# Astronomy college course/Unit 4 study guide

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## AstroTest4_Study

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### AstroTest4_Study-v1s1

1. Stellar parallax is
    ___ a) a numerical measure of brightness as seen from Earth
    ___ b) an annual change in angular position of a star as seen from Earth
    ___ c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
    ___ d) the total amount of energy emitted per unit time.
    ___ e) an astronomical object with known luminosity.
2. Luminosity is
    ___ a) the total amount of energy emitted per unit time.
    ___ b) an annual change in angular position of a star as seen from Earth
    ___ c) a numerical measure of brightness as seen from Earth
    ___ d) a numerical measure of brightness as seen from a distance of approximately 33 light-years
    ___ e) an astronomical object with known luminosity.
3. A standard candle is
    ___ a) a numerical measure of brightness as seen from a distance of approximately 33 light-years
    ___ b) the total amount of energy emitted per unit time.
    ___ c) an annual change in angular position of a star as seen from Earth
    ___ d) a numerical measure of brightness as seen from Earth
    ___ e) an astronomical object with known luminosity.
4. Absolute magnitude is
    ___ a) an astronomical object with known luminosity.
    ___ b) the total amount of energy emitted per unit time.
    ___ c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
    ___ d) an annual change in angular position of a star as seen from Earth
    ___ e) a numerical measure of brightness as seen from Earth
5. Relative magnitude is
    ___ a) the total amount of energy emitted per unit time.
    ___ b) a numerical measure of brightness as seen from a distance of approximately 33 light-years
    ___ c) an astronomical object with known luminosity.
    ___ d) a numerical measure of brightness as seen from Earth
    ___ e) an annual change in angular position of a star as seen from Earth
6. In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions allowing measurements of stellar parallax for stars up to about 500 parsecs away, which is about ____ times the diameter of the Milky Way Galaxy.
    ___ a) 15
    ___ b) 0.15
    ___ c) .015
    ___ d) 150
    ___ e) 1.5
7. An object emits thermal (blackbody) radiation with a peak wavelength of 250nm. How does its temperature compare with the Sun?
    ___ a) 2 times hotter than the Sun
    ___ b) The temperature is the same
    ___ c) 5 times hotter than the Sun
    ___ d) 2 times colder than the Sun
    ___ e) 5 times colder than the Sun
8. The "normalized intensity" of a Sun-like star situated one parsec from Earth would be 4πI = 1. What is 4πI for a star with 100 times the Sun's energy output that is situated 10pc from Earth?
    ___ a) 10$^{-4}$
    ___ b) 1
    ___ c) 10$^{-1}$
    ___ d) 10$^{-3}$
    ___ e) 10$^{-2}$
9. An orbiting satellite makes a circular orbit 5 AU from the Sun. It measures a parallax angle of 0.2 of an arcsecond (each way from the average position). What is the star's distance?
    ___ a) 5 parsecs
    ___ b) 1 parsec
    ___ c) 25 parsecs
    ___ d) 50 parsecs
    ___ e) 10 parsecs
10. A star that is increasing it's temperature while maintaining constant luminosity is
    ___ a) in the process of dying
    ___ b) getting smaller in size
    ___ c) turning red
    ___ d) on the verge of becoming a supernovae
    ___ e)e) getting larger in size
11. The range of wavelength for visible light is between
    ___ a) 0.1 and 10 nanometers
    ___ b) 600 and 1200 nanometers
    ___ c) 5000 and 6000 nanometers
    ___ d) 400 and 700 nanometers
    ___ e) 1 and 10 nanometers
12. Based on the HR diagrams and images in stars shown in the materials, a very large red supergiant has a diameter that is about ____ greater than a small white dwarf.
    ___ a) 3x10$^7$
    ___ b) 3x10$^5$
    ___ c) 3x10$^9$
    ___ d) 3x10$^{11}$
    ___ e) 3x10$^3$
13. Why is a star made of plasma?
    ___ a) plasma is always present when there are strong magnetic fields
    ___ b) it is so hot that electrons are stripped away from the protons
    ___ c) the interstellar gas was mostly plasma
    ___ d) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body
    ___ e) plasma is generic word for "important"
14. What is the difference between a constellation and an asterism?
    ___ a) asterisms are smaller than constellations
    ___ b) asterisms are larger than constellations
    ___ c) none of these is correct
    ___ d) constellations consist of never more than ten stars.
    ___ e) constellations represent regions of the sky, like state boundaries on a map of the USA
15. Stellar parallax is
    ___ a) Two of these is correct
    ___ b) Using changes in the angular position of a star to deduce the star’s distance
    ___ c) Triangulation to deduce the distance to nearby stars
    ___ d) Using spectral lines to deduce the distance to nearby stars
    ___ e) None of these is correct.
16. Giant molecular clouds with sufficient conditions to form a star cluster would have formed them long ago. Any stellar births in the past couple of billions years probably resulted from _____ between clouds.
