Moons

Earth is the only planet that has a single moon. Our Moon is the brightest and most familiar object in the night sky. In many ways, the Moon is responsible for making Earth such a great home. It stabilizes our planet's wobble, which has made the climate less variable over thousands of years.

Earth sometimes temporarily hosts orbiting asteroids or large rocks. They are typically trapped by Earth's gravity for a a few months or years before returning to an orbit around the Sun. Some asteroids will be in a long “dance” with Earth as both orbit the Sun.

Some moons are bits of rock that were captured by a planet's gravity, but our Moon is likely the result of a collision billions of years ago. When Earth was a young planet, a large chunk of rock smashed into it, displacing a portion of Earth's interior. The resulting chunks clumped together and formed our Moon. With a radius of 1,080 miles (1,738 kilometers), the Moon is the fifth largest moon in our solar system (after Ganymede, Titan, Callisto and Io).

The Moon is farther away from Earth than most people realize. The Moon is an average of 238,855 miles (384,400 kilometers) away. That means 30 Earth-sized planets could fit in between Earth and the Moon.