# Astronomy college course/Sizes of white dwarfs, neutron stars, quasars/questions
## AstroSizeWhitdwrfNeutstarQSO_Study

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### AstroSizeWhitdwrfNeutstarQSO_Study-v1s1

1. At the center of the Crab nebula is
    ___ a)e) the remnants of a supernova
    ___ b)a) all of these is correct
    ___ c)c) none of these is correct
    ___ d)d) a neutron star
    ___ e)b) a pulsar
2. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from
    ___ a) the doppler shift
    ___ b) the expansion of the universe
    ___ c) the mass as measured by Kepler's third law (modified by Newton)
    ___ d) the gravitational redshift
    ___ e) the temperature
    ___ a) it's surface can be associated with a range of temperatures
    ___ b) it can be associated with an "effective" temperature
    ___ c) it is an approximate black body
    ___ d) all of these are true
    ___ e) if is not really a black body
4. 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 relative magnitude of Sirius B
    ___ b) all of these are true
    ___ c) the "color" (spectral class) of Sirius B
    ___ d) the wobble of Sirius A
    ___ e) the distance to Sirius A
5. The course materials presented three arguments suggesting that a white dwarf is roughly the size of the earth. Which best summarizes them?
    ___ a) temperature-luminosity...redshift...quantum-theory-of-solids
    ___ b) all of these are true
    ___ c) x-ray-emmission...doppler-shift...rotation-rate
    ___ d) HR-diagram-location...X-ray-emmision...spectral-lines
    ___ e) doppler-shift...period-of-pulsation...temperature-luminosity
6. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,
    ___ a) 25%
    ___ b) 100%
    ___ c) 1%
    ___ d) 10%
    ___ e) 0.1%
7. What was Messier doing when he independently rediscovered the Crab in 1758?
    ___ a) Looking for lobsters
    ___ 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 a comet that he knew would be appearing in that part of the sky.
    ___ 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, by the Doppler shift, E=hf, and therefore by c=f&;lambda it turns red.
    ___ c) The photon slows down as it goes uphill, and by c=fλ it increases wavelength therefore by E=hf, it turns red.
    ___ d) The photon slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.
    ___ e) The photon loses energy, not speed. By c=fλ , it loses frequency, and by E=hf it increases wavelength and turns red.
9. What causes the blue glow of the Crab nebula?
    ___ a) the Gravitational blue shift
    ___ b) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
    ___ c) the Doppler blue shift
    ___ d) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
    ___ e) the same emission found in a Lava lamp (ultra-violet)
10. 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 A, because it exhibits greater angular expansion
    ___ b) cluster A, because it exhibits a blue Doppler shift
    ___ c) cluster B, because it exhibits a red Doppler shift
    ___ d) cluster B, because it exhibits less angular expansion
    ___ e) either cluster might be more distant
11. What causes the "finger-like" filamentary structure in the Crab nebula?
    ___ a) electrons striking hydrogen molecules, like a lava lamp
    ___ b) a heavy (high density) fluid underneath a light (low density) fluid, 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) cyclotron motion, causing the electrons to strike oxygen molecules
12. $KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$ 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) $power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    ___ c) $power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}$
    ___ d) $power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    ___ e) $power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$
13. In one respect, the universie is arguably "young", considering how much complexity it contains. This is often illustrated by a calculation of
    ___ a) cosmic redshift
    ___ b) recalibration of supernovae relative magnitude
    ___ c) recalibration of supernovae luminosity
    ___ d) chimps typing Shakespeare
    ___ e) cosmic expansion
14. 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) 1000
    ___ b) 10
    ___ c) 10,000
    ___ d) 100,000
    ___ e) 100
15. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used
    ___ a) entire galaxies
    ___ b) Cepheid variables
    ___ c) novae
    ___ d) supernovae
    ___ e) red giants
16. The course materials present two cosmic expansion plots. The more recent (2007) plot used
    ___ a) supernovae
    ___ b) red giants
    ___ c) novae
    ___ d) Cepheid variables
    ___ e) entire galaxies
17. 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) 8
    ___ c) 2
    ___ d) 3
    ___ e) 4
18. 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 9 cm (since 5-1=4)
    ___ c) expansion from 1 cm to 8 cm (twice yours).
    ___ d) expansion from 1 cm to 3 cm (since 3-1=2)
    ___ e) expansion from 1 cm to 4 cm (just like yours).
19. 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) 4
    ___ b) 8
    ___ c) 3
    ___ d) 6
    ___ e) 2
    ___ a) general relativity
    ___ b) all of these are true
    ___ c) doppler shift
    ___ d) gravitational shift
    ___ e) special relativity
    ___ a) The observer on the ground would perceive the width the train to be greater.
    ___ b) Special relativity is valid only for objects travelling in a vacuum.
    ___ c) The observer on the ground would perceive the ball to be travelling faster.
    ___ 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 AstroSizeWhitdwrfNeutstarQSO_Study-v1s1

