# OpenStax Astronomy/Test 4 Study guide

## Astronomy midterm Test 4 Study Guide

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### Astronomy midterm Test 4 Study Guide-v1s1

1. Stellar parallax 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.

2. Luminosity 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) the total amount of energy emitted per unit time.
___ d) an astronomical object with known luminosity.
___ e) a numerical measure of brightness as seen from a distance of approximately 33 light-years

3. A standard candle is

___ a) an annual change in angular position of a star as seen from Earth
___ b) an astronomical object with known luminosity.
___ c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
___ d) a numerical measure of brightness as seen from Earth
___ e) the total amount of energy emitted per unit time.

4. Absolute 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) a numerical measure of brightness as seen from Earth
___ d) an annual change in angular position of a star as seen from Earth
___ e) an astronomical object with known luminosity.

5. Relative magnitude is

___ a) an annual change in angular position of a star as seen from Earth
___ 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) the total amount of energy emitted per unit time.

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) 1.5
___ b) 0.15
___ c) 150
___ d) 15
___ e) .015

7. An object emits thermal (blackbody) radiation with a peak wavelength of 250nm. How does its temperature compare with the Sun?

___ a) 2 times colder than the Sun
___ b) The temperature is the same
___ c) 2 times hotter than the Sun
___ d) 5 times hotter 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) 10-2
___ c) 1
___ d) 10-3
___ e) 10-1

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) 25 parsecs
___ b) 10 parsecs
___ c) 5 parsecs
___ d) 1 parsec
___ e) 50 parsecs

10. A star that is increasing it's temperature while maintaining constant luminosity is

___ a) in the process of dying
___ b) turning red
___ c) getting smaller in size
___ 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) 400 and 700 nanometers
___ b) 0.1 and 10 nanometers
___ c) 600 and 1200 nanometers
___ d) 1 and 10 nanometers
___ e) 5000 and 6000 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) 3x103
___ b) 3x105
___ c) 3x1011
___ d) 3x109
___ e) 3x107

13. Why is a star made of plasma?

___ a) the interstellar gas was mostly plasma
___ b) plasma is generic word for "important"
___ c) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body
___ d) it is so hot that electrons are stripped away from the protons
___ e) plasma is always present when there are strong magnetic fields

14. What is the difference between a constellation and an asterism?

___ a) none of these is correct
___ b) constellations represent regions of the sky, like state boundaries on a map of the USA
___ c) constellations consist of never more than ten stars.
___ d) asterisms are smaller than constellations
___ e) asterisms are larger than constellations

15. Stellar parallax is

___ a) Using changes in the angular position of a star to deduce the star’s distance
___ b) Using spectral lines to deduce the distance to nearby stars
___ c) Triangulation to deduce the distance to nearby stars
___ d) None of these is correct.
___ e) Two 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) Two of these are correct
___ b) collisions
___ c) photon exchange
___ d) ion exchange
___ e) None of these is correct.

17. A starburst galaxy.

___ a) is a region of active stellar birth
___ b) Two of these are correct
___ c) usually is a result of collisions between galaxies
___ d) All of these are correct
___ e) has only dead or dying stars

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) P>?MT
___ c) R>?MT
___ d) M>?RT
___ e) T>?RM

19. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?

___ a) Decrease mass at fixed temperature and size
___ b) Two of these are correct
___ c) Increase temperature at fixed mass and size
___ d) Increase mass at fixed temperature and size
___ e) Increase size at fixed pressure and mass

20. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?

___ a) It is more likely to collapse because larger things have more gravity
___ b) It is equally likely to collapse because size is not part of the Jean's criterion.
___ c) It is more likely to collapse because this will increase the temperature
___ d) It is less likely to collapse because temperature can never be kept fixed
___ 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 supernovae precurser that attracts more gas atoms
___ b) A black hole that enters a cloud and triggers the collapse
___ c) A cluster of giant molecular clouds that coalesce to form a solar system
___ d) A small portion of a giant cloud that collapses
___ 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) collisions between protoplanets
___ b) chemical reactions
___ c) the release of gravitational energy
___ d) the fusion of Helium to Carbon
___ e) the fission of Carbon from Helium

23. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.

