Page 323 - NS-2 Textbook

318 NAUTICAL SCIENCES

4. Why is communication with distant galaxies imprac- 17. How are star clusters classified?
tical at the present time? 18. A. Wllat is a galaxy?
5. A. How are stars classified? B. To which galaxy does our solar system belong?
B. What are the principal star colors? 19. What is the shape of the Milky Way?
6. What is the difference between apparent and absolute 20. What is the difference between the two population
magnitude of stars? groupings in our galaxy?
7. A. What is the "main sequence" of stars? 21. A. How are galaxies classified?
B. What is the spectrum-luminosity diagram? B. What are the three classifications?
8. What is unique about white dwarf stars?
9. What are cepheid stars?
10. What is believed to be the sequence in the life cycle
Vocabulary
of a star?
11. What is the principal factor determining what kind light-year nova
of star vdll be "born"? luminosity nebula
12. Why do brighter stars have shorter lives? apparent magnitude supernova
13. What is thought to be the normal evolution of stars? absolute magnitude binaries
14. ·What are novae? cepheid variable galaxy
15. A. What is a nebula? main sequence star Milky Way
B. What are the three kinds of nebulae? constellation spiral galaxy
16. What are binaries? black hole ellipsoidal galaxy