Solar system

2. The name given to the first four outer planets: Jupiter, Saturn, Uranus, and Neptune.
3. The central part of the sun, where nuclear fusion occurs.
7. A meteoroid that has hit Earth's surface.
10. 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.
11. A ball of ice and dust whose orbit is a long, narrow ellipse.
12. The outer layer of the sun's atmosphere.
14. FUSION The combining of two atomic nuclei into a single larger nucleus, as when two hydrogen atoms join together to form helium, releasing energy.
15. The inner layer of the sun's atmosphere.
17. An elongated circle, or oval shape; the shape of the planets' orbits.
18. Objects revolving around the sun that are too small and too numerous to be considered planets.

1. The region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found.
4. LIFE Life that arises outside of Earth.
5. A chunk of rock or dust in space.
6. A description of the solar system in which all of the planets revolve around the sun.
8. The tendency of a moving object to continue in a straight line or a stationary object to remain in place.
9. The middle layer of the sun's atmosphere.
13. A description of the solar system in which all of the planets and the sun revolve around the Earth.
16. A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere.