| A | B |
|---|
| geocentric | a description of the solar system with the earth at the center |
| heliocentric | a desciption of the solar system in which all of the planets revolve around the sun |
| ellipse | an oval shape, the shape of the planets' orbits |
| nuclear fusion | the process in which smaller nuclei combine into larger nuclei forming heavier elements and releasing energy |
| core | the central part, in the sun it is where nuclear fusion takes place |
| photosphere | the inner layer of the sun's atmosphere, the part you see with your eyes |
| chromoshpere | the middle layer of the sun's atmosphere |
| corona | the outer layer of the sun's atmosphere, the solar wind comes from here |
| solar wind | a stream of charged particles from the sun that cause the auroras (northern and southern lights) |
| terrestrial planets | the name given to the four planets closest to the sun |
| gas giant | the name given to Jupiter, Saturn, Neptune, and Uranus |
| comet | a ball of ice and dust that revolves around the sun |
| asteroid | objects revolving around the sun that are too small to be called planets |
| asteriod belt | the region of the solar system between the orbits of Mars and Jupiter where many asteroids are found |
| meteoroid | a chunk of rock or dust in space |
| meteorite | a meteoroid that has hit the Earth's surface |
| diameter | distance from one side of a circle to another going through the middle |
| mass | how much matter (stuff) is in an object, not how big or weight |
| gravity | the force that pulls objects toward each other, partly determined by the mass of an object |
| density | measurement of how much mass is in a certain amount of volume (space) |
| temperature | a measurement of how fast the molecules in a substance are moving. |
