Solar System Review

2. The wide, outermost layer of a star's atmosphere.
4. The distance light travels in 1 year (two words).
6. The true brightness of an object.
8. A large ball of gas held together by gravity with a core so hot that nuclear fusion occurs.
12. A graph that plots luminosity vs. temperature of stars (2 initials and word).
13. A process that occurs when the nuclei of several atoms combine into one larger nucleus (two words).
16. Where hot gas moves up toward the surface and cooler gas moves deeper into the interior (two words).
17. The apparent surface of a star.
20. Theory that the universe began from one point billions of years ago and has been expanding ever since (3 words).
21. A cloud of gas and dust.
22. An object whose gravity is so great that no light can escape (2 words).

1. A measure of how bright an object appears from Earth (two words).
3. The average distance between Earth and the Sun, about 150 million km (two words).
5. A hot, dense, slowly cooling sphere of carbon (2 words).
7. Matter that emits no light at any wavelength.
9. A shell of cooler hydrogen above a star's core (two words).
10. Huge collections of stars.
11. The orange-red layer above the photosphere.
14. The shift to a different wavelength (2 words).
15. Spreads light into different wavelengths.
18. An enormous explosion that destroys a star.
19. A dense core of neutrons that remains after a supernova (2 words).