Question 1

What is the escape velocity from the surface of a 1 M $\odot$  AGB star that has a radius of 100 R $\odot$ ?

Accepted Answer

A)  60 km/s 
B)  120 km/s 
C)  240 km/s 
D)  620 km/s 
E)  800 km/s 
A)  60 km/s 
B)  120 km/s 
C)  240 km/s 
D)  620 km/s 
E)  800 km/s

Question 2

When the Sun becomes an AGB star, its radius will be approximately 100 R $\odot$ . If its mass at this point will be approximately the same as it is now, how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that g =GM/R2.

Accepted Answer

Surface gravity: g = GM/R². g

Question 3

The percentage of hydrogen in the Sun's core today is roughly half of what it was originally.

Accepted Answer

A) True 
 B)False

Question 4

When a spectral-type G2 star like the Sun leaves the main sequence:

Accepted Answer

A)  its luminosity and surface temperature both stay the same 
B)  its luminosity and surface temperature both decrease 
C)  its luminosity increases and its surface temperature decreases 
D)  its luminosity and surface temperature both increase 
E)  its luminosity decreases and its surface temperature increases 
A)  its luminosity and surface temperature both stay the same 
B)  its luminosity and surface temperature both decrease 
C)  its luminosity increases and its surface temperature decreases 
D)  its luminosity and surface temperature both increase 
E)  its luminosity decreases and its surface temperature increases

Question 5

What types of chemical elements can low-mass stars contribute to the enrichment of the interstellar medium and how are they produced?

Accepted Answer

Low-mass stars can enrich the interstell

Question 6

A Type I supernova can be as luminous as 10 billion L $\odot$ .

Accepted Answer

A) True 
 B)False

Question 7

A low-mass star that burns helium in its core and hydrogen in a shell surrounding the core is more luminous than a similar star that burns only hydrogen in a shell around a dead core.

Accepted Answer

A) True 
 B)False

Question 8

What would you need to measure about a planetary nebula to determine how long ago its parent star died?

Accepted Answer

A)  the mass of the white dwarf 
B)  the mass and radius of the white dwarf 
C)  the nebula's temperature and radius 
D)  the nebula's radius and expansion velocity 
E)  the composition of the gas in the nebula 
A)  the mass of the white dwarf 
B)  the mass and radius of the white dwarf 
C)  the nebula's temperature and radius 
D)  the nebula's radius and expansion velocity 
E)  the composition of the gas in the nebula

Question 9

A white dwarf with a temperature of 30,000 K would shine brightest at what wavelength?

Accepted Answer

A)  4 nm, X-rays 
B)  100 nm, ultraviolet 
C)  400 nm, blue visible 
D)  1 $\mu$m, infrared 
E)  10 $\mu$m, infrared 
A)  4 nm, X-rays 
B)  100 nm, ultraviolet 
C)  400 nm, blue visible 
D)  1 $\mu$m, infrared 
E)  10 $\mu$m, infrared

Question 10

A main-sequence star is unique because:

Accepted Answer

A)  hydrostatic equilibrium exists at all radii 
B)  energy transport occurs via convection throughout much of its interior 
C)  carbon burning occurs in its core 
D)  it emits strong surface winds 
E)  hydrogen burning occurs in its core 
A)  hydrostatic equilibrium exists at all radii 
B)  energy transport occurs via convection throughout much of its interior 
C)  carbon burning occurs in its core 
D)  it emits strong surface winds 
E)  hydrogen burning occurs in its core

Question 11

The main-sequence lifetime of a star is given by the equation:

Accepted Answer

A)  " $ \tau $ $\infty$ M/L" 
B)  " $ \tau $ $\infty$ L/M" 
C)  " $ \tau $ $\infty$ M 2/L" 
D)  " $ \tau $ $\infty$L2/L" 
E)  " $ \tau $ $\infty$ M/L2" 
A)  " $ \tau $ $\infty$ M/L" 
B)  " $ \tau $ $\infty$ L/M" 
C)  " $ \tau $ $\infty$ M 2/L" 
D)  " $ \tau $ $\infty$L2/L" 
E)  " $ \tau $ $\infty$ M/L2"

Question 12

Explain what the triple-alpha process is and when it takes place in evolving stars.

Accepted Answer

The triple-alpha process is the way that

Question 13

A Type I supernova occurs when a white dwarf exceeds a mass of:

Accepted Answer

A)  0.8 M $\odot$ 
B)  1.4 M $\odot$ 
C)  2.3 M $\odot$ 
D)  5.4 M $\odot$ 
E)  10 M $\odot$ 
A)  0.8 M $\odot$ 
B)  1.4 M $\odot$ 
C)  2.3 M $\odot$ 
D)  5.4 M $\odot$ 
E)  10 M $\odot$

Question 14

Which of the stellar spectral types shown below would be the least likely to have planets with life?