    ___ a) photon exchange
    ___ b) None of these is correct.
    ___ c) ion exchange
    ___ d) Two of these are correct
    ___ e) collisions
17. A starburst galaxy.
    ___ a) has only dead or dying stars
    ___ b) is a region of active stellar birth
    ___ c) Two of these are correct
    ___ d) usually is a result of collisions between galaxies
    ___ e) All of these are correct
18. Which of the following expresses Jean's criterion for the collapse of a giant molecular cloud of mass, M, radius, R, and temperature T, and pressure P? (Here ? is some constant)
    ___ a) P>?MR
    ___ b) T>?RM
    ___ c) M>?RT
    ___ d) R>?MT
    ___ e) P>?MT
19. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?
    ___ a) Two of these are correct
    ___ b) Increase mass at fixed temperature and size
    ___ c) Decrease mass at fixed temperature and size
    ___ d) Increase size at fixed pressure and mass
    ___ e) Increase temperature at fixed mass and size
20. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?
    ___ a) It is equally likely to collapse because size is not part of the Jean's criterion.
    ___ b) It is less likely to collapse because temperature can never be kept fixed
    ___ c) It is more likely to collapse because this will increase the temperature
    ___ d) It is more likely to collapse because larger things have more gravity
    ___ e) It is less likely to collapse spreading it out weakens the force of gravity
21. What is a Bok globule in the formation of stellar systems?
    ___ a) A black hole that enters a cloud and triggers the collapse
    ___ b) A cluster of giant molecular clouds that coalesce to form a solar system
    ___ c) A small portion of a giant cloud that collapses
    ___ d) A supernovae precurser that attracts more gas atoms
    ___ e) A small planet that formed before any stars have formed
22. Pre–main sequence stars are often surrounded by a protoplanetary disk and powered mainly by
    ___ a) the fission of Carbon from Helium
    ___ b) collisions between protoplanets
    ___ c) the release of gravitational energy
    ___ d) chemical reactions
    ___ e) the fusion of Helium to Carbon
23. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.
    ___ a) all of their magnetic field
    ___ b) 10% their mass
    ___ c) 1% their mass
    ___ d) 10% of their magnetic field
    ___ e) 50% their mass
24. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move
    ___ a) through a cluster as they die
    ___ b) through an HR diagram as they die
    ___ c) through an HR diagram as they are born
    ___ d) through a cluster as they are born
    ___ e) Two of these are true
    ___ a) Decreasing luminosity with no change in temperature
    ___ b) Decreasing temperature with no change in luminosity
    ___ c) Decreasing temperature and increasing luminosity
    ___ d) Increasing temperature with no change in luminosity
    ___ e) Increasing luminosity with no change in temperature
26. When a star with more than 10 solar masses ceases fuse hydrogen to helium, it
    ___ a) it fuses helium to carbon and other elements up to iron and then ceases to produce more energy
    ___ b) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.
    ___ c) it fuses helium to carbon and then ceases to produce more energy
    ___ d) ceases to convert nuclear energy.
    ___ e) it fuses helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
27. Many supernovae begin as a shock wave in the core that was caused by
    ___ a) all of these processes contribute to the shock wave
    ___ b) iron fusing into heavier elements such as uranium
    ___ c) the conversion of carbon into diamonds,
    ___ d) carbon and other elements fusing into iron
    ___ e) electrons being driven into protons to form neutrons
28. A dying star with more than 1.4 solar masses becomes a ______, and those with more than 5 solar masses becomes a _____
    ___ a) blue giant....red giant
    ___ b) white dwarf....neutron star
    ___ c) white dwarf....black hole
    ___ d) neutron star....black hole
    ___ e) white dwarf...red dwarf
29. According to Wikipedia, a star with over 20 solar masses converts its Hyrogen to Helium in about 8 billion years, but the conversion of Oxygen to heavier elements take about _____
    ___ a) 1 million years
    ___ b) 1 billion years
    ___ c) 1 thousand years
    ___ d) 1 year
    ___ e) 10 billion years
30. A grouping with 100 thousand stars would probably be a
    ___ a) elliptical galaxy
    ___ b) A-B association
    ___ c) dwarf galaxy
    ___ d) open cluster
    ___ e) globular cluster
31. A grouping with a hundred stars is probably a
    ___ a) globular cluster
    ___ b) A-B association
    ___ c) elliptical galaxy
    ___ d) dwarf galaxy
    ___ e) open cluster
32. I gravity is what holds stars in a cluster together, what is the most important process that causes them to spread apart?
