| A | B |
|---|
| ASTEROID BELT | The region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found. |
| ASTEROIDS | Objects revolving around the sun that are too small and too numerous to be considered planets. |
| CHROMOSPHERE | The middle layer of the sun's atmosphere. |
| COMET | A ball of ice and dust whose orbit is a long, narrow ellipse. |
| CORE | The central part of the sun, where nuclear fusion occurs. |
| CORONA | The outer layer of the sun's atmosphere. |
| ELLIPSE | An elongated circle, or oval shape; the shape of the planets' orbits. |
| EXTRATERRESTRIAL LIFE | Life that arises outside of Earth. |
| GAS GIANTS | The name given to the first four outer planets: Jupiter, Saturn, Uranus, and Neptune. |
| GEOCENTRIC | A description of the solar system in which all of the planets and the sun revolve around the Earth. |
| GREENHOUSE EFFECT | The process by which heat is trapped in the atmosphere by water vapor, carbon dioxide, methane, and other gases that form a "blanket" around Earth. |
| HELIOCENTRIC | A description of the solar system in which all of the planets revolve around the sun. |
| INERTIA | The tendency of a moving object to continue in a straight line or a stationary object to remain in place. |
| METEORITE | A meteoroid that has hit Earth's surface. |
| METEOR | A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere. |
| METEOROID | A chunk of rock or dust in space. |
| NUCLEAR FUSION | The combining of two atomic nuclei into a single larger nucleus, as when two hydrogen atoms join together to form helium, releasing energy. |
| PHOTOSPHERE | The inner layer of the sun's atmosphere. |
| PROMINENCE | A loop of gas that protrudes from the sun's surface, linking parts of sunspot regions. |
| RETROGRADE ROTATION | The spinning motion of a planet from east to west, opposite to the direction of rotation of most planets and moons. |
| SOLAR FLARE | An explosion of hydrogen gas from the sun's surface that occurs when loops in sunspot regions suddenly connect. |
| SOLAR WIND | A stream of electrically charged particles produced by the sun's corona. |
| SUNSPOT | Dark, cooler regions on the surface of the sun. |
| TERRESTRIAL PLANETS | The name given to the four inner planets: Mercury, Venus, Earth, and Mars. |
