Download Chapter 13 (Properties of Stars)

Chapter 13
The Stars as Suns
1. Which of the following properties of stars does NOT require knowledge of the earth-star distance
to find it out?
A. Mass.
B. Luminosity.
C. Density.
D. Surface temperature.
2. The color of a star is MOST DIRECTLY related to its:
A. mass.
B. surface temperature.
C. central (core) temperature.
D. luminosity.
3. Assuming that stars radiate like blackbodies, you must know which of the following properties in
order to infer the radius of a star?
A. Luminosity and surface temperature.
B. Luminosity and distance.
C. Luminosity and flux.
D. Luminosity and mass.
4. You are observing two stars with the SAME luminosity. Star A is 5 light years from the earth;
star B is 50 light years. What result do you expect of their fluxes?
A. Flux from A will be 10 times greater than B.
B. Flux from B will be 10 times greater than A.
C. Flux from A will be 100 times greater than B.
D. Flux from B will be 100 times greater than A.
5. A measurement of a star's flux tells us directly the:
A. star's distance from the earth.
B. star's total energy output compared to the sun's.
C. star's surface temperature.
D. rate at which energy reaches the earth.
6. If the sun were twice as far away as it is now, we would receive:
A. twice as much flux.
B. the same amount of flux.
C. half as much flux.
D. one-fourth as much flux.
7. When heliocentric parallax is measured, a SMALL parallax means that the star is:
A. relatively far away.
B. relatively close by.
C. not very bright
D. small in radius.
8. The more massive a main sequence star is, then the:
A. redder it is.
B. more luminous it is.
C. more time it spends on the main sequence.
D. greater percentage of heavy elements it contains.
9. Which of the following is NOT needed in order to determine the individual masses of stars in a
binary system?
A. Orbital period.
B. Location of the center of mass.
C. Distance to the binary system.
D. Colors of each of the stars.
10. Consider two main-sequence stars that have different masses. You can correctly infer that the
more massive star will have a:
A. lower luminosity and shorter lifetime.
B. higher luminosity and shorter lifetime.
C. higher luminosity and longer lifetime.
D. lower luminosity and longer lifetime.
11. Observational evidence that stars have regions of magnetic activity like active regions on the
sun is that of:
A. colors of different sun-like stars.
B. emission lines in the spectra of unusual stars.
C. flares in a wide range of the electromagnetic spectrum.
D. very strong solar winds from sun-like stars.
12. Consider observing the spectra from a binary star system whose orbits are in the line of sight
(edge-on). The maximum red shift, tells you that the:
A. less massive star is moving across the line of sight.
B. more massive star is moving across the line of sight
C. less massive star is moving away from us.
D. less massive star is moving toward us.
13. On the H-R diagram: What are the correct units for the vertical axis?
A. Temperature/wavelength.
B. Luminosity/brightness.
C. Temperature/Color.
D. Luminosity/wavelength.
14. Refer to the H-R diagram: What are the units of the horizontal axis?
A. Luminosity/brightness.
B. Color/luminosity.
C. Wavelength/temperature increasing to the right.
D. Wavelength/temperature decreasing to the right.
15. Refer to the H-R diagram: for stars in general, a higher mass star may be found:
A. at higher luminosity and lower temperature.
B. at higher luminosity and higher temperature.
C. observed at shorter wavelength and lower luminosity.
D. at lower luminosity and lower temperature.
16. The brightness magnitude scale for stars is arbitrary with:
A. decreasing number associated with increased luminosity.
B. decreasing number associated with increased wavelength.
C. increasing number associated with increased luminosity.
D. increasing number associated with increased wavelength.
17. The song written by Jane Taylor has the lyrics "Twinkle, twinkle little star, How I wonder what
you are." Why is it that when we view stars with our naked eye, they seem to twinkle?
A. The effect is caused by Earth's atmospheric changes.
B. Rapid motion of sunspots causes it
C. It depends on the orientation of the Earth's magnetosphere.
D. Because most stars are members of a binary system.
18. Which of the following methods can NOT be used to determine the distance to stars?
A. Stellar parallax.
B. Bouncing radar waves off the surface.
C. Measure flux and temperature, use extrapolated luminosity from the H-R diagram.
D. Measure the motion of a moving cluster of stars and triangulate their distance.
19. Betelgeuse is a _______ star in the ________ constellation.
A. white dwarf/Orion
B. red supergiant/Orion
C. red supergiant/Leo
D. black hole,Leo
20. Were the sun 3x as far away as it is now, we would receive:
A. 2 times as much flux.
B. the same amount of flux.
C. 1/2 as much flux.
D. 1/9 as much flux.
21. Were the sun l0x as far away as it is now, we would receive:
A. 2 times as much flux.
B. the same amount of flux.
C. 1/10 as much flux.
D. 1/100 as much flux.
22. When heliocentric parallax is measured, a LARGE parallax means that the star is:
A. relatively far away.
B. small in radius.
C. relatively close by.
D. not very bright.
23. On the H-R diagram for stars in general, a lower mass star may be found:
A. at higher luminosity and lower temperature.
B. at higher luminosity and higher temperature.
C. at lower luminosity and lower temperature.
D. observed at shorter wavelength and higher luminosity.
24.-32. Match the letter of the stars to their position on the H-R diagram.
A. upper left B. upper right
C. lower left
D. lower right
24. The largest known stars.
25. Most low mass, red stars in our neighborhood.
26. Sirius B, the hot white dwarf only 1/1000th as luminous as the sun.
27. The vast majority of bright blue naked eye stars.
28. Most naked eye stars that appear red or orange in color.
29. The most massive young stars.
30. The least massive young stars.
31. Stars about as large as the planet earth.
32. Red giants like Antares and Betelguese.
ESSAYS
1. In photos taken a year apart, you notice a faint star that has moved much more than any other in
that period. How long will it take you to find its distance, and how will you do it?
2. Explain why that the vast majority of naked eye stars lie to the upper left of the Sun on the H-R
diagram, yet the majority of nearby stars are found to the lower right of our star. Relate this to the
limitations of human vision.
3. Sirius and its companion are almost the same temperature, yet Sirius is about 10,000x brighter
than its companion. Explain why they differ so much in luminosity.
4. Explain why we presently do not have sufficient information about the distances to some of the
brightest stars in the galaxy (such as Betelguese and Rigel), yet know with great precision the
distances to some of the least luminous stars. How will the corrected optics of the Hubble Space
Telescope help change this odd situation?
5. How can the spectrum tell us if we are observing a huge red giant hundreds of light years distant,
or a red dwarf only a few light years distant, if both have the same composition and spectral type
and temperature? Which would be class I? Class V?