# Astronomy college course/Unit 4 study guide

## 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) 3x107
___ b) 3x105
___ c) 3x109
___ d) 3x1011
___ e) 3x103

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

25. How do low-mass stars change as they are born?
Birth of stars HR path tracks
___ 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

46.

This spectrum of the star Vega suggests that
___ 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

51.

What best explains this figure?
___ 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. ${\displaystyle KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}}$ is the kinetic energy of a solid rotating ball, where M is mass, R is radius, and P is period. And, ${\displaystyle power={\frac {energy}{time}}}$.
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 ${\displaystyle \tau }$, 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) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}}$
___ b) ${\displaystyle power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}}$
___ c) ${\displaystyle power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}}$
___ d) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}}$
___ e) ${\displaystyle power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}}$

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

63.
This light clock is associated with
___ a) all of these are true
___ b) doppler shift
___ c) gravitational shift
___ d) general relativity
___ e) special relativity

64.
Suppose the light clock involved a ball being tossed back and forth on a train going just under the speed of sound. In contrast to the situation for light reflecting back and forth on a train going just under the speed of light, there is virtually no time dilation. Why?
___ 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) 3x107
+ b) 3x105
- c) 3x109
- d) 3x1011
- e) 3x103

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

25. How do low-mass stars change as they are born?
Birth of stars HR path tracks
+ 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

46.

This spectrum of the star Vega suggests that
- 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

51.

What best explains this figure?
- 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. ${\displaystyle KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}}$ is the kinetic energy of a solid rotating ball, where M is mass, R is radius, and P is period. And, ${\displaystyle power={\frac {energy}{time}}}$.
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 ${\displaystyle \tau }$, 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) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}}$
- b) ${\displaystyle power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}}$
- c) ${\displaystyle power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}}$
- d) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}}$
- e) ${\displaystyle power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}}$

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

63.
This light clock is associated with
- a) all of these are true
- b) doppler shift
- c) gravitational shift
- d) general relativity
+ e) special relativity

64.
Suppose the light clock involved a ball being tossed back and forth on a train going just under the speed of sound. In contrast to the situation for light reflecting back and forth on a train going just under the speed of light, there is virtually no time dilation. Why?
- 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.