___ a) 1% their mass
___ b) 50% their mass
___ c) all of their magnetic field
___ d) 10% their mass
___ e) 10% of their magnetic field

24. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move

___ a) through a cluster as they are born
___ b) through an HR diagram as they are born
___ c) Two of these are true
___ d) through a cluster as they die
___ e) through an HR diagram as they die

25. How do low-mass stars change as they are born?
Birth of stars HR path tracks
___ a) Increasing luminosity with no change in temperature
___ b) Decreasing luminosity with no change in temperature
___ c) Increasing temperature with no change in luminosity
___ d) Decreasing temperature and increasing luminosity
___ e) Decreasing temperature with no change in luminosity

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 helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
___ c) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.
___ d) it fuses helium to carbon and then ceases to produce more energy
___ e) ceases to convert nuclear energy.

27. Many supernovae begin as a shock wave in the core that was caused by

___ a) carbon and other elements fusing into iron
___ b) the conversion of carbon into diamonds,
___ c) all of these processes contribute to the shock wave
___ d) iron fusing into heavier elements such as uranium
___ 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) white dwarf...red dwarf
___ b) blue giant....red giant
___ c) white dwarf....neutron star
___ d) neutron star....black hole
___ e) white dwarf....black hole

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 thousand years
___ b) 1 year
___ c) 10 billion years
___ d) 1 million years
___ e) 1 billion years

30. A grouping with 100 thousand stars would probably be a

___ a) elliptical galaxy
___ b) dwarf galaxy
___ c) open cluster
___ d) globular cluster
___ e) A-B association

31. A grouping with a hundred stars is probably a

___ a) globular cluster
___ b) dwarf galaxy
___ c) open cluster
___ d) A-B association
___ e) elliptical galaxy

32. I gravity is what holds stars in a cluster together, what is the most important process that causes them to spread apart?

___ a) random motion
___ b) anti-gravity
___ c) magnetism
___ d) supernovae
___ 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) low mass
___ b) high mass
___ c) a wide range of masses

37. In 1917, the astronomer Harlow Shapley was able to estimate the Sun's distance from the galactic centre using

___ a) open clusters
___ b) goblular clusters
___ c) a combination of open and globular 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) 150
___ b) 15 thousand
___ c) 15 million
___ d) 1,500

42. The location of open clusters can be described as

___ a) in the spiral arms
___ b) uniformly distributed within the galactic disk
___ c) between the spiral arms
___ d) uniformly distributed in a sphere centered at the Milky Way's center

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 solar wind from neighboring stars blows the atmosphere away
___ c) The gravitational attraction between stars evaporates the gas from stars

44. At the center of the Crab nebula is

___ a)b) a pulsar
___ b)d) a neutron star
___ c)a) all of these is correct
___ d)c) none of these is correct
___ e)e) the remnants of a supernova

45. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from

___ a) the mass as measured by Kepler's third law (modified by Newton)
___ b) the temperature
___ c) the expansion of the universe
___ d) the doppler shift
___ e) the gravitational redshift

46.

This spectrum of the star Vega suggests that
___ a) all of these are true
___ b) it can be associated with an "effective" temperature
___ c) it's surface can be associated with a range of temperatures
___ d) if is not really a black body
___ 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) the relative magnitude of Sirius B
___ c) the "color" (spectral class) of Sirius B
___ d) all of these are true
___ e) the wobble of Sirius A

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) HR-diagram-location...X-ray-emmision...spectral-lines
___ c) all of these are true
___ d) temperature-luminosity...redshift...quantum-theory-of-solids
___ e) x-ray-emmission...doppler-shift...rotation-rate

49. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,

___ a) 10%
___ b) 25%
___ c) 1%
___ d) 100%
___ e) 0.1%

50. What was Messier doing when he independently rediscovered the Crab in 1758?

___ a) Looking for a comet that he knew would be appearing in that part of the sky.
___ b) Trying to measure the orbital radius of a planet
___ c) Attempting to count asteroids
___ d) Attempting one of the first star charts
___ e) Looking for lobsters

51.

