto not one of the eight planets?

Pluto is classified as a dwarf planet under the modern astronomical definition because it has not cleared its orbital neighborhood.

Which planet is the largest?

Jupiter is the largest planet in the Solar System.