1. Inspect the H-R diagram to the right. Stars that lie at position X:
a) have main sequence lifetimes of about trillion years.
b) have main sequence lifetimes of 10 billion years.
c) have main sequence lifetimes of 1 billion years.
d) have main sequence lifetimes of 1 million years.
e) live forever.

2. What produces the strong 21 cm radio line seen from interstellar clouds?
a) atomic hydrogen.
b) ionized hydrogen.
c) molecular hydrogen.
d) carbon monoxide.
e) interstellar dust.

3. In the Horsehead Nebula, the dark feature that makes the shape of the horse's head is:
a) An interstellar cloud that is 99 percent interstellar dust by mass.
b) An interstellar cloud that is 75 percent hydrogen gas, 24 percent helium gas, by mass, and one percent dust and other chemical elements.
c) An interstellar cloud that is about half hydrogen and half dust by mass.
d) An interstellar cloud that is 99 percent carbon monoxide by mass.
e) An interstellar cloud that is 99 percent carbon by mass.

4. Where are HII regions located?
a) Around brown dwarfs.
b) Around GV stars.
c) Around AV stars.
d) Around OV stars.
e) Around red supergiant stars.

5. In what wavelength regime is the peak of the thermal spectrum of interstellar dust grains?
a) Infrared.
b) Optical.
c) X-ray.
d) Ultraviolet.
e) Gamma Rays.

6. Why do HII regions take on a reddish appearance in photographs?
a) Because of the hydrogen H-alpha line.
b) Because dust in the HII region preferentially scatters out blue light.
c) Because the temperature of the nebula is such that the peak of its thermal spectrum is in the red part of the spectrum.
d) They contain many very red stars, whose starlight dominates the light from the HII region.
e) They are very cold (about 100K), and therefore emit most of their light in the infrared, with just a little in the optical (mainly in the red part of the spectrum). Since photographic emulsion is not sensitive to infrared light, they appear red in photographs.

7. Most of the extrasolar planets discovered so far have been found by:
a) direct observation of the planet.
b) observation of the spectrum of the planet.
c) observation of a `wobble' in the position of the planet's star with time.
d) periodic redshifting and blueshifting of the light from the planet's star.
e) observation of a periodic dimming of the light from the planet's star due to eclipses by the planet.

8. Masses of stars can be measured by:
a) weighing them on a scale.
b) observing the motion of a single star as it moves through space.
c) monitoring the light curve of a variable star.
d) measuring the orbital period, Doppler shift, and separation of a visual binary.
e) wait for the star to pass near the Earth and send a spacecraft.

9. A brown dwarf is:
a) A very luminous star (10,000 solar luminosities) but very small star (0.1 solar radii).
b) A very luminous star (10,000 solar luminosities) with a temperature about 30,000K.
c) A low luminosity object (less than or equal to 0.01 solar luminosities) with a temperature about 30,000K.
d) A low mass object (less than 0.08 solar masses), with no nuclear fusion inside except perhaps deuterium fusion.
e) A white dwarf star.

10. Which of the following statements is true about the lifetimes of main sequence stars?
a) Lower luminosity main sequence stars live longer than higher luminosity main sequence stars.
b) Main sequence A stars live longer than main sequence K stars.
c) Hot main sequence stars live longer than cool main sequence stars.
d) The greater the mass of a star, the longer its main sequence lifetime.
e) All main sequence A stars ever formed are still main sequence A stars.

11. The uranium on Earth was probably produced:
a) in the core of the Sun.
b) in the core of a red giant.
c) in a white dwarf.
d) in a planetary nebula.
e) in a supernova explosion.

12. The most common elements in the Universe are:
a) hydrogen and helium.
b) carbon and oxygen.
c) iron and silicon.
d) carbon and iron.
e) carbon, nitrogen, and oxygen.

13. MV stars are:
a. the hottest known stars.
b. brown dwarfs.
c. very short-lived stars.
d. inert balls of carbon.
e. fusing hydrogen to helium in their cores.

14. The following H-R diagram shows the evolutionary track of a massive star. At the marked position along the track, what is occuring?
a) core hydrogen burning.
b) shell hydrogen burning.
c) core helium burning.
d) shell hydrogen and helium burning.
e) no nuclear reactions.

15. Extrasolar planets:
a) is the generic name for the four largest planets: Jupiter, Saturn, Uranus, or Neptune.
b) are white dwarfs.
c) Can be found by observing their gravitational effect on their star.
d) May exist, but have never been found.
e) Probably do not exist.

16. The following events occur in a massive star (mass greater than about 8 solar masses) during its lifetime.

1. carbon fusion in the core.
2. carbon fusion in a shell surrounding a shrinking inert oxygen core.
3. hydrogen fusion in the core.
4. explosion as a supernova.
5. silicon burning in the core.
6. radioactive decay of ⁵⁶Ni in the core.

