Chapter 18 Inner and Outer Planets
universe All of space and everything in it
galaxy A system of dust, gas, and many millions of stars held together by gravity
astronomy The study of the Sun, Moon, stars, and other objects in space
solar system Includes the Sun, the planets, their moons, and other objects
craters Dents shaped like bowls that are made when meteorites crash into a surface
space probe A vehicle that carries cameras and other tools for studying different objects in space
satellite An object that orbits another object in space