# 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

This spectrum of the star Vega suggests that
___ 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.

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, 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

21. 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) 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

This spectrum of the star Vega suggests that
- 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.

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, 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

21. 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) 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.