Study Notes for Chapter 30:

1. Study Notes forChapter 30: Stars, Galaxies, and the Universe

2. Chapter 30 Section 1: Characteristics of Stars

3. 1 • By analyzing the light that a star emits, astronomers can determine the __________ and __________ of a star. composition temperature

4. 2 • Scientists determine the composition and temperature of stars by analyzing the ______ of the light that stars emit. spectra

5. 3 coolest red • The _______ stars are ____ in color, the hottest stars are _____. blue

6. 4 appear • Stars _______ to move in the sky because ______ is moving. Earth

7. 5 • A star moving away from the Earth has a spectrum that is shifted toward ______. red

8. 6 light • A light-year is the distance _____ travels in a year.

9. 7 6,000 • About ______ stars are visible from Earth without a telescope.

10. 8 • ________ magnitude is the brightness of a star as it appears from Earth. Apparent

11. 9 Absolute • ________ magnitude is the true brightness of a star.

12. Chapter 30 Section 2: Stellar Evolution

13. 10 • After its temperature rises to 10,000,000°C, a _________ becomes a star when nuclear fusion begins. protostar

14. 11 • During the main sequence stage, ________ fuses into _______ to generate energy in a star’s core. hydrogen helium

15. 12 • A star with the sun’s mass would stay on the _____ sequence of the H-R diagram for about 10 billion years. main

16. 13 • A large, bright star whose hot core has used most of its hydrogen is a _____. giant

17. 14 • A small, hot, extremely dense core left after a star collapses is a _____ dwarf. white

18. 15 • A white ______ is a hot, extremely dense core of matter left after a star _________. dwarf collapses

19. 16 • Many astronomers believe that black _______ do not exist. dwarfs

20. Chapter 30 Section 3: Star Groups

21. 17 • A galaxy is made of stars, dust, and gas bound together by _______. gravity

22. Chapter 30 Section 4: The Big Bang Theory

23. 18 red • Hubble’s discovery that there was ____ shift in the spectra of galaxies lead to an understanding that the universe is _________. expanding

24. 19 • Red shift in the spectra of galaxies told ________ that the universe is expanding. Hubble

25. 20 14 • The ____ bang occurred about ___ billion years ago. big

26. 21 • Astronomers believe that cosmic background ________ formed shortly after the big bang. radiation

27. 22 dark • Most of the universe is made of _____ energy and dark _______. matter

28. THE END