Question 1

The more massive a star is, the more hydrogen it has to burn, and the longer its main-sequence lifetime lasts.

Accepted Answer

A) True 
 B)False

Question 2

If a main-sequence star were gaining mass by being in an interacting binary system, what would happen to that star's luminosity and why?

Accepted Answer

A)  The luminosity would increase because the star would become a nova. 
B)  The luminosity would increase because the star's central pressure would rise and the rate of nuclear reactions would increase. 
C)  The luminosity would decrease because the outgoing energy has to pass through more layers in the star. 
D)  The luminosity would decrease because high-mass stars are fainter. 
E)  The luminosity would decrease because the star would quickly turn into a white dwarf. 
A)  The luminosity would increase because the star would become a nova. 
B)  The luminosity would increase because the star's central pressure would rise and the rate of nuclear reactions would increase. 
C)  The luminosity would decrease because the outgoing energy has to pass through more layers in the star. 
D)  The luminosity would decrease because high-mass stars are fainter. 
E)  The luminosity would decrease because the star would quickly turn into a white dwarf.

Question 3

How can the core of a star be degenerate with respect to the electrons but nondegenerate with respect to the nuclei?

Accepted Answer

(1) Quantum mechanics says electrons tak

Question 4

Explain the two different forms of pressure that support the core of a low-mass main-sequence star and the core of a low-mass red giant star.

Accepted Answer

The core of a low-mass main-sequence sta

Question 5

If there were mixing processes in a main-sequence star with a radiative zone (there aren't) that churned up all the material in the interior, we would expect that the main-sequence lifetime would be _________ because _________.

Accepted Answer

A)  shorter, because the star would turn into a giant faster 
B)  shorter, because the star would burn hydrogen faster and have a higher luminosity 
C)  longer, because helium nuclei have a higher mass than hydrogen nuclei 
D)  shorter, because the star would never turn into a red giant 
E)  longer, because more hydrogen would be available to burn 
A)  shorter, because the star would turn into a giant faster 
B)  shorter, because the star would burn hydrogen faster and have a higher luminosity 
C)  longer, because helium nuclei have a higher mass than hydrogen nuclei 
D)  shorter, because the star would never turn into a red giant 
E)  longer, because more hydrogen would be available to burn

Question 6

The Ring Nebula is a planetary nebula that currently has a radius of 1.2 * 1013 km and an expansion velocity of 250 km/s. Approximately how long ago did its parent star die and eject its outer layers?

Accepted Answer

A)  1,500 years ago 
B)  3,200 years ago 
C)  5,400 years ago 
D)  8,000 years ago 
E)  28,000 years ago 
A)  1,500 years ago 
B)  3,200 years ago 
C)  5,400 years ago 
D)  8,000 years ago 
E)  28,000 years ago

Question 7

Once the core of a low-mass main-sequence star runs out of hydrogen, fusion in the star stops until the core temperature is high enough for helium fusion to begin.

Accepted Answer

A) True 
 B)False

Question 8

A white dwarf star has a luminosity equal to 10- 4 L $\odot$  and a temperature twice that of the Sun (i.e., T =10,600 K). What is the radius of the white dwarf, expressed as a ratio to the solar radius?

Accepted Answer

L @#LAT-DLM& R²T ⁴

Question 9

Using the data in the table below, identify the spectral type of a star that has a main-sequence lifetime of about 10 billion years.

Accepted Answer

A)  A5 
B)  F5 
C)  K0 
D)  G2 
E)  M8 
A)  A5 
B)  F5 
C)  K0 
D)  G2 
E)  M8

Question 10

Consider a red giant star with a luminosity of 200 L $\odot$  and a radius of 50 R $\odot$ . Using the luminosity-temperature-radius relationship (L $\infty$R2T 4), calculate how hot this star's surface temperature will be compared to the Sun, whose temperature is 5,800 K.

Accepted Answer

L @#LAT-DLM& R²T ⁴

Question 11

A 10M $\odot$  star will evolve through the same phases as a 1M $\odot$  star.

Accepted Answer

A) True 
 B)False

Question 12

A low-mass red giant star's energy comes from:

Accepted Answer

A)  hydrogen burning to helium in its core 
B)  helium burning to carbon in its core 
C)  hydrogen burning to helium in a shell surrounding its core 
D)  helium burning to carbon in a shell surrounding its core 
E)  hydrogen burning to carbon in a shell surrounding its core 
A)  hydrogen burning to helium in its core 
B)  helium burning to carbon in its core 
C)  hydrogen burning to helium in a shell surrounding its core 
D)  helium burning to carbon in a shell surrounding its core 
E)  hydrogen burning to carbon in a shell surrounding its core

Question 13

The gas in a planetary nebula is composed of:

Accepted Answer

A)  primarily hydrogen from the surrounding interstellar medium 
B)  primarily hydrogen from the post-asymptotic giant branch star 
C)  hydrogen and heavier elements like helium and carbon processed in the core of the post-asymptotic giant branch star 
D)  primarily helium from the post-asymptotic giant branch star 
E)  carbon and helium from the nuclear reactions that took place on the horizontal branch 
A)  primarily hydrogen from the surrounding interstellar medium 
B)  primarily hydrogen from the post-asymptotic giant branch star 
C)  hydrogen and heavier elements like helium and carbon processed in the core of the post-asymptotic giant branch star 
D)  primarily helium from the post-asymptotic giant branch star 
E)  carbon and helium from the nuclear reactions that took place on the horizontal branch

Question 14

The luminosity of a star depends on:

Accepted Answer

A)  its mass and age 
B)  its mass 
C)  its age 
D)  its distance 
E)  its mass, age, and distance 
A)  its mass and age 
B)  its mass 
C)  its age 
D)  its distance 
E)  its mass, age, and distance

Question 15

Describe the structure of a red giant star just before the helium flash takes place. How does this compare to the structure of a horizontal-branch star?

