Download Test #3

Ph109 Exploring the Universe, Test #3, Spring 2005
Please indicate the best answer to the following questions on the answer sheet provided.
1. If the Sun were replaced by a black hole having a mass of one solar mass, what would happen to the Earth's
orbit?
a. the Earth would spiral inward
b. the Earth would jump to a smaller orbit
c. the size of the Earth's orbit would increase rapidly
d. the Earth's orbit would remain the same
2. A neutron star is expected to spin rapidly because
a. they conserved angular momentum when they collapsed.
b. they have high orbital velocities.
c. they have high densities.
d. they have high temperatures.
3. What is the single most important characteristic in determining the course of a star's evolution?
a) Absolute brightness., b) Distance., c) Surface temperature., d) Mass.
4. Sunspots appear dark because
a) they are cooler regions, b) they are concentrations of carbon,
c) their spectrum has been Doppler shifted, d) impurities in the Sun
5. When the electron and proton go from aligned spins to opposite spins in the Hydrogen atom, what happens?
a) nuclear fusion, b) nuclear fission, c) 21 cm radiation, d) E=MC 2
6. By what factor would the brightness of a star increase if an observer moved from 3 parsecs to 1 parsec from the star?
a) 3 times, b) 9 times, c) 27 times, d) 81 times
7. What is the general name for stars which are converting hydrogen into helium in their cores?
a) main sequence stars, b) red giant stars, c) white dwarf stars, d) protostars
8. Stars on the main sequence with the greatest mass
a. are spectral type M stars. b. are spectral type O stars.
c. are located at the bottom of the main sequence in the HR diagram. d. have masses very similar to the sun.
9. Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?
a. hydrogen, b. hydrogen and helium, c. hydrogen, helium and carbon
d. hydrogen, helium, carbon, and neon, e. hydrogen, helium, carbon, neon, and oxygen.
10. A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion.
c. produced by a nova explosion.
d. a nebula within which planets are forming.
11. Pulsars cannot be spinning white dwarfs because
a. white dwarfs are not that common. b. white dwarfs are not dense enough.
c. white dwarfs do not have magnetic fields. d. a white dwarf spinning that fast would fly apart
12. Which element is the Sun currently fusing
a. Hydrogen, b. Helium, c. Carbon, d. Oxygen
13. What will be the last element that the Sun will be able to "burn"
a. Hydrogen, b. Helium, c. Carbon, d. Oxygen
14. The total mass of a binary system can be calculated from
a. the ratio of the angular separation from the center of mass of each of the stars.
b. the distance to the binary and its radial velocity.
c. the semi major axis and period of the orbit.
d. the radial velocities of the two stars.
15. Blue stars are _____ than red stars
a. hotter b. cooler c. larger d. smaller
16. About how old is our Sun?
a. 10 million years b. 5 billion years c. 10 billion years d. 1 million years
17. Which spectral type of star has not yet lived long enough to have evolved?
a. O b. B c. M d. G
18. The primary reason for the 22 year sunspot cycle is
a. Orbit of Jupiter, b. Alignment of the planets every 22 years.
c. magnetic field reversal d. enhanced synchrotron radiation
19. What spectral class is our Sun?
a. O b. B c. M d. G
20. The temperature of the photosphere of our Sun is about
a) 1,000 degrees, b) 5,000 degrees, c) 10,000 degrees, d) 15,000 degrees
21. How would a sunspot look if we could remove it from the Sun?
a) It is dark, so it would disappear into the night.
b) It would be bright orange, as bright as the full moon
c) It would look like a bright planet, shining by reflected sunlight
d) It would not appear very different than the rest of the Sun.
22. What information can be gained from the light curves of eclipsing binaries?
a) their distances , b) their masses , c) their sizes , d) their temperatures , e) their luminosities
23. The spectral type of a star measures its:
a) luminosity. , b) chemical composition. , c) size. , d) temperature. , e) mass
24. The H-R diagram can plot:
a) temperature versus mass. , b) radius versus luminosity. , c) temperature versus luminosity.
d) apparent magnitude versus spectral classes. , e) radius versus mass
25. On the H-R diagram, our Sun lies:
a) at the top left. , b) at the top right. , c) about the middle. , d) at the bottom left. , e) at the bottom right.
26. On the H-R diagram, the white dwarfs Sirius B and Procyon B lie:
a) at the top left. , b) at the top right. , c) in the middle of the main sequence. ,
d) at the lower left of the main sequence. , e) to the bottom right on the main sequence
27. Some regions along the plane of the Milky Way appear dark because:
a) there are no stars in these areas. , b) stars in that region are hidden by interstellar gas.
c) stars in that region are hidden by dark dust particles. , d) many brown dwarfs in those areas absorb light.
28. If we counted all the stars that are currently on the main sequence, which spectral type would be most abundant?
a. A, b. B, c. K, d. M
29. What mechanism is responsible for the twisting of the Sun's magnetic filed lines?
a. differential rotation, b. convection, c. proton-proton cycle, d. tidal forces
30. Sunspots usually occur
a. as single regions, b. in pairs,
c. in groups of three or more, d. as continuous regions around the sun's equator
31. Which of the following stars is most dense?
a. a supergiant star, b. a main sequence star,
c. a giant star, d. a white dwarf
32. Giant and supergiant stars are rare because
a. they do not form as often as main sequence stars.
b. the giant and supergiant stage is unstable.
c. the giant and supergiant stage is very short.
d. helium is very rare.
33. Why don't all supernova remnants contain pulsars?
a. All supernova remnants do contain pulsars.
b. Some supernova explosions form white dwarfs instead of the neutron stars necessary for pulsars.
c. Pulsars slow down and quite producing the pulses before the supernova remnant dissipates.
d. The pulsar may be tipped so that the beams do not sweep past Earth.
34. Synchrotron radiation is produced by
a. objects with temperature below 10,000 K.
b. high-velocity electrons moving through a magnetic field.
c. cold hydrogen atoms in space.
d. the collapsing cores of massive stars.
35. Massive stars cannot generate energy through iron fusion because
a. iron fusion requires very high density.
b. stars contain very little iron.
c. no star can get hot enough for iron fusion.
d. massive stars supernova before they create an iron core.
36. Which event marks the birth of a star?
a) Fusion of hydrogen atoms into helium atoms., b) Collapse of an interstellar cloud.
c) Formation of a photosphere., d) Instability in an interstellar cloud.
37. The observed slowing of a clock in the vicinity of a black hole is a prediction of:
a) Special relativity, b) General relativity, c) Stellar nucleosynthesis, d) The Principle of Cosmic Censorship.
38. What explanation does general relativity provide for gravity?
a) Gravity is a result of curved spacetime., b) Gravity is directly proportional to mass.
c) Gravity is inversely proportional to radius., d) Gravity is stronger the faster you go.
39. In relative terms, how does the Sun's size compare to all other stars
a) tends to be on the smaller side, b) tends to be on the larger side,
c) tends to be in the middle, d) we can't measure the size of other stars
40. In relative terms, how does the Sun's temperature compare to all other stars
a) tends to be on the hot side, b) tends to be on the cool side,
c) tends to be in the middle, d) we can't measure the temperatures of other stars