What best explains this figure?
___ a) The photon loses energy, not speed. By E=hf, it loses frequency, and by c=fλ it increases wavelength and turns red.
___ b) The photon slows down as it goes uphill, and by c=fλ it increases wavelength 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 slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.

52. What causes the blue glow of the Crab nebula?

___ a) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
___ b) the same emission found in a Lava lamp (ultra-violet)
___ c) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
___ d) the Gravitational blue shift
___ e) the Doppler 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) cluster B, because it exhibits a red Doppler shift
___ c) either cluster might be more distant
___ d) cluster A, because it exhibits a blue Doppler shift
___ e) cluster A, because it exhibits greater angular expansion

54. What causes the "finger-like" filamentary structure in the Crab nebula?

___ a) electrons striking oxygen molecules, like a lava lamp
___ b) a light(low density) fluid underneath a heavy(high density) fluid, like a lava lamp
___ c) electrons striking hydrogen molecules, like a lava lamp
___ d) cyclotron motion, causing the electrons to strike oxygen molecules
___ 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) ${\displaystyle power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}}$
___ 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) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}}$
___ e) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}}$

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 relative magnitude
___ b) cosmic expansion
___ c) recalibration of supernovae luminosity
___ d) cosmic redshift
___ e) chimps typing Shakespeare

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) 1000
___ c) 100,000
___ d) 10,000
___ e) 10

58. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used

___ a) entire galaxies
___ b) novae
___ c) red giants
___ d) supernovae
___ e) Cepheid variables

59. The course materials present two cosmic expansion plots. The more recent (2007) plot used

___ a) novae
___ b) supernovae
___ c) Cepheid variables
___ d) red giants
___ 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) 6
___ b) 4
___ c) 3
___ d) 2
___ e) 8

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 8 cm (twice yours).
___ b) expansion from 1 cm to 2 cm (half of yours)
___ c) expansion from 1 cm to 4 cm (just like yours).
___ d) expansion from 1 cm to 9 cm (since 5-1=4)
___ e) expansion from 1 cm to 3 cm (since 3-1=2)

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) 6
___ b) 4
___ c) 8
___ d) 3
___ e) 2

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

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 width the train to be smaller.
___ 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 faster.
___ e) The observer on the ground would perceive the ball to be travelling more slowly.

#### Key to Astronomy midterm Test 4 Study Guide-v1s1

1. Stellar parallax 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.

2. Luminosity 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) the total amount of energy emitted per unit time.
- d) an astronomical object with known luminosity.
- e) a numerical measure of brightness as seen from a distance of approximately 33 light-years

3. A standard candle is

- a) an annual change in angular position of a star as seen from Earth
+ b) an astronomical object with known luminosity.
- c) a numerical measure of brightness as seen from a distance of approximately 33 light-years
- d) a numerical measure of brightness as seen from Earth
- e) the total amount of energy emitted per unit time.

4. Absolute 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) a numerical measure of brightness as seen from Earth
- d) an annual change in angular position of a star as seen from Earth
- e) an astronomical object with known luminosity.

5. Relative magnitude is

- a) an annual change in angular position of a star as seen from Earth
- 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) the total amount of energy emitted per unit time.

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) 1.5
- b) 0.15
- c) 150
- d) 15
+ e) .015

7. An object emits thermal (blackbody) radiation with a peak wavelength of 250nm. How does its temperature compare with the Sun?

- a) 2 times colder than the Sun
- b) The temperature is the same
+ c) 2 times hotter than the Sun
- d) 5 times hotter 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) 10-2
+ c) 1
- d) 10-3
- e) 10-1

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) 25 parsecs
- b) 10 parsecs
- c) 5 parsecs
- d) 1 parsec
- e) 50 parsecs

10. A star that is increasing it's temperature while maintaining constant luminosity is

- a) in the process of dying
- b) turning red
+ c) getting smaller in size
- 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) 400 and 700 nanometers
- b) 0.1 and 10 nanometers
- c) 600 and 1200 nanometers
- d) 1 and 10 nanometers
- e) 5000 and 6000 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) 3x103
+ b) 3x105
- c) 3x1011
- d) 3x109
- e) 3x107

