VERSION A

Write your name at the top of this quiz as well as on your answer sheet. WRITE YOUR VERSION ON YOUR ANSWER SHEET. Feel free to write or draw on the quiz.

PICK THE BEST ANSWER FOR EACH PROBLEM.

1. Which of the following types of stars have main sequence lifetimes longer than the current age of the Universe?
a) 09V.
b) M5V.
c) A1V.
d) G2V.
e) B1V.

b) M5V.

2. A planetary nebula is:
a) An ionized interstellar gas cloud seen around a main sequence O star.
b) A blue glowing cloud around a main sequence B star.
c) An ionized gas shell around the burned-out core of a star like the Sun.
d) A remnant of the explosion of a high mass star.
e) A flattened disk of dust and gas with a protostar in the core.

c) An ionized gas shell around the burned-out core of a star like the Sun.

3. The red glowing emission seen throughout the Orion nebula is caused by:
a) starlight scattering off interstellar dust.
b) thermal radiation from interstellar dust.
c) radiation from the spin-flip of an electron in a hydrogen atom.
d) a very strong Doppler shift.
e) the strong red H-alpha emission line from hydrogen gas.

e) the strong red H-alpha emission line from hydrogen gas.

4. What is one way that molecular clouds are detected?
a) The 21 cm line of HI.
b) The H-alpha line from hydrogen.
c) The H-beta line from hydrogen.
d) The 2.6 millimeter line of CO.
e) No molecular clouds have been detected so far, although they are hypothesized to exist.

d) The 2.6 millimeter line of CO.

5. Which of the following is a good way to determine the sizes of stars?
a) measurements of proper motion.
b) the 2.6 millimeter line of CO.
c) the light curves of eclipsing binaries.
d) the motions of visual binaries in the sky.
e) the motions of astrometric binaries in the sky.

c) light curves of eclipsing binaries.

6. A brown dwarf is:
a) a very cold main sequence star.
b) the burned-out core of a star like the Sun.
c) a cooled-off white dwarf.
d) an object with too low mass to become a star.
e) an extrasolar planet.

d) an object with too low mass to become a star.

7. Thermal radiation from cold interstellar dust peaks in the:
a) UV.
b) X-ray.
c) optical.
d) gamma ray.
e) far-infrared.

e) far-infrared.

8. From the bottom to the top of the main sequence, the luminosity increases by a factor of 10⁷. By what factor does the mass increase?
a) 400
b) 10⁷
c) 10¹⁴
d) 10
e) The masses of all main sequence stars are about the same.

a) 400

9. The very strong emission line at 21 cm detected by radio telescopes is produced by:
a) neutral atomic hydrogen.
b) ionized hydrogen.
c) molecular hydrogen.
d) carbon monoxide.
e) interstellar dust.

a) neutral atomic hydrogen.

10. Inspect the H-R diagram to the right. Stars that lie at position Z are luminosity class:
a) I.
b) II.
c) III.
d) IV.
e) V.

e) V.

11. The triple-alpha process involves the fusion of three:
a) positrons.
b) deuterium nuclei.
c) hydrogen-1 nuclei.
d) helium-3 nuclei.
e) helium-4 nuclei.

e) helium-4 nuclei.

12. A star cluster is observed to have a main sequence that extends up to G stars, with no more luminous main sequence stars seen. Approximately how old is this cluster?
a) A few million years old.
b) 100 million years old.
c) 1 billion years old.
d) 10 billion years old.
e) 1 trillion years old.

d) 10 billion years old.

13. When helium fusion begins in a one solar mass star, the star becomes a:
a) white dwarf.
b) horizontal branch star.
c) red giant star.
d) main sequence star.
e) brown dwarf.

b) horizontal branch star.

14. What is the last evolutionary step for a one solar mass star, just before it becomes a planetary nebula?
a) red giant star.
b) asymptotic giant branch star.
c) horizontal branch star.
d) subgiant star.
e) main sequence star.

b) asymptotic giant branch star.

15. Uranium is produced:
a) in main sequence stars.
b) in horizontal branch stars.
c) in supernova explosions.
d) in asymptotic giant branch stars.
e) in white dwarfs.

c) in supernova explosions.

16. Looking at the periodic table on the wall, determine what is produced when an alpha capture process happens to ¹²C?
a) ¹⁶O
b) ²⁰O
c) ¹⁶N
d) ¹⁶Si
e) ²⁰Si

a) ¹⁶O

17. Over its lifetime, our Sun will go through various evolutionary phases. What kind of object will it *NEVER* become?
a) white dwarf.
b) asymptotic giant branch star.
c) supernova type II.
d) horizontal branch star.
e) red giant star.

c) supernova type II.

18. Besides its main sequence phase, a star like the Sun only has nuclear reactions in its very central core during one other phase in its lifetime. What phase?
a) as a white dwarf.
b) as a horizontal branch star.
c) as a red giant star.
d) as an asymptotic giant branch star.
e) as a planetary nebula.

b) as a horizontal branch star.

19. The Pleiades star cluster contains many main sequence B stars, but no O stars. In contrast, the NGC 6705 cluster contains both O and B stars, and the Praesepe cluster contains neither. The relative ages of the three clusters is therefore (from youngest to oldest):
a) Pleiades; NGC 6705; Praesepe.
b) NGC 6705; Pleiades; Praesepe.
c) Praesepe; Pleiades; NGC 6705.
d) It is impossible to tell the relative ages of the three clusters with the given information.
e) All three clusters are the same age.

b) NGC 6705; Pleiades; Praesepe.

20. White dwarfs are stable due to the inward force of gravity from the mass of the star being balanced by:
a) internal gas pressure resulting from nuclear reactions.
b) degenerate neutron pressure.
c) degenerate electron pressure.
d) angular momentum.
e) inertia.

c) degenerate electron pressure.