Question 1

Convection that reaches from the core to the surface of a star is important in each of the following EXCEPT ONE. Which is the exception?

Accepted Answer

A) main-sequence stars of one solar mass 
B) red dwarfs 
C) giant stars 
D) carbon stars 
A) main-sequence stars of one solar mass 
B) red dwarfs 
C) giant stars 
D) carbon stars

Question 2

A planetary nebula is:

Accepted Answer

A) a contracting spherical cloud of gas surrounding a newly formed star, in which planets are forming. 
B) the expanding nebula formed by the supernova explosion of a massive star. 
C) an expanding gas shell surrounding a hot, white dwarf star. 
D) a disk-shaped nebula of dust and gas from which planets will eventually form, easily photographed around relatively young stars. 
A) a contracting spherical cloud of gas surrounding a newly formed star, in which planets are forming. 
B) the expanding nebula formed by the supernova explosion of a massive star. 
C) an expanding gas shell surrounding a hot, white dwarf star. 
D) a disk-shaped nebula of dust and gas from which planets will eventually form, easily photographed around relatively young stars.

Question 3

A star of 25 M ? spends roughly what percentage of its life as a main-sequence star? (See Table 20-1 of Universe, 11th ed.)

Accepted Answer

A) about 10% 
B) 91% 
C) very little, less than 1% 
D) about 50% 
A) about 10% 
B) 91% 
C) very little, less than 1% 
D) about 50%

Question 4

What is meant when a nuclear reaction is described as "thermonuclear"?

Accepted Answer

A) The temperature threshold is set by convention at 10 million K. 
B) High-speed collisions bring nuclear particles with like electric charge close enough together that nuclear binding occurs. 
C) The reaction can be triggered by heat alone; motion is not needed. 
D) Thermonuclear is another word for fusion as opposed to fission reactions. 
A) The temperature threshold is set by convention at 10 million K. 
B) High-speed collisions bring nuclear particles with like electric charge close enough together that nuclear binding occurs. 
C) The reaction can be triggered by heat alone; motion is not needed. 
D) Thermonuclear is another word for fusion as opposed to fission reactions.

Question 5

The characteristics of red supergiant stars are a brightness of:

Accepted Answer

A) 10,000 Suns and a diameter of about that of Earth's orbit. 
B) Sun and size of about that of Mercury's orbit. 
C) about 1 million Suns and a diameter of the whole solar system. 
D) about 10,000 Suns and a diameter of 1/10 of that of the Sun. 
A) 10,000 Suns and a diameter of about that of Earth's orbit. 
B) Sun and size of about that of Mercury's orbit. 
C) about 1 million Suns and a diameter of the whole solar system. 
D) about 10,000 Suns and a diameter of 1/10 of that of the Sun.

Question 6

Which of the following nuclei can act as "fuel" in a core fusion reaction?

Accepted Answer

A) 28Si (silicon) 
B) 56Fe (iron) 
C) 197Au (gold) 
D) 208Pb (lead) 
A) 28Si (silicon) 
B) 56Fe (iron) 
C) 197Au (gold) 
D) 208Pb (lead)

Question 7

What is the mass limit above which the self-gravity of stars can overcome electron degeneracy pressure?

Accepted Answer

A) 0.05 M ? 
B) 1.4 M ? 
C) 14 M ? 
D) There is no limit, because nothing in nature can overcome this quantum mechanical limit. 
A) 0.05 M ? 
B) 1.4 M ? 
C) 14 M ? 
D) There is no limit, because nothing in nature can overcome this quantum mechanical limit.

Question 8

The major source of light in the expanding shell of gas in a planetary nebula is:

Accepted Answer

A) fluorescence of the atoms, caused by UV light from the hot central white dwarf star. 
B) reflection and scattering of the light of the central white dwarf star from dust and gas in the shell. 
C) thermal heating of the dust grains by radiation from the hot central star. 
D) thermonuclear reactions in this hot gas, caused by the underlying explosion. 
A) fluorescence of the atoms, caused by UV light from the hot central white dwarf star. 
B) reflection and scattering of the light of the central white dwarf star from dust and gas in the shell. 
C) thermal heating of the dust grains by radiation from the hot central star. 
D) thermonuclear reactions in this hot gas, caused by the underlying explosion.

Question 9

What causes thermal pulses in low-mass stars?

Accepted Answer

A) Thermal pulses are the end result of the 5-minute vibrations like those we observe on the Sun. 
B) The internal structure of these low-mass stars becomes unstable as they cross the instability strip on the main sequence. 
C) A helium shell flash occurs. This re-ignites the helium shell and triggers an expansion of the outer layers. 
D) Spent nuclear "ash" from the helium burning shell falls onto the hydrogen-burning core, causing it to flare up. 
A) Thermal pulses are the end result of the 5-minute vibrations like those we observe on the Sun. 
B) The internal structure of these low-mass stars becomes unstable as they cross the instability strip on the main sequence. 
C) A helium shell flash occurs. This re-ignites the helium shell and triggers an expansion of the outer layers. 
D) Spent nuclear "ash" from the helium burning shell falls onto the hydrogen-burning core, causing it to flare up.