17. The age of a star cluster is equal to:
a) The main sequence lifetime of the lowest mass star in the cluster.
b) The main sequence lifetime of the star at the top of the observed main sequence in the H-R diagram of the star cluster.
c) The time that it takes a main sequence M star to evolve to the top of the observed Asymptotic Giant Branch in the H-R Diagram of the star cluster.
d) All star clusters in the Milky Way formed about 1 million years ago.
e) All star clusters in the Milky Way are 13.7 billion years old.

18. An alpha capture reaction is:
a) When an ion combines with an electron.
b) When an electron and a proton combine to form a neutron and a neutrino.
c) When a helium nucleus fuses with a heavier nucleus (such as an oxygen nucleus).
d) During a supernova, when a neutron fuses with an atom.
e) When four hydrogen nuclei fuse to form a helium nucleus.

19. The angular momentum of a spinning object is proportional to its:
a) mass X radius.
b) mass X spin velocity.
c) mass X spin velocity X radius.
d) mass X spin velocity X radius².
e) mass X spin velocity² X radius.

20. Which of the following chemical elements is more abundant in the Universe?
a) Sulfur.
b) Nitrogen.
c) Uranium.
d) Iron.
e) Carbon.

21. Note the H-R diagram to the right. A star that lies at the marked position has:
a) hydrogen fusion in its core.
b) helium fusion in its core.
c) no nuclear reactions in its core, but shell hydrogen fusion.
d) a radius that is shrinking with time.
e) no nuclear reactions.

22. A protostar:
a) is extremely hot (about 30,000K).
b) is spinning more slowly than the interstellar cloud it formed from.
c) emits large quantities of ultraviolet radiation.
d) emits large quantities of X-ray radiation.
e) has a spectrum that peaks in the infrared regime.

23. The linear momentum of an object moving in a straight line is proportional to its:
a) mass X radius.
b) mass X velocity.
c) mass X velocity X radius.
d) mass X velocity X radius².
e) mass X velocity².

24. Looking at the periodic table on the wall, determine what is produced when an alpha capture process happens to ²⁴Mg?
a) ²⁶Mg
b) ²⁶Si
c) ²⁸Al
d) ²⁸Si
e) ²⁸S

25. Which of the following chemical elements is more abundant in the Universe?
a) Uranium.
b) Silicon.
c) Iron.
d) Helium.
e) Carbon.

26. White dwarfs are made up of mainly:
a) neutrons.
b) hydrogen.
c) helium, carbon, and/or oxygen.
d) silicon, magnesium, and nickel.
e) iron.

27. The iron in our blood was probably originally produced:
a) in a main sequence star.
b) in one solar mass stars, just after they leave the main sequence.
c) in a one solar mass star, while it is on the asymptotic giant branch.
d) during the formation of a planetary nebula.
e) in a massive star, just before it explodes as a supernova.

28. Which of the following types of stars has the longest main sequence lifetime?
a) O9V.
b) M5V.
c) K3V.
d) G2V.
e) B3V.

29. The mass of an OV star is about:
a) 10⁴ solar masses.
b) 40 solar masses.
c) 2 solar masses.
d) 1 solar mass.
e) 0.1 solar masses.

30. Approximately how long does it take before the hydrogen runs out in the core of a G2V star?
a) 3 million years.
b) 10 million years.
c) 10 billion years.
d) a trillion years.
e) a hundred trillion years.

31. Which of the following types of stars has the biggest mass?
a) M5V.
b) K3V.
c) G2V.
d) B3V.
e) O9V.

32. The interstellar medium is:
a) always very cold, about 10K.
b) about 99 percent hydrogen and helium.
c) about half gas, half dust.
d) about 99 percent dust, 1 percent gas.
e) completely ionized.

33. The main sequence lifetime of an O star is about:
a) a thousand years.
b) a few million years.
c) 10 billion years.
d) 100 billion years.
e) a trillion years.

34. To detect cold neutral interstellar atomic clouds (i.e., HI clouds), the best method is to search for:
a) The red H-alpha line.
b) The blue/green H-beta line.
c) The 21 cm radio line of hydrogen.
d) the 2.6 millimeter line of carbon monoxide.
e) a diffuse reddish glow in an astronomical photograph.

35. The reddish glowing nebula that is visible around main sequence O stars is called a:
a) HI cloud.
b) HII region.
c) molecular cloud.
d) dark cloud.
e) reflection nebula.

36. What is the relationship between the mass and the luminosity of a main sequence star, approximately?
a) the luminosity is inversely proportional to the mass.
b) the luminosity is inversely proportional to the mass squared.
c) the luminosity is proportional to the mass.
d) the luminosity is proportional to the mass to the fourth power.
e) the luminosity does not depend upon mass; all main sequence stars have the same mass.

