1. If we know both the apparent magnitude and absolute magnitude of a star, we can determine its
   (A) tempertaure.
   (B) radius.
   (C) magnetic field.
   (D) distance.
   (E) all of the above.

2. What is the most common type of stars within 500 pc from the Sun?
   (A) O and B dwarfs
   (B) A and B dwarfs
   (C) A and B giants
   (D) G dwarf and giants
   (E) M dwarfs

3. The mass of a star can be determined from observations of
   (A) the orbital motion of binary stars.
   (B) a star's magnetic cycle.
   (C) a star's brightness.
   (D) a star's rotation.
   (E) a star's color.

4. A star's luminosity depends on what two characteristics?
   (A) its metal abundance and its density.
   (B) its density and temperature.
   (C) temperature and distance.
   (D) size and temperature.
   (E) distance and size.

5. The main sequence is a sequnce of
   (A) spectral type
   (B) stellar temperature
   (C) stellar luminosity
   (D) stellar mass
   (E) all of the above

6. If a star in the solar neighborhood has a space velocity perpendicular to the disk of the Galaxy, this star is most likely
   (A) a star in the disk of the Galaxy.
   (B) a star from the halo of the Galaxy.
   (C) a star from the bulge of the Galaxy.
   (D) an O star.
   (E) a B star.

7. In a cluster, which of the following properties can be different among the stars?
   (A) age.
   (B) mass.
   (C) distance.
   (D) abundances.
   (E) none of the above.

8. The HR diagram of a cluster can be used to determine
   (A) the total mass of the cluster.
   (B) the distance of the cluster
   (C) the magetic field of the cluster.
   (D) the space velocity of the cluster.
   (E) all of the above.

9. Molecular clouds are best observed with spectral lines of
   (A) hydrogen molecule.
   (B) helium atom.
   (C) carbon monoxide.
   (D) amonia.
   (E) water.

10. Neutral atomic clouds of the interstellar medium is best observed in the 21-cm line emitted when the electron in a hydrogen atom
    (A) changes orbital radius.
    (B) makes a transition to a higher energy level.
    (C) reverses its orbital motion around the nucleus.
    (D) changes its spin from parallel to opposite to the nucleus' spin.
    (E) changes its spin from opposite to parallel to the nucleus' spin.

11. A star viewed through a dust cloud would appear
    (A) redder and cooler.
    (B) bluer and brighter.
    (C) redder and dimmer.
    (D) bluer and hotter.
    (E) the same.

12. Reflection nebulae are
    (A) orange due to reddening from interstellar dust.
    (B) red due to emission from embedded M stars.
    (C) blue due to Lyman alpha line emission.
    (D) blue due to reflected light from B stars.
    (E) red due to H-alpha line emission.

13. A cloud contracts to become a star because its _____ is greater than its _____.
    (A) gravity, pressure
    (B) gravity, orbital velocity
    (C) pressure, orbital velocity
    (D) magnetic field, pressure
    (E) pressure, gravity

14. A brown dwarf is
    (A) a main sequence star with a thick dusty atmosphere.
    (B) a star that burns deuterium but not hydrogen.
    (C) a cooler binary companion of a white dwarf.
    (D) a cooled white dwarf.
    (E) a rocky planet.

15. What is responsible for dissociating molecules and ionizing atoms in the interstellar medium?
    (A) Solar winds from stars like our Sun.
    (B) infra-red radiation from brown dwarfs.
    (C) ultraviolet radiation from O and B stars.
    (D) visible light emitted by main sequence stars.
    (E) X-ray and gamma-ray emission from stars of all spectral types.

16. Stars are most likely to be formed in
    (A) molecular clouds.
    (B) neutral atomic clouds.
    (C) emission nebulae.
    (D) reflection nebulae.
    (E) coronal gas.

    HR Diagram

    
    For the following questions, use the HR Diagram above. For each question, write down the letter which corresponds to the proper location on the diagram. E is "none of the above". W, X, Y, and Z are stars labelled by the black filled circles.

17. Which is the main sequence?  C

18. Where are the largest (radius) stars? A

19. Where are the smallest stars?  D

20. Where are Luminosity class I stars?  A

21. The sun is at which location?
    (A) W
    (B) X
    (C) Y
    (D) Z
    (E) none of the above

22. Star W and star Z have the same
    (A) color.
    (B) brightness.
    (C) mass.
    (D) age.
    (E) magnetic field.

23. The radius of star W is ____ the radius of star Z.
    (A) the same as
    (B) larger than
    (C) smaller than
    (D) either larger or smaller depending on its distance
    (E) indeterminate compared to

24. Star Y is ____ than star Z.
    (A) cooler
    (B) less massive
    (C) bluer
    (D) all of the above
    (E) none of the above

25. Star W is ____ than star Y.
    (A) hotter
    (B) more massive
    (C) bluer
    (D) all of the above
    (E) none of the above

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