Stars! Stars! Stars! (3 page)

A planet is a large object that orbits a sun but doesn’t make its own light. Planets reflect the light from stars. They don’t twinkle because they are closer to Earth than stars are.

Gravity is the force that keeps objects in orbit. Gravity keeps us from floating off the Earth!

A moon orbits a planet the way a planet orbits a sun. Some planets, such as Saturn, have many moons.

An asteroid is a rocky object, much smaller than a planet, that orbits a sun.

A comet is made of ice and dust and orbits a sun.

A meteor is a space rock that crashes into the surface of a planet or moon.

A shooting star isn’t a star at all. It’s a meteor that burns up when it gets close to Earth.

A solar system is all of the planets, moons, asteroids, comets and other matter that orbits a sun.

A galaxy is made up of billions of stars, gas and dust held together by gravity. Planet Earth is in the Milky Way Galaxy.

The universe is all of the light, matter and energy that exists in time and space.