13. Why is a star made of plasma?

- a) the interstellar gas was mostly plasma
- b) plasma is generic word for "important"
- c) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body
+ d) it is so hot that electrons are stripped away from the protons
- e) plasma is always present when there are strong magnetic fields

14. What is the difference between a constellation and an asterism?

- a) none of these is correct
+ b) constellations represent regions of the sky, like state boundaries on a map of the USA
- c) constellations consist of never more than ten stars.
- d) asterisms are smaller than constellations
- e) asterisms are larger than constellations

15. Stellar parallax is

- a) Using changes in the angular position of a star to deduce the star’s distance
- b) Using spectral lines to deduce the distance to nearby stars
- c) Triangulation to deduce the distance to nearby stars
- d) None of these is correct.
+ e) Two 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) Two of these are correct
+ b) collisions
- c) photon exchange
- d) ion exchange
- e) None of these is correct.

17. A starburst galaxy.

- a) is a region of active stellar birth
+ b) Two of these are correct
- c) usually is a result of collisions between galaxies
- d) All of these are correct
- e) has only dead or dying stars

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) P>?MT
- c) R>?MT
+ d) M>?RT
- e) T>?RM

19. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?

- a) Decrease mass at fixed temperature and size
- b) Two of these are correct
- c) Increase temperature at fixed mass and size
+ d) Increase mass at fixed temperature and size
- e) Increase size at fixed pressure and mass

20. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?

- a) It is more likely to collapse because larger things have more gravity
- b) It is equally likely to collapse because size is not part of the Jean's criterion.
- c) It is more likely to collapse because this will increase the temperature
- d) It is less likely to collapse because temperature can never be kept fixed
+ 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 supernovae precurser that attracts more gas atoms
- b) A black hole that enters a cloud and triggers the collapse
- c) A cluster of giant molecular clouds that coalesce to form a solar system
+ d) A small portion of a giant cloud that collapses
- 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) collisions between protoplanets
- b) chemical reactions
+ c) the release of gravitational energy
- d) the fusion of Helium to Carbon
- e) the fission of Carbon from Helium

23. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.

- a) 1% their mass
+ b) 50% their mass
- c) all of their magnetic field
- d) 10% their mass
- e) 10% of their magnetic field

24. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move

- a) through a cluster as they are born
+ b) through an HR diagram as they are born
- c) Two of these are true
- d) through a cluster as they die
- e) through an HR diagram as they die

25. How do low-mass stars change as they are born?
Birth of stars HR path tracks
- a) Increasing luminosity with no change in temperature
+ b) Decreasing luminosity with no change in temperature
- c) Increasing temperature with no change in luminosity
- d) Decreasing temperature and increasing luminosity
- e) Decreasing temperature with no change in luminosity

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 helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
- c) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.
- d) it fuses helium to carbon and then ceases to produce more energy
- e) ceases to convert nuclear energy.

27. Many supernovae begin as a shock wave in the core that was caused by

- a) carbon and other elements fusing into iron
- b) the conversion of carbon into diamonds,
- c) all of these processes contribute to the shock wave
- d) iron fusing into heavier elements such as uranium
+ 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) white dwarf...red dwarf
- b) blue giant....red giant
- c) white dwarf....neutron star
+ d) neutron star....black hole
- e) white dwarf....black hole

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 thousand years
+ b) 1 year
- c) 10 billion years
- d) 1 million years
- e) 1 billion years

30. A grouping with 100 thousand stars would probably be a

- a) elliptical galaxy
- b) dwarf galaxy
- c) open cluster
+ d) globular cluster
- e) A-B association

31. A grouping with a hundred stars is probably a

- a) globular cluster
- b) dwarf galaxy
+ c) open cluster
- d) A-B association
- e) elliptical galaxy

32. I gravity is what holds stars in a cluster together, what is the most important process that causes them to spread apart?

