| A | B |
|---|
| star | glowing ball of hot gas that makes its own energy and light |
| planet | large object in space that orbits a star such as the sun |
| moon | natural satellite that orbits a planet |
| solar system | a star, such as the sun, and all the objects that revolve around it in space |
| fusion | process by which particles combine to form a new particle |
| galaxy | group of billions of stars |
| atmosphere | envelope of gas surrounding an object in space |
| sunspot | dark area on the sun's surface that gives off less energy than the rest of the sun |
| inner planets | Mercury, Venus, Earth, Mars |
| outer planets | Jupiter, Saturn, Uranus, Neptune |
