Study Notes for Chapter 30:

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

2. 1 • A galaxy is made of stars, dust, and gas bound together by ______. • gravity

3. 2 • A large, bright star whose hot core has used most of its hydrogen is a _____. • giant

4. 3 • A light-year is the distance ____ travels in a year. • light

5. 4 • A small, hot, extremely dense core left after a star collapses is a _____ dwarf. • white

6. 5 • A star moving away from the Earth has a spectrum that is shifted toward ______. • red

7. 6 • A star with the sun’s mass would stay on the _____ sequence of the H-R diagram for about 10 billion years. • main

8. 7 • A white ______ is a hot, extremely dense core of matter left after a star _______. • dwarf • collapses

9. 8 • About ______ stars are visible from Earth without a telescope. • 6,000

10. 9 • ______ magnitude is the true brightness of a star. • Absolute

11. 10 • After its temperature rises to 10,000,000°C, a _____ becomes a star when nuclear fusion begins. • protostar

12. 11 • _______ magnitude is the brightness of a star as it appears from Earth. • Apparent

13. 12 • Astronomers believe that cosmic background _______ formed shortly after the big bang. • radiation

14. 13 • By analyzing the light that a star emits, astronomers can determine the ______ and ________ of a star. • composition • temperature

15. 14 • During the main sequence stage, ______ fuses into ______ to generate energy in a star’s core. • hydrogen • helium

16. 15 • Hubble’s discovery that there was ____ shift in the spectra of galaxies lead to an understanding that the universe is ____. • red • expanding

17. 16 • Many astronomers believe that black _____ do not exist. • dwarfs

18. 17 • Most of the universe is made of _____ energy and dark _______. • dark • matter

19. 18 • Red shift in the spectra of galaxies told ______ that the universe is expanding. • Hubble

20. 19 • Scientists determine the composition and temperature of stars by analyzing the ________ of the light that stars emit. • spectra

21. 20 • Stars _____ to move in the sky because ______ is moving. • appear • Earth

22. 21 • The ____ bang occurred about __ billion years ago. • big • 14

23. 22 • The ____ stars are ____ in color, the hottest stars are _____. • coolest • red • blue

24. THE END