Accepted Answer

A)  B0 
B)  G2 
C)  K0 
D)  M0 
E)  M5 
A)  B0 
B)  G2 
C)  K0 
D)  M0 
E)  M5

Question 15

In what two ways does temperature affect the rate of nuclear reactions?

Accepted Answer

Higher temperature means atomic nuclei a

Question 16

Consider a 1 M$\odot$ star's journey up the red giant branch. Its luminosity will change from 10 L$\odot$ to nearly 1,000 L$\odot$. How will its temperature and radius change as the star ascends? (Recall that L $\infty$R2T 4.)

Accepted Answer

The red giant star's temperature will es

Question 17

In a white dwarf, what is the source of pressure that halts its contraction as it cools?

Accepted Answer

A)  thermal pressure of the extremely hot gas 
B)  electrons packed so closely that they become incompressible 
C)  neutrons that resist being pressed further together 
D)  carbon nuclei that repel each other strongly because they each contain six protons 
E)  rapid rotation 
A)  thermal pressure of the extremely hot gas 
B)  electrons packed so closely that they become incompressible 
C)  neutrons that resist being pressed further together 
D)  carbon nuclei that repel each other strongly because they each contain six protons 
E)  rapid rotation

Question 18

What stops a red giant from cooling to continuously lower temperatures, and why?

Accepted Answer

The H ^- ion: It acts as a th

Question 19

As a subgiant star becomes a red giant, its luminosity increases while its temperature remains approximately constant. What does this mean?

Accepted Answer

A)  The radius is decreasing. 
B)  The radius is increasing. 
C)  The star is getting hotter. 
D)  The star is losing mass. 
E)  The star is rotating more slowly. 
A)  The radius is decreasing. 
B)  The radius is increasing. 
C)  The star is getting hotter. 
D)  The star is losing mass. 
E)  The star is rotating more slowly.

Question 20

Why are novae thought to reoccur repeatedly?

Accepted Answer

The explosive hydrogen burning on the su

Exam 16: Evolution of Low-Mass Stars

What is the escape velocity from the surface of a 1 M ⊙\odot⊙ AGB star that has a radius of 100 R ⊙\odot⊙ ?

When the Sun becomes an AGB star, its radius will be approximately 100 R ⊙\odot⊙ . If its mass at this point will be approximately the same as it is now, how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that g =GM/R2.

The percentage of hydrogen in the Sun's core today is roughly half of what it was originally.

When a spectral-type G2 star like the Sun leaves the main sequence:

What types of chemical elements can low-mass stars contribute to the enrichment of the interstellar medium and how are they produced?

A Type I supernova can be as luminous as 10 billion L ⊙\odot⊙ .

A low-mass star that burns helium in its core and hydrogen in a shell surrounding the core is more luminous than a similar star that burns only hydrogen in a shell around a dead core.

What would you need to measure about a planetary nebula to determine how long ago its parent star died?

A white dwarf with a temperature of 30,000 K would shine brightest at what wavelength?

A main-sequence star is unique because:

The main-sequence lifetime of a star is given by the equation:

Explain what the triple-alpha process is and when it takes place in evolving stars.

A Type I supernova occurs when a white dwarf exceeds a mass of:

Which of the stellar spectral types shown below would be the least likely to have planets with life?

In what two ways does temperature affect the rate of nuclear reactions?

Consider a 1 M ⊙\odot⊙ star's journey up the red giant branch. Its luminosity will change from 10 L ⊙\odot⊙ to nearly 1,000 L ⊙\odot⊙ . How will its temperature and radius change as the star ascends? (Recall that L ∞\infty∞ R2T 4.)

In a white dwarf, what is the source of pressure that halts its contraction as it cools?

What stops a red giant from cooling to continuously lower temperatures, and why?

As a subgiant star becomes a red giant, its luminosity increases while its temperature remains approximately constant. What does this mean?

Why are novae thought to reoccur repeatedly?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornmentsmoons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of High-Mass Stars

Relativity and Black Holes

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

What is the escape velocity from the surface of a 1 M _$\odot$ AGB star that has a radius of 100 R _$\odot$ ?

When the Sun becomes an AGB star, its radius will be approximately 100 R _$\odot$ . If its mass at this point will be approximately the same as it is now, how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that g =GM/R².

A Type I supernova can be as luminous as 10 billion L _$\odot$ .

Consider a 1 M_$\odot$ star's journey up the red giant branch. Its luminosity will change from 10 L_$\odot$ to nearly 1,000 L_$\odot$. How will its temperature and radius change as the star ascends? (Recall that L $\infty$ R²T ⁴.)