    ___ a) anti-gravity
    ___ b) supernovae
    ___ c) magnetism
    ___ d) random motion
    ___ e) solar wind
33. Members of an open cluster feel significant forces only due to gravitational interaction with each other
    ___ a) True
    ___ b) False
34. Members of an open cluster feel significant forces from nearby giant molecular clouds
    ___ a) True
    ___ b) False
35. Members of a globular cluster tend to be
    ___ a) of all ages
    ___ b) old
    ___ c) young
36. Members of a globular cluster tend to have
    ___ a) a wide range of masses
    ___ b) low mass
    ___ c) high mass
37. In 1917, the astronomer Harlow Shapley was able to estimate the Sun's distance from the galactic centre using
    ___ a) goblular clusters
    ___ b) a combination of open and globular clusters
    ___ c) open clusters
38. Most globular clusters that we see in the sky orbit _____ and have ______ orbits
    ___ a) within the disk of the Milky way ... nearly circular
    ___ b) within the disk of the Milky way ... elliptic orbits
    ___ c) the center of the Milky way ... nearly circular
    ___ d) the center of the Milky way ... elliptic orbits
39. Many stars in a typical open cluster are nearly as old as the universe
    ___ a) True
    ___ b) False
40. Many stars in a typical globular cluster are nearly as old as the universe
    ___ a) True
    ___ b) False
41. The number of globular clusters in the Milky way galaxy is about
    ___ a) 15 thousand
    ___ b) 1,500
    ___ c) 15 million
    ___ d) 150
42. The location of open clusters can be described as
    ___ a) uniformly distributed within the galactic disk
    ___ b) uniformly distributed in a sphere centered at the Milky Way's center
    ___ c) between the spiral arms
    ___ d) in the spiral arms
43. Stars can "evaporate" from a cluster. What does this mean?
    ___ a) Close encounters between 3 or more cluster members gives one star enough speed to leave the cluster
    ___ b) The gravitational attraction between stars evaporates the gas from stars
    ___ c) The solar wind from neighboring stars blows the atmosphere away
44. At the center of the Crab nebula is
    ___ a)b) a pulsar
    ___ b)e) the remnants of a supernova
    ___ c)a) all of these is correct
    ___ d)d) a neutron star
    ___ e)c) none of these is correct
45. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from
    ___ a) the temperature
    ___ b) the mass as measured by Kepler's third law (modified by Newton)
    ___ c) the expansion of the universe
    ___ d) the doppler shift
    ___ e) the gravitational redshift
    ___ a) it can be associated with an "effective" temperature
    ___ b) if is not really a black body
    ___ c) it's surface can be associated with a range of temperatures
    ___ d) all of these are true
    ___ e) it is an approximate black body
47. Which of the following is NOT an essential piece of a a strong argument that a white dwarf is not only the size of the earth, but typically has the same mass as the Sun.
    ___ a) the distance to Sirius A
    ___ b) all of these are true
    ___ c) the wobble of Sirius A
    ___ d) the relative magnitude of Sirius B
    ___ e) the "color" (spectral class) of Sirius B
48. The course materials presented three arguments suggesting that a white dwarf is roughly the size of the earth. Which best summarizes them?
    ___ a) doppler-shift...period-of-pulsation...temperature-luminosity
    ___ b) temperature-luminosity...redshift...quantum-theory-of-solids
    ___ c) x-ray-emmission...doppler-shift...rotation-rate
    ___ d) all of these are true
    ___ e) HR-diagram-location...X-ray-emmision...spectral-lines
49. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,
    ___ a) 0.1%
    ___ b) 10%
    ___ c) 100%
    ___ d) 25%
    ___ e) 1%
50. What was Messier doing when he independently rediscovered the Crab in 1758?
    ___ a) Attempting to count asteroids
    ___ b) Looking for lobsters
    ___ c) Attempting one of the first star charts
    ___ d) Looking for a comet that he knew would be appearing in that part of the sky.
    ___ e) Trying to measure the orbital radius of a planet
    ___ a) The photon slows down as it goes uphill, and by c=fλ it increases wavelength therefore by E=hf, it turns red.
    ___ b) The photon slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.
    ___ c) The photon loses energy, not speed. By c=fλ , it loses frequency, and by E=hf it increases wavelength and turns red.
