Practice Exam 2 Solutions

Answers are in bold:

1. The spectral sequence of stars from hottest to coolest is

  1. MKGFABO.
  2. OBAFGKM.
  3. MAKGOBF.
  4. FAKGOMB.

2. A cloud of gas located directly between an observer and a hot, dense light source (such as a black body) will produce

  1. an absorption (dark line) spectrum.
  2. a continuous spectrum.
  3. an emission (bright line) spectrum.
  4. pure white light.

3. If the distance between the earth and the Sun were suddenly increased by four times (to 4 AU instead of 1 AU), the gravitational force between them would become

  1. 16 times stronger.
  2. 8 times stronger.
  3. 1/8 as strong.
  4. 1/16 as strong.

4. Sunspots are dark because

  1. regions of the photosphere are blocked by material in the chromosphere.
  2. the local magnetic field cools the currents of hot gas rising from below.
  3. shock waves from the convective region are rising through the photosphere.
  4. the Sun’s equatorial regions are rotating at a different speed than the poles.

5. A star moving towards the earth will have a spectrum containing

  1. weak Balmer lines.
  2. redshifted lines.
  3. blueshifted lines.
  4. unshifted lines.

6. The nuclear reaction responsible for a giant star’s renewed source of energy once electron degeneracy is broken is the

  1. the proton-proton chain.
  2. the CNO cycle.
  3. the triple-alpha process.
  4. shell narrowing.

7. Stars on the main sequence

  1. are all approximately the same age.
  2. are changing size by gravitational contraction.
  3. are at an intermediate stage between giants and dwarfs.
  4. generate energy by the fusion of hydrogen in their cores.

8. What is the correct order, from highest energy to lowest, of the following types of electromagnetic radiation?

  1. visible light, radio, microwave, x-ray
  2. radio, infrared, ultraviolet, gamma ray
  3. infrared, visible light, x-ray, microwave
  4. gamma ray, ultraviolet, infrared, microwave

9. Absolute magnitude is the

  1. apparent magnitude of a star as seen from 10 parsecs away.
  2. luminosity of a star as seen from the center of our galaxy.
  3. apparent magnitude of a star as seen from Earth.
  4. diameter of a star as seen through a telescope.

10. Parallax of a nearby star is used to determine its

  1. apparent magnitude.
  2. physical size or diameter.
  3. surface (effective) temperature.
  4. distance from Earth.

11. A typical Hertzsprung-Russell diagram would plot which of the following stellar properties?

  1. Effective temperature and mass
  2. Spectral class and absolute magnitude
  3. Mass and luminosity
  4. Luminosity and absolute magnitude

12. A planetary nebula is

  1. a thin shell of ejected gases glowing by the light of a central white dwarf star.
  2. a gaseous cloud surrounding a young star during the stage of planet formation.
  3. the filamentary cloud of debris ejected by a star when it becomes a supernova.
  4. the cloud out of which a young planet’s atmosphere will eventually develop.

13. In an H-R diagram, 90 percent of all stars plotted fall

  1. in the giant branch.
  2. on the main sequence.
  3. in the supergiant region.
  4. among the type F stars.

14. What changes would you expect to see in the resulting spectrum of emitted light from a piece of metal when it is heated slowly in an intense flame from 2,500K to 5,00K?

  1. Intensity of radiation would increase greatly and its color would change from red through yellow to white.
  2. Intensity of radiation would increase greatly and its color would change from blue through yellow to red.
  3. Intensity of radiation would increase greatly and its color would remain red.
  4. Intensity of radiation would change only slightly and its color would change from yellow through white to red.

15. Newton stated that if a force were applied to an object in space, the resulting acceleration would depend upon:

  1. the mass of the object.
  2. the weight of the object.
  3. the initial velocity of the object.
  4. the size of the object.

16. The evolution of a star depends predominantly upon its

  1. diameter.
  2. initial mass and composition.
  3. effective temperature.
  4. location in the galaxy.

17. How long will the Sun have spent on the main sequence when it finally begins to evolve toward the red giant branch?

  1. 10 million years
  2. 100 million years
  3. 10 billion years
  4. 100 billion years

18. What are the main products of helium burning (fusion) in a giant star?

  1. carbon and oxygen
  2. iron group elements
  3. hydrogen and electrons
  4. alpha particles

19. What physical phenomenon keeps a white dwarf from collapsing inward upon itself?

  1. normal gas pressure
  2. the physical size of the nucleus
  3. electron degeneracy
  4. convection currents

20. The number of sunspots on the Sun varies with time in what manner?

  1. They increase and decrease every six month
  2. They increase and decrease every year
  3. They increase and decrease on an 22 year cycle
  4. They increase and decrease with no predictable pattern

21. The order of the layers of our Sun as the radius increases is

  1. radiative zone, convective zone, corona, chromosphere, photosphere
  2. radiative zone, thermonuclear core, corona, chromosphere, photosphere
  3. convective zone, radiative zone, corona, chromosphere, photosphere
  4. thermonuclear core, convective zone, photosphere, chromosphere, corona

22. The approximate surface temperature of our Sun is

  1. 4,500K.
  2. 5,700K.
  3. 5,000,000K.
  4. 15,600,000K.

23. The specific colors of light emitted by an atom in a hot, thin gas are caused by

  1. protons jumping from one energy level to the next.
  2. an electron falling into the nucleus.
  3. vibrations of the electrons within the atom.
  4. electrons cascadiing from higher energy levels to lower levels.

24. The thermonuclear process believed to be responsible for creating the Sun’s energy involves the conversion of

  1. lead to gold.
  2. uranium to plutonium.
  3. helium to carbon.
  4. hydrogen to helium.

25. The luminosity of a star is a unique measure of its

  1. total energy output per second.
  2. velocity through space.
  3. core temperature.
  4. diameter.

Solutions to Practice Exam 2