Question 10

The progenitor of SN 1987A was a smaller blue supergiant rather than a larger red supergiant when the core erupted as a supernova. What difference did this make?

Accepted Answer

A) Blue indicates a hotter surface temperature. Thus, this was a brighter supernova than it would have been if the progenitor had been a red supergiant. 
B) Blue supergiants are inherently more massive and more compact than red supergiants. Thus, this was a brighter supernova than it would have been if the progenitor had been a red supergiant. 
C) The more compact state of the blue supernova meant that more energy was required to lift the outer layers away from the core, and thus, less energy remained to increase the luminosity. 
D) Blue supergiants are younger than red supergiants. Thus, fewer metals had been formed in the supergiant, and the resulting supernova remnant contained fewer metals than it would have had it erupted while a red supernova. 
A) Blue indicates a hotter surface temperature. Thus, this was a brighter supernova than it would have been if the progenitor had been a red supergiant. 
B) Blue supergiants are inherently more massive and more compact than red supergiants. Thus, this was a brighter supernova than it would have been if the progenitor had been a red supergiant. 
C) The more compact state of the blue supernova meant that more energy was required to lift the outer layers away from the core, and thus, less energy remained to increase the luminosity. 
D) Blue supergiants are younger than red supergiants. Thus, fewer metals had been formed in the supergiant, and the resulting supernova remnant contained fewer metals than it would have had it erupted while a red supernova.

Question 11

As a white dwarf evolves, the direction of its motion on the Hertzsprung-Russell diagram below the main sequence is upper right to lower left, which means that:

Accepted Answer

A) its size must be increasing; therefore, its luminosity is also increasing. 
B) the release of gravitational energy heats the star as it shrinks, and it will die as a hot but very small star. 
C) its size or radius remains constant as it cools and becomes less luminous. 
D) it shrinks as it cools, becoming a cold neutron star. 
A) its size must be increasing; therefore, its luminosity is also increasing. 
B) the release of gravitational energy heats the star as it shrinks, and it will die as a hot but very small star. 
C) its size or radius remains constant as it cools and becomes less luminous. 
D) it shrinks as it cools, becoming a cold neutron star.

Question 12

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB) phase, as a result of mass loss to space by its stellar wind?

Accepted Answer

A) 0.6 M ? 
B) almost 1 M ? , because mass loss is negligible for a low-mass star like the Sun 
C) 0.1 and 0.2 M ? , because the Sun will lose most of its mass 
D) 0.9 M ? 
A) 0.6 M ? 
B) almost 1 M ? , because mass loss is negligible for a low-mass star like the Sun 
C) 0.1 and 0.2 M ? , because the Sun will lose most of its mass 
D) 0.9 M ?

Question 13

A blue (hot) supergiant is 10 times larger in diameter than the Sun, but a red (cool) supergiant of the same luminosity has a diameter 1000 times that of the Sun. How does the surface temperature of the blue supergiant compare to that of the red supergiant?

Accepted Answer

A) They have the same luminosity, so they must have the same surface temperature. 
B) The surface temperature of the blue supergiant is 10 times the surface temperature of the red supergiant. 
C) The surface temperature of the blue supergiant is 100 times the surface temperature of the red supergiant. 
D) The surface temperature of the blue supergiant is 1000 times the surface temperature of the red supergiant. 
A) They have the same luminosity, so they must have the same surface temperature. 
B) The surface temperature of the blue supergiant is 10 times the surface temperature of the red supergiant. 
C) The surface temperature of the blue supergiant is 100 times the surface temperature of the red supergiant. 
D) The surface temperature of the blue supergiant is 1000 times the surface temperature of the red supergiant.

Question 14

What was the effective "neutrino energy luminosity" (energy carried away by neutrinos) of the SN 1987A supernova for a few seconds following the explosion compared to relatively well-known electromagnetic luminosities?

Accepted Answer

A) 1 million times greater than that of the observable universe 
B) 10 times greater than the total observable universe 
C) 10 times greater than the total output of the stars in our galaxy 
D) 1 million times greater than the luminosity of the Sun 
A) 1 million times greater than that of the observable universe 
B) 10 times greater than the total observable universe 
C) 10 times greater than the total output of the stars in our galaxy 
D) 1 million times greater than the luminosity of the Sun

Question 15

If SN 1987A produces 1057 neutrinos per second (uniformly in all directions), and it is at a distance of 51,500 pc (=1.59 × 1021 m), what would be the flux of neutrinos at an Earth-based detector with an area of 1 square meter?

Accepted Answer

A) 3.15 × 1013 
B) 3.96 × 1014 
C) 6.29 × 1035 
D) 3.18 × 10100 
A) 3.15 × 1013 
B) 3.96 × 1014 
C) 6.29 × 1035 
D) 3.18 × 10100

Question 16

There is a mass limit for a star in the white dwarf phase, the Chandrasekhar limit, beyond which the star can no longer support its own weight. This mass limit, in terms of solar mass, is:

Accepted Answer

A) 1.4. 
B) 14. 
C) 30. 
D) 0.2. 
A) 1.4. 
B) 14. 
C) 30. 
D) 0.2.