    ___ d) The photon slows down, by the Doppler shift, E=hf, and therefore by c=f&;lambda it turns red.
    ___ e) The photon loses energy, not speed. By E=hf, it loses frequency, and by c=fλ it increases wavelength and turns red.
52. What causes the blue glow of the Crab nebula?
    ___ a) the same emission found in a Lava lamp (ultra-violet)
    ___ b) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
    ___ c) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
    ___ d) the Doppler blue shift
    ___ e) the Gravitational blue shift
53. One way to determine the distance to a nebula or small cluster of clouds is to compare the angular expansion to the spectroscopic Doppler shift. Two clusters (A and B) have the same spectroscopically measured velocity. Cluster A is moving towards the observer and exhibits the greater angular expansion. Which cluster is closer?
    ___ a) cluster B, because it exhibits less angular expansion
    ___ b) either cluster might be more distant
    ___ c) cluster A, because it exhibits greater angular expansion
    ___ d) cluster B, because it exhibits a red Doppler shift
    ___ e) cluster A, because it exhibits a blue Doppler shift
54. What causes the "finger-like" filamentary structure in the Crab nebula?
    ___ a) cyclotron motion, causing the electrons to strike oxygen molecules
    ___ b) electrons striking hydrogen molecules, like a lava lamp
    ___ c) a light(low density) fluid underneath a heavy(high density) fluid, like a lava lamp
    ___ d) electrons striking oxygen molecules, like a lava lamp
    ___ e) a heavy (high density) fluid underneath a light (low density) fluid, like a lava lamp
55. $KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$ is the kinetic energy of a solid rotating ball, where M is mass, R is radius, and P is period. And, $power={\frac {energy}{time}}$. You are banging espressos in a little coffeehouse with your astronomy friends, talking about a new SN remnant that closely resembles the Crab. You have observed the pulsar, and wonder what the total power output of the nebula might be. You know both the period of the pulsar, as well as $\tau$, which represents the amount of time you think the pulsar will continue pulsing if it continues slowing down at its present rate. What formula do you write on your napkin?
    ___ a) $power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}$
    ___ b) $power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$
    ___ c) $power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    ___ d) $power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    ___ e) $power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}$
56. In one respect, the universie is arguably "young", considering how much complexity it contains. This is often illustrated by a calculation of
    ___ a) recalibration of supernovae luminosity
    ___ b) cosmic expansion
    ___ c) cosmic redshift
    ___ d) chimps typing Shakespeare
    ___ e) recalibration of supernovae relative magnitude
57. Comparing Hubble's original (1929) plot of redshift versus distance with the later one in 2007, the latter extends farther into space by a factor of
    ___ a) 100
    ___ b) 100,000
    ___ c) 10,000
    ___ d) 10
    ___ e) 1000
58. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used
    ___ a) Cepheid variables
    ___ b) novae
    ___ c) entire galaxies
    ___ d) supernovae
    ___ e) red giants
59. The course materials present two cosmic expansion plots. The more recent (2007) plot used
    ___ a) red giants
    ___ b) supernovae
    ___ c) Cepheid variables
    ___ d) novae
    ___ e) entire galaxies
60. Place yourself in an expanding raisinbread model of Hubble expansion. A raisin originally situated at a distance of 4 cm expands out to 12 cm. To what distance would a raisin originally situated at a distance of 2 cm expand?
    ___ a) 2
    ___ b) 6
    ___ c) 8
    ___ d) 3
    ___ e) 4
61. You at the center raisin of an expanding raisinbread model of Hubble expansion, and from your location a raisin originally situated at a distance of 1 cm expands out to a distance of 4 cm. The nearest raisin with intelligent life is situated exactly halfway between your (central) location and the edge. How would this second "intelligent" raisin view an expansion of a raisin 1 cm away?
    ___ a) expansion from 1 cm to 2 cm (half of yours)
    ___ b) expansion from 1 cm to 3 cm (since 3-1=2)
    ___ c) expansion from 1 cm to 8 cm (twice yours).
    ___ d) expansion from 1 cm to 9 cm (since 5-1=4)
    ___ e) expansion from 1 cm to 4 cm (just like yours).
62. Place yourself in an expanding raisinbread model of Hubble expansion. A raisin originally situated at a distance of 2 cm expands out to 4 cm. To what distance would a raisin originally situated at a distance of 4 cm expand?