37. Which of the following techniques is NOT a viable method for detecting interstellar dust?
a) thermal radiation in the far-infrared from the dust grains.
b) thermal radiation in the optical from the dust grains.
c) scattered blue starlight from the dust grains.
d) absorption of optical light by the dust grains.
e) reddening of background stars due to intervening dust.

38. An alpha particle is:
a) an ionized hydrogen atom.
b) a ²H nucleus.
c) a ⁴He nucleus.
d) a carbon-12 nucleus.
e) an ⁵⁶Fe nucleus.

39. A white dwarf has:
a) a mass of more than 3 solar masses and a diameter about the same as that of the Earth.
b) a mass between 1.4 and 3 solar masses and a diameter of about 20 km.
c) a mass between 1.4 and 3 solar masses, and a diameter about the same as that of the Earth.
d) a mass less than 1.4 solar masses, and a diameter about the same as that of the Earth.
e) a mass less than 1.4 masses, and a diameter of about 20 km.

40. Which of the following is closest in diameter to a white dwarf?
a) the orbit of the Earth around the Sun.
b) the Sun.
c) the Earth.
d) Johnson City.
e) the head of a pin.

41. In which of the following does electron degeneracy pressure hold the core up against gravity?
a) a red giant star, just before the triple-alpha process starts in the core.
b) a high mass main sequence star.
c) a brown dwarf.
d) a one solar mass main sequence star.
e) a horizontal branch star.

42. The plutonium on Earth was probably produced:
a) in the core of the Sun.
b) in the core of a red giant.
c) in a white dwarf.
d) in a planetary nebula.
e) in a supernova explosion.

43. Asymptotic giant branch stars:
a) have hydrogen fusion in their cores.
b) have helium fusion in their cores.
c) are unstable stars soon to become planetary nebulae.
d) have cores made up solely of neutrons, packed closely together.
e) probably have black holes in their centers.

44. What is the CNO cycle?
a) the process by which helium is fused into carbon, nitrogen, and oxygen.
b) the process by which carbon is fused into nitrogen and oxygen.
c) a type of hydrogen fusion which uses carbon, nitrogen, and oxygen atoms as catalysts.
d) the period of a massive stars's life, when carbon, oxygen, and nitrogen are fusing in shells around the core.
e) the period of a low-mass stars's life after all the carbon, oxygen, and nitrogen have been converted into heavier chemical elements.

45. Which of the following statements about supernovae is correct?
a) our Sun will eventually become a supernova.
b) most stars eventually explode as supernova.
c) one or two supernova are seen in the Milky Way per year.
d) about 100 Milky Way supernovae are seen per year.
e) supernovae occur approximately once every couple of hundred years in the Milky Way.

46. The following H-R diagram shows the evolutionary track of a massive star. When the star reaches the marked position along the track, what nuclear reaction begins for the first time?
a) core hydrogen burning.
b) shell hydrogen burning.
c) core helium burning.
d) core oxygen fusion.
e) core carbon fusion.

47. Which of the following types of stars have main sequence lifetimes of about 1 billion years?
a) 09V.
b) M5V.
c) A1V.
d) G2V.
e) K3V.

48. An HII region is a/an:
a) Ionized interstellar gas cloud seen around a main sequence O star.
b) Cold interstellar atomic hydrogen cloud.
c) Ionized interstellar gas cloud seen around the burned-out core of a star like the Sun.
d) Remnant of a supernova explosion.
e) Molecular cloud.

49. Which of the following objects is best described as a reflection nebula?
a) the red glowing cloud around the O stars in the Orion Nebula.
b) the horse's head in the Horsehead Nebula.
c) the glowing shell of gas and dust surrounding the core of a dying star.
d) the cloud of material left-over after a supernova explosion, for example, the Crab Nebula.
e) The glowing blue clouds seen around the stars in the Pleiades star cluster.

50. The 2.6 millimeter line of the carbon monoxide molecule is often used as a way to find:
a) HI clouds.
b) HII regions.
c) Supernova remnants.
d) Planetary Nebulae.
e) Molecular Clouds.

51. What information can be obtained if an extrasolar planet is observed transiting its star?
a) Whether or not it is inhabited.
b) Its temperature.
c) Its physical diameter.
d) Its distance from Earth.
e) All of the above.

52. What do Astronomers call an object with a mass between about 0.013 solar masses and 0.08 solar masses, that never became a star?
a) a white dwarf.
b) a brown dwarf.
c) a black dwarf.
d) a Jovian planet.
e) an extrasolar planet.

53. The H-alpha line of hydrogen:
a) is 21 cm in wavelength.
b) produces the blue glow seen around the stars in the Pleiades star cluster.
c) produces the red glow seen from hot ionized interstellar gas clouds.
d) is a very strong yellow line.
e) is extremely strong from molecular clouds.

