| Word | Definition |
| Geocentric | A description of the solar system in which all of the planets revolve around Earth. |
| Heliocentric | A description of the solar system in which all of the planets revolve around the sun. |
| Ellipse | An elongated circle, or oval shape; the shape of the planets' orbits. |
| Inertia | The tendency of a moving object to continue in a straight line or a stationary object to remain in place. |
| Nuclear fusion | The process by which hydrogen atoms join together to form helium, releasing energy. |
| Core | The central part of the sun, where nuclear fusion occurs. |
| Photosphere | The inner layer of the sun's atmosphere. |
| Chromosphere | The middle layer of the sun's atmosphere. |
| Corona | The outer layer of the sun's atmosphere. |
| Solar wind | A stream of electrically charged particles produced by the sun's corona. |
| Sunspot | A dark area of gas on the sun that is cooler than surrounding gases. |
| Prominence | A loop of gas that protrudes from the sun's surface, linking parts of sunspot regions. |
| Solar flare | An explosion of hydrogen gas from the sun's surface that occurs when loops in sunspot regions suddenly connect. |