    ___ a) 8
    ___ b) 6
    ___ c) 2
    ___ d) 3
    ___ e) 4
    ___ a) all of these are true
    ___ b) doppler shift
    ___ c) gravitational shift
    ___ d) general relativity
    ___ e) special relativity
    ___ a) Special relativity is valid only for objects travelling in a vacuum.
    ___ b) The observer on the ground would perceive the ball to be travelling faster.
    ___ c) The observer on the ground would perceive the width the train to be greater.
    ___ d) The observer on the ground would perceive the ball to be travelling more slowly.
    ___ e) The observer on the ground would perceive the width the train to be smaller.

#### Key to AstroTest4_Study-v1s1

1. Stellar parallax is
       - a) a numerical measure of brightness as seen from Earth
       + b) an annual change in angular position of a star as seen from Earth
       - c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
       - d) the total amount of energy emitted per unit time.
       - e) an astronomical object with known luminosity.
2. Luminosity is
       + a) the total amount of energy emitted per unit time.
       - b) an annual change in angular position of a star as seen from Earth
       - c) a numerical measure of brightness as seen from Earth
       - d) a numerical measure of brightness as seen from a distance of approximately 33 light-years
       - e) an astronomical object with known luminosity.
3. A standard candle is
       - a) a numerical measure of brightness as seen from a distance of approximately 33 light-years
       - b) the total amount of energy emitted per unit time.
       - c) an annual change in angular position of a star as seen from Earth
       - d) a numerical measure of brightness as seen from Earth
       + e) an astronomical object with known luminosity.
4. Absolute magnitude is
       - a) an astronomical object with known luminosity.
       - b) the total amount of energy emitted per unit time.
       + c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
       - d) an annual change in angular position of a star as seen from Earth
       - e) a numerical measure of brightness as seen from Earth
5. Relative magnitude is
       - a) the total amount of energy emitted per unit time.
       - b) a numerical measure of brightness as seen from a distance of approximately 33 light-years
       - c) an astronomical object with known luminosity.
       + d) a numerical measure of brightness as seen from Earth
       - e) an annual change in angular position of a star as seen from Earth
6. In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions allowing measurements of stellar parallax for stars up to about 500 parsecs away, which is about ____ times the diameter of the Milky Way Galaxy.
       - a) 15
       - b) 0.15
       + c) .015
       - d) 150
       - e) 1.5
7. An object emits thermal (blackbody) radiation with a peak wavelength of 250nm. How does its temperature compare with the Sun?
       + a) 2 times hotter than the Sun
       - b) The temperature is the same
       - c) 5 times hotter than the Sun
       - d) 2 times colder than the Sun
       - e) 5 times colder than the Sun
8. The "normalized intensity" of a Sun-like star situated one parsec from Earth would be 4πI = 1. What is 4πI for a star with 100 times the Sun's energy output that is situated 10pc from Earth?
       - a) 10$^{-4}$
       + b) 1
       - c) 10$^{-1}$
       - d) 10$^{-3}$
       - e) 10$^{-2}$
9. An orbiting satellite makes a circular orbit 5 AU from the Sun. It measures a parallax angle of 0.2 of an arcsecond (each way from the average position). What is the star's distance?
       - a) 5 parsecs
       - b) 1 parsec
       + c) 25 parsecs
       - d) 50 parsecs
       - e) 10 parsecs
10. A star that is increasing it's temperature while maintaining constant luminosity is
       - a) in the process of dying
       + b) getting smaller in size
       - c) turning red
       - d) on the verge of becoming a supernovae
       - e)e) getting larger in size
11. The range of wavelength for visible light is between
       - a) 0.1 and 10 nanometers
       - b) 600 and 1200 nanometers
       - c) 5000 and 6000 nanometers
       + d) 400 and 700 nanometers
       - e) 1 and 10 nanometers
12. Based on the HR diagrams and images in stars shown in the materials, a very large red supergiant has a diameter that is about ____ greater than a small white dwarf.
       - a) 3x10$^7$
       + b) 3x10$^5$
       - c) 3x10$^9$
       - d) 3x10$^{11}$
       - e) 3x10$^3$
13. Why is a star made of plasma?
       - a) plasma is always present when there are strong magnetic fields
       + b) it is so hot that electrons are stripped away from the protons
       - c) the interstellar gas was mostly plasma
       - d) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body
       - e) plasma is generic word for "important"
14. What is the difference between a constellation and an asterism?
       - a) asterisms are smaller than constellations
       - b) asterisms are larger than constellations
       - c) none of these is correct
       - d) constellations consist of never more than ten stars.
