Binary and Variable Stars

1. Stellar diameters may be determined from studies of

a. visual binary stars

b. astrometric binary stars

c. spectroscopic binary stars

d. eclipsing binary stars.*

2. In a binary system, the more massive star

a. is at the center of mass.

b. is farthest from the center of mass.

c. is nearest the center of mass. *

d. follows the largest orbit.

e. shows a larger Doppler shift in its spectral lines.

3. What is the absolute magnitude of an RR Lyrae star with an 18-hour period?

a. -1 magnitude.

b. 0.3 magnitude.

c. 0.6 magnitude.*

d. 1 magnitude.

e. None of these.

4. Cluster X has a higher fraction of main-sequence stars than cluster Y. Which cluster is probably older?

a. Cluster X is younger than cluster Y.*

b. Cluster X is the same age as cluster Y.

c. Cluster X is older than cluster Y.

d. We do not have enough information to determine which cluster is older.

e. None of these.

5. How do bursters get their name?

a. Because bursts of x-rays are emitted from them.*

b. Because bursts of ultraviolet rays are emitted from them.

c. Because bursts of infrared rays are emitted from them.

d. Because bursts of radio waves are emitted from them.

e. None of these.

6. In order to find the masses of stars in a binary system, you must know

a. their orbital period

b. their separation from each other

c. their distances from the center of mass

d. all of the above *

7. Imagine that you observed a binary star system face on, so that you are looking directly down on the orbital plane. What do you expect of the Doppler shift from this system?

a. always show red shifts

b. always show blue shifts

c. alternate between red and blue shifts

d. show no Doppler shift at all *