+ a) random motion
- b) anti-gravity
- c) magnetism
- d) supernovae
- 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) low mass
- b) high mass
- c) a wide range of masses

37. In 1917, the astronomer Harlow Shapley was able to estimate the Sun's distance from the galactic centre using

- a) open clusters
+ b) goblular clusters
- c) a combination of open and globular 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) 150
- b) 15 thousand
- c) 15 million
- d) 1,500

42. The location of open clusters can be described as

+ a) in the spiral arms
- b) uniformly distributed within the galactic disk
- c) between the spiral arms
- d) uniformly distributed in a sphere centered at the Milky Way's center

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 solar wind from neighboring stars blows the atmosphere away
- c) The gravitational attraction between stars evaporates the gas from stars

44. At the center of the Crab nebula is

- a)b) a pulsar
- b)d) a neutron star
+ c)a) all of these is correct
- d)c) none of these is correct
- e)e) the remnants of a supernova

45. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from

- a) the mass as measured by Kepler's third law (modified by Newton)
- b) the temperature
- c) the expansion of the universe
- d) the doppler shift
+ e) the gravitational redshift

46.

This spectrum of the star Vega suggests that
+ a) all of these are true
- b) it can be associated with an "effective" temperature
- c) it's surface can be associated with a range of temperatures
- d) if is not really a black body
- 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) the relative magnitude of Sirius B
- c) the "color" (spectral class) of Sirius B
+ d) all of these are true
- e) the wobble of Sirius A

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) HR-diagram-location...X-ray-emmision...spectral-lines
- c) all of these are true
+ d) temperature-luminosity...redshift...quantum-theory-of-solids
- e) x-ray-emmission...doppler-shift...rotation-rate

49. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,

- a) 10%
+ b) 25%
- c) 1%
- d) 100%
- e) 0.1%

50. What was Messier doing when he independently rediscovered the Crab in 1758?

+ a) Looking for a comet that he knew would be appearing in that part of the sky.
- b) Trying to measure the orbital radius of a planet
- c) Attempting to count asteroids
- d) Attempting one of the first star charts
- e) Looking for lobsters

51.

What best explains this figure?
+ a) The photon loses energy, not speed. By E=hf, it loses frequency, and by c=fλ it increases wavelength and turns red.
- b) The photon slows down as it goes uphill, and by c=fλ it increases wavelength 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 slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.

52. What causes the blue glow of the Crab nebula?

+ a) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
- b) the same emission found in a Lava lamp (ultra-violet)
- c) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
- d) the Gravitational blue shift
- e) the Doppler 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) cluster B, because it exhibits a red Doppler shift
- c) either cluster might be more distant
- d) cluster A, because it exhibits a blue Doppler shift
+ e) cluster A, because it exhibits greater angular expansion

54. What causes the "finger-like" filamentary structure in the Crab nebula?

- a) electrons striking oxygen molecules, like a lava lamp
+ b) a light(low density) fluid underneath a heavy(high density) fluid, like a lava lamp
- c) electrons striking hydrogen molecules, like a lava lamp
- d) cyclotron motion, causing the electrons to strike oxygen molecules
- 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) ${\displaystyle power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}}$
- 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) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau }}{\frac {MR^{2}}{P^{2}}}}$
- e) ${\displaystyle power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}}$

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 relative magnitude
- b) cosmic expansion
- c) recalibration of supernovae luminosity
- d) cosmic redshift
+ e) chimps typing Shakespeare

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) 1000
- c) 100,000
- d) 10,000
+ e) 10

58. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used

+ a) entire galaxies
- b) novae
- c) red giants
- d) supernovae
- e) Cepheid variables

59. The course materials present two cosmic expansion plots. The more recent (2007) plot used

- a) novae
+ b) supernovae
- c) Cepheid variables
- d) red giants
- 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) 6
- b) 4
- c) 3
- d) 2
- e) 8

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 8 cm (twice yours).
- b) expansion from 1 cm to 2 cm (half of yours)
+ c) expansion from 1 cm to 4 cm (just like yours).
- d) expansion from 1 cm to 9 cm (since 5-1=4)
- e) expansion from 1 cm to 3 cm (since 3-1=2)

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) 6
- b) 4
+ c) 8
- d) 3
- e) 2

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

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 width the train to be smaller.
- 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 faster.
- e) The observer on the ground would perceive the ball to be travelling more slowly.