       + e) constellations represent regions of the sky, like state boundaries on a map of the USA
15. Stellar parallax is
       + a) Two of these is correct
       - b) Using changes in the angular position of a star to deduce the star’s distance
       - c) Triangulation to deduce the distance to nearby stars
       - d) Using spectral lines to deduce the distance to nearby stars
       - e) None of these is correct.
16. Giant molecular clouds with sufficient conditions to form a star cluster would have formed them long ago. Any stellar births in the past couple of billions years probably resulted from _____ between clouds.
       - a) photon exchange
       - b) None of these is correct.
       - c) ion exchange
       - d) Two of these are correct
       + e) collisions
17. A starburst galaxy.
       - a) has only dead or dying stars
       - b) is a region of active stellar birth
       + c) Two of these are correct
       - d) usually is a result of collisions between galaxies
       - e) All of these are correct
18. Which of the following expresses Jean's criterion for the collapse of a giant molecular cloud of mass, M, radius, R, and temperature T, and pressure P? (Here ? is some constant)
       - a) P>?MR
       - b) T>?RM
       + c) M>?RT
       - d) R>?MT
       - e) P>?MT
19. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?
       - a) Two of these are correct
       + b) Increase mass at fixed temperature and size
       - c) Decrease mass at fixed temperature and size
       - d) Increase size at fixed pressure and mass
       - e) Increase temperature at fixed mass and size
20. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?
       - a) It is equally likely to collapse because size is not part of the Jean's criterion.
       - b) It is less likely to collapse because temperature can never be kept fixed
       - c) It is more likely to collapse because this will increase the temperature
       - d) It is more likely to collapse because larger things have more gravity
       + e) It is less likely to collapse spreading it out weakens the force of gravity
21. What is a Bok globule in the formation of stellar systems?
       - a) A black hole that enters a cloud and triggers the collapse
       - b) A cluster of giant molecular clouds that coalesce to form a solar system
       + c) A small portion of a giant cloud that collapses
       - d) A supernovae precurser that attracts more gas atoms
       - e) A small planet that formed before any stars have formed
22. Pre–main sequence stars are often surrounded by a protoplanetary disk and powered mainly by
       - a) the fission of Carbon from Helium
       - b) collisions between protoplanets
       + c) the release of gravitational energy
       - d) chemical reactions
       - e) the fusion of Helium to Carbon
23. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.
       - a) all of their magnetic field
       - b) 10% their mass
       - c) 1% their mass
       - d) 10% of their magnetic field
       + e) 50% their mass
24. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move
       - a) through a cluster as they die
       - b) through an HR diagram as they die
       + c) through an HR diagram as they are born
       - d) through a cluster as they are born
       - e) Two of these are true
       + a) Decreasing luminosity with no change in temperature
       - b) Decreasing temperature with no change in luminosity
       - c) Decreasing temperature and increasing luminosity
       - d) Increasing temperature with no change in luminosity
       - e) Increasing luminosity with no change in temperature
26. When a star with more than 10 solar masses ceases fuse hydrogen to helium, it
       + a) it fuses helium to carbon and other elements up to iron and then ceases to produce more energy
       - b) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.
       - c) it fuses helium to carbon and then ceases to produce more energy
       - d) ceases to convert nuclear energy.
       - e) it fuses helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
27. Many supernovae begin as a shock wave in the core that was caused by
       - a) all of these processes contribute to the shock wave
       - b) iron fusing into heavier elements such as uranium
       - c) the conversion of carbon into diamonds,
       - d) carbon and other elements fusing into iron
       + e) electrons being driven into protons to form neutrons
28. A dying star with more than 1.4 solar masses becomes a ______, and those with more than 5 solar masses becomes a _____
       - a) blue giant....red giant
       - b) white dwarf....neutron star
       - c) white dwarf....black hole
       + d) neutron star....black hole
       - e) white dwarf...red dwarf
29. According to Wikipedia, a star with over 20 solar masses converts its Hyrogen to Helium in about 8 billion years, but the conversion of Oxygen to heavier elements take about _____
       - a) 1 million years
       - b) 1 billion years
       - c) 1 thousand years
       + d) 1 year
       - e) 10 billion years
30. A grouping with 100 thousand stars would probably be a
       - a) elliptical galaxy
       - b) A-B association
       - c) dwarf galaxy
       - d) open cluster
       + e) globular cluster
31. A grouping with a hundred stars is probably a
       - a) globular cluster
       - b) A-B association
       - c) elliptical galaxy
       - d) dwarf galaxy
       + e) open cluster
32. I gravity is what holds stars in a cluster together, what is the most important process that causes them to spread apart?
