| A | B |
|---|
| Geocentric | a description of the solar system in which all of the planets revolve around Earth (p.51) |
| Heliocentric | a description of the solar system in which all of the planets revolve around the sun (p.52) |
| Ellipse | an elongated circle |
| Inertia | the tendency of a moving object to continue in a straight line or a stationary object to remain in place (p.53) |
| Nuclear fusion | the process by which hydrogen atoms join together to form helium |
| Core | the central part of the sun |
| Photosphere | the inner layer of the suns atmosphere (p.57) |
| Chromosphere | the middle layer of the suns atmosphere (p.57) |
| Corona | the outer layer of the suns atmosphere (p.57) |
| Solar wind | a stream of electrically charged particles produced by the suns corona (p.58) |
| Sunspot | a dark area of gas on the sun that is cooler than surrounding gases (p.58) |
| Prominence | a loop of gas that protrudes from the suns surface |
| Solar flare | an explosion of hydrogen gas from the suns surface that occurs when loops in sunspot regions suddenly connect (p.60) |
| Terrestrial planets | the name given to the four inner planets |
| Retrograde rotation | the spinning motion of a planet from east to west |
| Greenhouse effect | the trapping of heat by a planets atmosphere (p.66) |
| Gas giant | the name given to the first four outer planets: Jupiter |
| Comet | a ball of ice and dust whose orbit is a long |
| Asteroids | objects revolving around the sun that are too small and too numerous to be considered planets (p.82) |
| Asteroid belt | the region of the solar system between the orbits of Mars and Jupiter |
| Meteoroid | a chunk of rock or dust in space (p.83) |
| Meteor | a streak of light in the sky produced by the burning of a meteoroid in Earths atmosphere (p.83) |
| Meteorite | a meteoroid that has hit Earths surface (p.83) |
| Extraterrestrial life | life that arises outside of Earth (p.84) |
