Solar System A group of objects in space that move around a central star

Star A huge, burning sphere of gases; for example, the sun

Planet A large object that moves around a star.

Asteroid A small rocky object that moves around the sun.

Comet A small mass of dust and ice that orbits the sun in a long, oval-shaped path.

Orbit The path that an object such as a planet makes as it revolves around a second object.

Axis An imaginary line that runs through both poles of a planet.

Inner Planet The planets closest to the sun; Mercury, Venus, Earth, and Mars.

Outer Planet The planets farthest from the sun; Jupiter, Saturn, Uranus, Neptune, and Pluto.

Gas Giant The planets Jupiter, Saturn, Uranus, and Neptune; which are large spheres made up mostly of gases.

telescope A device people use to observe distant objects with their eyes.

Space probe A space vehicle that carries cameras, instruments, and other research tools.

constellation The pattern formed by a group of stars in the sky.