1. At the center of the Crab nebula is
    - a)e) the remnants of a supernova
    + b)a) all of these is correct
    - c)c) none of these is correct
    - d)d) a neutron star
    - e)b) a pulsar
2. Aside from its location on the HR diagram, evidence that the white dwarf has a small radius can be found from
    - a) the doppler shift
    - b) the expansion of the universe
    - c) the mass as measured by Kepler's third law (modified by Newton)
    + d) the gravitational redshift
    - e) the temperature
    - a) it's surface can be associated with a range of temperatures
    - b) it can be associated with an "effective" temperature
    - c) it is an approximate black body
    + d) all of these are true
    - e) if is not really a black body
4. 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 relative magnitude of Sirius B
    + b) all of these are true
    - c) the "color" (spectral class) of Sirius B
    - d) the wobble of Sirius A
    - e) the distance to Sirius A
5. The course materials presented three arguments suggesting that a white dwarf is roughly the size of the earth. Which best summarizes them?
    + a) temperature-luminosity...redshift...quantum-theory-of-solids
    - b) all of these are true
    - c) x-ray-emmission...doppler-shift...rotation-rate
    - d) HR-diagram-location...X-ray-emmision...spectral-lines
    - e) doppler-shift...period-of-pulsation...temperature-luminosity
6. As of 2008, the percent uncertainty in the distance to the Crab nebula is approximately,
    + a) 25%
    - b) 100%
    - c) 1%
    - d) 10%
    - e) 0.1%
7. What was Messier doing when he independently rediscovered the Crab in 1758?
    - a) Looking for lobsters
    - 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 a comet that he knew would be appearing in that part of the sky.
    + 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, by the Doppler shift, E=hf, and therefore by c=f&;lambda it turns red.
    - c) The photon slows down as it goes uphill, and by c=fλ it increases wavelength therefore by E=hf, it turns red.
    - d) The photon slows down, by the Doppler shift, c=fλ, and therefore by E=hf it turns red.
    - e) The photon loses energy, not speed. By c=fλ , it loses frequency, and by E=hf it increases wavelength and turns red.
9. What causes the blue glow of the Crab nebula?
    - a) the Gravitational blue shift
    + b) the curving motion of electrons in a magnetic field; such motion resembles a radio antenna
    - c) the Doppler blue shift
    - d) the curving motion of electrons in a magnetic field; such motion traps ultra-violet and blue light
    - e) the same emission found in a Lava lamp (ultra-violet)
10. 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 A, because it exhibits greater angular expansion
    - b) cluster A, because it exhibits a blue Doppler shift
    - c) cluster B, because it exhibits a red Doppler shift
    - d) cluster B, because it exhibits less angular expansion
    - e) either cluster might be more distant
11. What causes the "finger-like" filamentary structure in the Crab nebula?
    - a) electrons striking hydrogen molecules, like a lava lamp
    - b) a heavy (high density) fluid underneath a light (low density) fluid, 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) cyclotron motion, causing the electrons to strike oxygen molecules
12. $KE={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$ 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) $power={\frac {4\pi ^{2}}{5\tau ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    - c) $power={\frac {4\pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}\tau ^{4}$
    - d) $power={\frac {5}{4\tau \pi ^{2}}}{\frac {MR^{2}}{P^{2}}}$
    - e) $power={\frac {4\tau \pi ^{2}}{5}}{\frac {MR^{2}}{P^{2}}}$
13. In one respect, the universie is arguably "young", considering how much complexity it contains. This is often illustrated by a calculation of
    - a) cosmic redshift
    - b) recalibration of supernovae relative magnitude
    - c) recalibration of supernovae luminosity
    + d) chimps typing Shakespeare
    - e) cosmic expansion
14. 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) 1000
    + b) 10
    - c) 10,000
    - d) 100,000
    - e) 100
15. The course materials present two cosmic expansion plots. Hubble's original (1929) plot used
    + a) entire galaxies
    - b) Cepheid variables
    - c) novae
    - d) supernovae
    - e) red giants
16. The course materials present two cosmic expansion plots. The more recent (2007) plot used
    + a) supernovae
    - b) red giants
    - c) novae
    - d) Cepheid variables
    - e) entire galaxies
17. 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) 8
    - c) 2
    - d) 3
    - e) 4
18. 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 9 cm (since 5-1=4)
    - c) expansion from 1 cm to 8 cm (twice yours).
    - d) expansion from 1 cm to 3 cm (since 3-1=2)
    + e) expansion from 1 cm to 4 cm (just like yours).
19. 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) 4
    + b) 8
    - c) 3
    - d) 6
    - e) 2
    - a) general relativity
    - b) all of these are true
    - c) doppler shift
    - d) gravitational shift
    + e) special relativity
    - a) The observer on the ground would perceive the width the train to be greater.
    - b) Special relativity is valid only for objects travelling in a vacuum.
    + c) The observer on the ground would perceive the ball to be travelling faster.
    - 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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   ##### Study guide

    https://en.wikiversity.org/w/index.php?title=Astronomy_college_course/Sizes_of_white_dwarfs,_neutron_stars,_quasars&oldid=1286949