Solar System

The solar system is the Sun and all the objects held to it by gravity.

What is in the solar system

The solar system includes:

The Sun is at the center, and its gravity helps hold the solar system together.

Simple solar system overview diagram showing the Sun in the center with planets, moons, asteroids, comets, and dwarf planets labeled around it

The Sun

The Sun is a star.

It gives Earth:

The Sun is by far the largest object in the solar system. Everything else moves around it.

The planets

The eight planets in our solar system are:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune

The planets vary a lot in size, composition, and distance from the Sun. Some are rocky worlds with solid surfaces, while others are giant planets with deep atmospheres.

Lineup diagram of the eight planets in order from the Sun, with each planet labeled by name

Inner and outer planets

The planets are often grouped into two sets.

Inner planets

The inner planets are:

These are the rocky planets.

They are also much closer to the Sun than the outer planets.

Rough average distances from the Sun:

Outer planets

The outer planets are:

These planets are much larger overall, and they orbit much farther from the Sun.

Rough average distances from the Sun:

There is also a large distance gap after Mars:

So even the nearest outer planet is about 342 million miles farther from the Sun than the farthest inner planet.

Comparison diagram grouping the inner rocky planets on one side and the larger outer planets on the other

Moons

A moon is a natural object that orbits a planet.

Here are the current moon counts for the planets:

Moons vary widely. Some are rocky, some are icy, and some may even have oceans beneath an outer layer of ice.

Scientists sometimes discover and confirm new moons, so these numbers can change over time.

Asteroids, comets, and dwarf planets

Not everything in the solar system is a planet.

Asteroids

Asteroids are mostly rocky objects. Many are found in the asteroid belt, a broad region between Mars and Jupiter.

Comets

Comets are made mostly of ice, dust, and rock. When they move close to the Sun, heat can cause some of their material to stream away and form a glowing tail.

Dwarf planets

Dwarf planets orbit the Sun and are round, but they are not classified as full planets.

Examples include:

Small object diagram showing an asteroid, a comet with a tail, and a dwarf planet, each labeled with a short note about what makes it different

Orbits

An orbit is the path an object follows as it moves around another object in space.

Examples:

An orbit is the result of forward motion and gravity working together.

Orbit diagram showing Earth traveling around the Sun and the Moon traveling around Earth with curved path arrows

Gravity

Gravity is the force that pulls masses toward one another.

In the solar system, gravity:

Gravity is the main reason the solar system stays organized.

Gravity diagram showing arrows pulling planets toward the Sun and a moon toward a planet

The solar system is huge

The solar system is extremely large.

That is why many pictures of space are not drawn to scale.

What is a light-year?

A light-year is a unit of distance, not time.

It means the distance light travels in one year:

Light-years are usually used for distances between stars and between larger structures in space.

Inside our solar system, light-year values are extremely small, so miles are usually easier to picture.

Not-to-scale comparison diagram showing how tiny the planets are compared with the Sun and how far apart they really are

A simple way to picture it

One simple way to picture the solar system is as a set of objects organized around one star:

Final takeaway

At the most basic level:

Sources