HW#23: pg. 442-443 Rev 4 – 6; CST 4 – 6
Rev 4 – 6
4. How do astronomers measure stellar temperatures?
5. Briefly describe how stars are classified according to their spectral characteristics.
6. Describe how astronomers measure stellar radii. List some characteristics of red-giant and white-dwarf stars.
CST 4 – 6
4. Compared with a star of absolute magnitude –2 at a distance of 100 pc, a star of absolute magnitude 5 at a distance of 10 pc will appear (a) brighter; (b) fainter; (c) to have the same brightness; (d) bluer.
5. Pluto's apparent magnitude is approximately 14. According to Figure 17.7 ("Apparent Magnitude"), Pluto can be seen (a) with the naked eye on a dark night; (b) using binoculars; (c) using a 1-m telescope; (d) only with the Hubble Space Telescope.
6. Stars of spectral class M do not show strong lines of hydrogen in their spectra because (a) they contain very little hydrogen; (b) their surfaces are so cool that most hydrogen is in the ground state; (c) their surfaces are so cool that most hydrogen is ionized; (d) the hydrogen lines are swamped by even stronger lines of other elements.