Astronomy Assignment Stellar Nomenclature II
Your Name______________________________________
This assignment is due on Thursday , July 23
Submit this cover sheet with your assignment.
Review Questions from Chapter 11 in Astronomy Notes
1. How is spectroscopy used to find the composition of stars?
2. Two stars have proper motions of 0.5 arc seconds/year. Star (A) is 20 parsecs away and star (B) is 30
parsecs away. Which one is moving faster in space?
3. How the masses of stars found? What kind of star systems are used and which famous law of orbital
motion is used?
4. How many times closer to the center of mass is the massive star than the low-mass star?
5. Star A is 0.2 A.U. from the center of mass and its companion star B is 0.6 A.U. from the center of mass.
Which star is more massive?
6. What special type of binary star system is used to find the diameters of stars?
7. The white dwarf Sirius B has a temperature of 14,000 K and a luminosity only 0.00794 times the Sun's
luminosity. What is the diameter of Sirius B in kilometers? (The Sun's radius = 696,000 kilometers.)
8. Why do very hot stars have no hydrogen lines?
9. Why do very cool stars have no hydrogen lines?
10. What is the grouping of stars by spectral type based on?
11. What are the 7 basic spectral types in order of temperature (hottest to coldest)?
12. If our Sun has a surface temperature of 5840 K, how many times hotter than the Sun is the hottest Otype star? How many times cooler than the Sun is the coolest M-type star?
13. What fraction of the stars are main sequence stars?
14. What is the range of temperatures found on the surface of main sequence stars?
15. What is the range of luminosities produced by main sequence stars? Compare them to the Sun (Watts
are ridiculously small energy units to use).
16. What is the range of diameters for main sequence stars? Compare them to the Sun (miles and kilometers
are ridiculously small length units to use). Red giants, supergiants, white dwarfs are not main sequence
stars.
17. What is the trend in the stellar diameters vs. temperature for main sequence stars? (As temperature
increases, the diameter _________.)
18. What is the trend in the stellar luminosities vs. temperature for main sequence stars? (As temperature
increases, the luminosity _________.)