Question 17

The most important development in the interior of a star of moderate mass that leads to the red giant phase is:

Accepted Answer

A) a runaway nuclear furnace and eventual explosion in the star's interior, destroying the star and leaving only a rapidly expanding shell of gas. 
B) the cessation of hydrogen "burning" in the core, leading to core contraction and overall star expansion. 
C) expansion of the whole star, leading to lower temperatures throughout the star and the turnoff of the nuclear furnace in the core. 
D) contraction of the whole star, which quenches the nuclear furnace in the core and leads to cooling of the surface. 
A) a runaway nuclear furnace and eventual explosion in the star's interior, destroying the star and leaving only a rapidly expanding shell of gas. 
B) the cessation of hydrogen "burning" in the core, leading to core contraction and overall star expansion. 
C) expansion of the whole star, leading to lower temperatures throughout the star and the turnoff of the nuclear furnace in the core. 
D) contraction of the whole star, which quenches the nuclear furnace in the core and leads to cooling of the surface.

Question 18

Which of the energy-transporting processes in a star's interior also plays a role in moving heavy elements from their production region to the star's surface and from there into outer space?

Accepted Answer

A) Transport is not necessary because heavy elements are produced at the star's surface by fusion reactions in the late evolutionary phases of a star. 
B) radiative diffusion, by radiation pressure 
C) conduction 
D) convection 
A) Transport is not necessary because heavy elements are produced at the star's surface by fusion reactions in the late evolutionary phases of a star. 
B) radiative diffusion, by radiation pressure 
C) conduction 
D) convection

Question 19

If you were to increase the mass of a white dwarf star in some way:

Accepted Answer

A) its radius would become smaller. 
B) it would reject the mass, because the electrons within the star are in a degenerate state and generate a very large outward pressure. 
C) its radius would become larger. 
D) its radius would remain the same, because the electrons in the stellar material are in a degenerate state. 
A) its radius would become smaller. 
B) it would reject the mass, because the electrons within the star are in a degenerate state and generate a very large outward pressure. 
C) its radius would become larger. 
D) its radius would remain the same, because the electrons in the stellar material are in a degenerate state.

Question 20

The one material transported from the core to the surface in all three dredge-ups is:

Accepted Answer

A) hydrogen. 
B) helium. 
C) carbon. 
D) oxygen. 
A) hydrogen. 
B) helium. 
C) carbon. 
D) oxygen.

Exam 20: Stellar Evolution: The Death of Stars

Convection that reaches from the core to the surface of a star is important in each of the following EXCEPT ONE. Which is the exception?

A planetary nebula is:

A star of 25 M ? spends roughly what percentage of its life as a main-sequence star? (See Table 20-1 of Universe, 11th ed.)

What is meant when a nuclear reaction is described as "thermonuclear"?

The characteristics of red supergiant stars are a brightness of:

Which of the following nuclei can act as "fuel" in a core fusion reaction?

What is the mass limit above which the self-gravity of stars can overcome electron degeneracy pressure?

The major source of light in the expanding shell of gas in a planetary nebula is:

What causes thermal pulses in low-mass stars?

The progenitor of SN 1987A was a smaller blue supergiant rather than a larger red supergiant when the core erupted as a supernova. What difference did this make?

As a white dwarf evolves, the direction of its motion on the Hertzsprung-Russell diagram below the main sequence is upper right to lower left, which means that:

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB) phase, as a result of mass loss to space by its stellar wind?

A blue (hot) supergiant is 10 times larger in diameter than the Sun, but a red (cool) supergiant of the same luminosity has a diameter 1000 times that of the Sun. How does the surface temperature of the blue supergiant compare to that of the red supergiant?

What was the effective "neutrino energy luminosity" (energy carried away by neutrinos) of the SN 1987A supernova for a few seconds following the explosion compared to relatively well-known electromagnetic luminosities?

If SN 1987A produces 1057 neutrinos per second (uniformly in all directions), and it is at a distance of 51,500 pc (=1.59 × 1021 m), what would be the flux of neutrinos at an Earth-based detector with an area of 1 square meter?

There is a mass limit for a star in the white dwarf phase, the Chandrasekhar limit, beyond which the star can no longer support its own weight. This mass limit, in terms of solar mass, is:

The most important development in the interior of a star of moderate mass that leads to the red giant phase is:

Which of the energy-transporting processes in a star's interior also plays a role in moving heavy elements from their production region to the star's surface and from there into outer space?

If you were to increase the mass of a white dwarf star in some way:

The one material transported from the core to the surface in all three dredge-ups is:

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

If SN 1987A produces 10⁵⁷ neutrinos per second (uniformly in all directions), and it is at a distance of 51,500 pc (=1.59 × 10²¹ m), what would be the flux of neutrinos at an Earth-based detector with an area of 1 square meter?