54. Observationally, how can one distinguish a B star that lies behind an interstellar cloud from an unobscured G star?
a) from their Doppler shifts.
b) from their spectra.
c) from their B - V colors.
d) from their proper motions.
e) all of the above.

55. The very bright `glow' from interstellar clouds at about 100 microns, in the far-infrared, is due to:
a) the H-alpha line of hydrogen.
b) thermal emission from interstellar dust grains.
c) radiation from the spin-flip of electrons in the ground state of atomic hydrogen.
d) the combined light of many white dwarf stars.
e) the combined light of many extrasolar planets.

56. Inspect the H-R diagram to the right. Stars that lie at position Z:
a) have main sequence lifetimes of about a trillion years.
b) have main sequence lifetimes of about 10 billion years.
c) have main sequence lifetimes of about 1 billion years.
d) have main sequence lifetimes of about 1 million years.
e) have main sequence lifetimes of about 100,000 years.

57. What is another name for a helium-4 nucleus?
a) a positron.
b) a deuterium nucleus.
c) a beta particle.
d) an alpha particle.
e) a gamma particle.

58. Which of the following is NOT a way to detect interstellar dust?
a) the 21 cm emission line.
b) the reddening of stars behind interstellar clouds.
c) the scattering of blue starlight.
d) thermal radiation in the far-infrared.
e) the absorption of the light from background stars in the optical.

59. When a one solar mass star has evolved to become an asymptotic giant branch star, which is moving up and to the right on the H-R diagram, what is its internal structure like?
a) An inert neutron core, surrounded by multiple layers of shell burning, with increasingly light chemical elements from silicon to hydrogen.
b) Core helium burning, surrounded by a shell of hydrogen burning.
c) An inert carbon core, surrounded by a shell of helium burning and a shell of hydrogen burning.
d) Hydrogen fusion in the core, surrounded by a shell of helium burning.
e) An iron core, surrounded by multiple layers of shell burning, with increasingly light chemical elements from silicon to hydrogen.

60. The diagram to the right shows the evolutionary path of a star. The star leaves the main sequence, moves up and to the right, then moves back to the left. At the point marked `here', when the star is moving back to the left on the H-R diagram, what is occuring in the core of the star?
a) hydrogen fusion.
b) helium fusion.
c) carbon fusion.
d) no fusion; the core is shrinking.
e) no fusion; the core is held up against gravity by electron degeneracy pressure.

61. Which of the following chemical elements is more abundant in the Universe?
a) Sulfur.
b) Silicon.
c) Uranium.
d) Magnesium.
e) Oxygen.

62. A planetary nebula is:
a) An interstellar gas cloud in the process of creating a star and solar system.
b) The expanding outer layers of a dying star that are ionized by the hot core of the star.
c) A gas cloud created by the explosion of a massive star.
d) A dense molecular cloud.
e) A ionized gas cloud surrounding a main sequence O star.

63. Which of the following elements are ONLY produced during supernova explosions?
a) carbon.
b) oxygen.
c) magnesium.
d) uranium.
e) nitrogen.

64. Looking at the periodic table on the wall, determine what is produced when an alpha capture process happens to ²⁰Ne?
a) ²⁰Mg
b) ²⁴Si
c) ²⁴Mg
d) ²⁸Si
e) ²⁸S

65. What is the ultimate fate of an isolated white dwarf, that does not interact closely with another object?
a) It becomes a brown dwarf.
b) It becomes a black dwarf.
c) It remains the same temperature and size indefinitely.
d) It slowly expands and becomes less dense, until it finally dissipates into the interstellar medium.
e) It continues to contract, until finally it becomes a ball of neutrons.

66. When a one solar mass star first leaves the main sequence, and starts moving through the subgiant (IV) portion of the H-R diagram, what is occuring inside the star?
a) helium fusion in the core, hydrogen fusion in a shell surrounding the core.
b) hydrogen fusion in the core, helium fusion in a shell surrounding the core.
c) no fusion in the core, hydrogen fusion in a shell surrounding the core.
d) no fusion in the core, helium fusion in a shell surrounding the core.
e) carbon fusion in the core, helium fusion in a shell surrounding the core.

Answers: 1b, 2a, 3b, 4d, 5a, 6a, 7d, 8d, 9d, 10a, 11e, 12a, 13e, 14d, 15c, 16c, 17b, 18c, 19c, 20e, 21c, 22e, 23b, 24d, 25d, 26c, 27e, 28b, 29b, 30c, 31e, 32b, 33b, 34c, 35b, 36d, 37b, 38c, 39d, 40c, 41a, 42e, 43c, 44c, 45e, 46c, 47c, 48a, 49e, 50e, 51c, 52b, 53c, 54b, 55b, 56a, 57d, 58a, 59c, 60b, 61e, 62b, 63d, 64c, 65b, 66c.