       - a) anti-gravity
       - b) supernovae
       - c) magnetism
       + d) random motion
       - e) solar wind
33. Members of an open cluster feel significant forces only due to gravitational interaction with each other
       - a) True
       + b) False
34. Members of an open cluster feel significant forces from nearby giant molecular clouds
       + a) True
       - b) False
35. Members of a globular cluster tend to be
       - a) of all ages
       + b) old
       - c) young
36. Members of a globular cluster tend to have
       - a) a wide range of masses
       + b) low mass
       - c) high mass
37. In 1917, the astronomer Harlow Shapley was able to estimate the Sun's distance from the galactic centre using
       + a) goblular clusters
       - b) a combination of open and globular clusters
       - c) open clusters
38. Most globular clusters that we see in the sky orbit _____ and have ______ orbits
       - a) within the disk of the Milky way ... nearly circular
       - b) within the disk of the Milky way ... elliptic orbits
       - c) the center of the Milky way ... nearly circular
       + d) the center of the Milky way ... elliptic orbits
39. Many stars in a typical open cluster are nearly as old as the universe
       - a) True
       + b) False
40. Many stars in a typical globular cluster are nearly as old as the universe
       + a) True
       - b) False
41. The number of globular clusters in the Milky way galaxy is about
       - a) 15 thousand
       - b) 1,500
       - c) 15 million
       + d) 150
42. The location of open clusters can be described as
       - a) uniformly distributed within the galactic disk
       - b) uniformly distributed in a sphere centered at the Milky Way's center
       - c) between the spiral arms
       + d) in the spiral arms
43. Stars can "evaporate" from a cluster. What does this mean?
       + a) Close encounters between 3 or more cluster members gives one star enough speed to leave the cluster
       - b) The gravitational attraction between stars evaporates the gas from stars
       - c) The solar wind from neighboring stars blows the atmosphere away
44. At the center of the Crab nebula is
       - a)b) a pulsar
       - b)e) the remnants of a supernova
       + c)a) all of these is correct
       - d)d) a neutron star
       - e)c) none of these is correct
45. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from
       - a) the temperature
       - b) the mass as measured by Kepler's third law (modified by Newton)
       - c) the expansion of the universe
       - d) the doppler shift
       + e) the gravitational redshift
       - a) it can be associated with an "effective" temperature
       - b) if is not really a black body
       - c) it's surface can be associated with a range of temperatures
       + d) all of these are true
       - e) it is an approximate black body
47. Which of the following is NOT an essential piece of a a strong argument that a white dwarf is not only the size of the earth, but typically has the same mass as the Sun.
       - a) the distance to Sirius A
       + b) all of these are true
       - c) the wobble of Sirius A
       - d) the relative magnitude of Sirius B
       - e) the "color" (spectral class) of Sirius B
48. The course materials presented three arguments suggesting that a white dwarf is roughly the size of the earth. Which best summarizes them?
       - a) doppler-shift...period-of-pulsation...temperature-luminosity
       + b) temperature-luminosity...redshift...quantum-theory-of-solids
       - c) x-ray-emmission...doppler-shift...rotation-rate
       - d) all of these are true
       - e) HR-diagram-location...X-ray-emmision...spectral-lines
49. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,
       - a) 0.1%
       - b) 10%
       - c) 100%
       + d) 25%
       - e) 1%
50. What was Messier doing when he independently rediscovered the Crab in 1758?
       - a) Attempting to count asteroids
       - b) Looking for lobsters
       - c) Attempting one of the first star charts
       + d) Looking for a comet that he knew would be appearing in that part of the sky.
       - e) Trying to measure the orbital radius of a planet
       - a) The photon slows down as it goes uphill, and by c=fλ it increases wavelength therefore by E=hf, it turns red.
       - b) The photon slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.
       - c) The photon loses energy, not speed. By c=fλ , it loses frequency, and by E=hf it increases wavelength and turns red.
       - d) The photon slows down, by the Doppler shift, E=hf, and therefore by c=f&;lambda it turns red.
       + e) The photon loses energy, not speed. By E=hf, it loses frequency, and by c=fλ it increases wavelength and turns red.
52. What causes the blue glow of the Crab nebula?
       - a) the same emission found in a Lava lamp (ultra-violet)
       - b) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
       + c) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
       - d) the Doppler blue shift
       - e) the Gravitational blue shift
53. One way to determine the distance to a nebula or small cluster of clouds is to compare the angular expansion to the spectroscopic Doppler shift. Two clusters (A and B) have the same spectroscopically measured velocity. Cluster A is moving towards the observer and exhibits the greater angular expansion. Which cluster is closer?
       - a) cluster B, because it exhibits less angular expansion
       - b) either cluster might be more distant
       + c) cluster A, because it exhibits greater angular expansion
       - d) cluster B, because it exhibits a red Doppler shift
       - e) cluster A, because it exhibits a blue Doppler shift
54. What causes the "finger-like" filamentary structure in the Crab nebula?
       - a) cyclotron motion, causing the electrons to strike oxygen molecules
       - b) electrons striking hydrogen molecules, like a lava lamp
       + c) a light(low density) fluid underneath a heavy(high density) fluid, like a lava lamp
       - d) electrons striking oxygen molecules, like a lava lamp
       - e) a heavy (high density) fluid underneath a light (low density) fluid, like a lava lamp
55. $KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$ is the kinetic energy of a solid rotating ball, where M is mass, R is radius, and P is period. And, $power={\frac {energy}{time}}$. You are banging espressos in a little coffeehouse with your astronomy friends, talking about a new SN remnant that closely resembles the Crab. You have observed the pulsar, and wonder what the total power output of the nebula might be. You know both the period of the pulsar, as well as $\tau$, which represents the amount of time you think the pulsar will continue pulsing if it continues slowing down at its present rate. What formula do you write on your napkin?
       + a) $power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}$
       - b) $power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$
       - c) $power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}$
       - d) $power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}$
       - e) $power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}$
56. In one respect, the universie is arguably "young", considering how much complexity it contains. This is often illustrated by a calculation of
       - a) recalibration of supernovae luminosity
       - b) cosmic expansion
       - c) cosmic redshift
       + d) chimps typing Shakespeare
       - e) recalibration of supernovae relative magnitude
57. Comparing Hubble's original (1929) plot of redshift versus distance with the later one in 2007, the latter extends farther into space by a factor of
       - a) 100
       - b) 100,000
       - c) 10,000
       + d) 10
       - e) 1000
58. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used
       - a) Cepheid variables
       - b) novae
       + c) entire galaxies
       - d) supernovae
       - e) red giants
59. The course materials present two cosmic expansion plots. The more recent (2007) plot used
       - a) red giants
       + b) supernovae
       - c) Cepheid variables
       - d) novae
       - e) entire galaxies
60. Place yourself in an expanding raisinbread model of Hubble expansion. A raisin originally situated at a distance of 4 cm expands out to 12 cm. To what distance would a raisin originally situated at a distance of 2 cm expand?
       - a) 2
       + b) 6
       - c) 8
       - d) 3
       - e) 4
61. You at the center raisin of an expanding raisinbread model of Hubble expansion, and from your location a raisin originally situated at a distance of 1 cm expands out to a distance of 4 cm. The nearest raisin with intelligent life is situated exactly halfway between your (central) location and the edge. How would this second "intelligent" raisin view an expansion of a raisin 1 cm away?
       - a) expansion from 1 cm to 2 cm (half of yours)
       - b) expansion from 1 cm to 3 cm (since 3-1=2)
       - c) expansion from 1 cm to 8 cm (twice yours).
       - d) expansion from 1 cm to 9 cm (since 5-1=4)
       + e) expansion from 1 cm to 4 cm (just like yours).
62. Place yourself in an expanding raisinbread model of Hubble expansion. A raisin originally situated at a distance of 2 cm expands out to 4 cm. To what distance would a raisin originally situated at a distance of 4 cm expand?
       + a) 8
       - b) 6
       - c) 2
       - d) 3
       - e) 4
       - a) all of these are true
       - b) doppler shift
       - c) gravitational shift
       - d) general relativity
       + e) special relativity
       - a) Special relativity is valid only for objects travelling in a vacuum.
       + b) The observer on the ground would perceive the ball to be travelling faster.
       - c) The observer on the ground would perceive the width the train to be greater.
       - d) The observer on the ground would perceive the ball to be travelling more slowly.
       - e) The observer on the ground would perceive the width the train to be smaller.

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    http://en.wikiversity.org/w/index.php?title=Astronomy_college_course/Star_cluster_quiz&oldid=1388988
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   ##### Study guide

    https://en.wikiversity.org/w/index.php?title=Astronomy_college_course&oldid=1388890
    http://en.wikiversity.org/w/index.php?title=Astronomy_college_course/Star_(Wikipedia)&oldid=1218705
    http://en.wikipedia.org/w/index.php?title=Star_cluster&oldid=662839103
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