Accepted Answer

A red giant has a nonburning helium core

Question 16

If the Milky Way formed stars at approximately a constant rate over the last 14 billion years, what fraction of the M-type stars that ever formed in it can still be found as main-sequence stars today? Note that M-type stars have a mass of approximately 0.5 M $\odot$ .

Accepted Answer

A)  10 percent 
B)  33 percent 
C)  50 percent 
D)  75 percent 
E)  100 percent 
A)  10 percent 
B)  33 percent 
C)  50 percent 
D)  75 percent 
E)  100 percent

Question 17

Calculate the main-sequence lifetimes of the following stars of different spectral types: B0 (18 M $\odot$ ), B5 (6 M $\odot$ ), A5 (2 M $\odot$ ), F5 (1.3 M $\odot$ ), and M0 (0.5 M $\odot$ ). What trend do you notice in your results?

Accepted Answer

Main-sequence lifetime: @#LAT-DLM&_MS =

Question 18

A star's surface temperature during the horizontal branch phase is determined primarily by its:

Accepted Answer

A)  luminosity 
B)  mass and chemical composition 
C)  magnetic field strength 
D)  rotation rate 
E)  radius 
A)  luminosity 
B)  mass and chemical composition 
C)  magnetic field strength 
D)  rotation rate 
E)  radius

Question 19

If a main-sequence star's core temperature increased, fusion reaction rates would decrease because the protons would be moving faster.

Accepted Answer

A) True 
 B)False

Question 20

Binary stars can evolve to become novae and supernovae because small differences in the stars' masses can mean large differences in their main-sequence lifetimes.

Accepted Answer

A) True 
 B)False

Exam 16: Evolution of Low-Mass Stars

The more massive a star is, the more hydrogen it has to burn, and the longer its main-sequence lifetime lasts.

If a main-sequence star were gaining mass by being in an interacting binary system, what would happen to that star's luminosity and why?

How can the core of a star be degenerate with respect to the electrons but nondegenerate with respect to the nuclei?

Explain the two different forms of pressure that support the core of a low-mass main-sequence star and the core of a low-mass red giant star.

If there were mixing processes in a main-sequence star with a radiative zone (there aren't) that churned up all the material in the interior, we would expect that the main-sequence lifetime would be _________ because _________.

The Ring Nebula is a planetary nebula that currently has a radius of 1.2 * 1013 km and an expansion velocity of 250 km/s. Approximately how long ago did its parent star die and eject its outer layers?

Once the core of a low-mass main-sequence star runs out of hydrogen, fusion in the star stops until the core temperature is high enough for helium fusion to begin.

A white dwarf star has a luminosity equal to 10- 4 L ⊙\odot⊙ and a temperature twice that of the Sun (i.e., T =10,600 K). What is the radius of the white dwarf, expressed as a ratio to the solar radius?

Using the data in the table below, identify the spectral type of a star that has a main-sequence lifetime of about 10 billion years.

Consider a red giant star with a luminosity of 200 L ⊙\odot⊙ and a radius of 50 R ⊙\odot⊙ . Using the luminosity-temperature-radius relationship (L ∞\infty∞ R2T 4), calculate how hot this star's surface temperature will be compared to the Sun, whose temperature is 5,800 K.

A 10M ⊙\odot⊙ star will evolve through the same phases as a 1M ⊙\odot⊙ star.

A low-mass red giant star's energy comes from:

The gas in a planetary nebula is composed of:

The luminosity of a star depends on:

Describe the structure of a red giant star just before the helium flash takes place. How does this compare to the structure of a horizontal-branch star?

If the Milky Way formed stars at approximately a constant rate over the last 14 billion years, what fraction of the M-type stars that ever formed in it can still be found as main-sequence stars today? Note that M-type stars have a mass of approximately 0.5 M ⊙\odot⊙ .

Calculate the main-sequence lifetimes of the following stars of different spectral types: B0 (18 M ⊙\odot⊙ ), B5 (6 M ⊙\odot⊙ ), A5 (2 M ⊙\odot⊙ ), F5 (1.3 M ⊙\odot⊙ ), and M0 (0.5 M ⊙\odot⊙ ). What trend do you notice in your results?

A star's surface temperature during the horizontal branch phase is determined primarily by its:

If a main-sequence star's core temperature increased, fusion reaction rates would decrease because the protons would be moving faster.

Binary stars can evolve to become novae and supernovae because small differences in the stars' masses can mean large differences in their main-sequence lifetimes.

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

If there were mixing processes in a main-sequence star with a radiative zone (there aren't) that churned up all the material in the interior, we would expect that the main-sequence lifetime would be _ because _.

The Ring Nebula is a planetary nebula that currently has a radius of 1.2 * 10¹³ km and an expansion velocity of 250 km/s. Approximately how long ago did its parent star die and eject its outer layers?

A white dwarf star has a luminosity equal to 10^- ⁴ L _$\odot$ and a temperature twice that of the Sun (i.e., T =10,600 K). What is the radius of the white dwarf, expressed as a ratio to the solar radius?

Consider a red giant star with a luminosity of 200 L _$\odot$ and a radius of 50 R _$\odot$ . Using the luminosity-temperature-radius relationship (L $\infty$ R²T ⁴), calculate how hot this star's surface temperature will be compared to the Sun, whose temperature is 5,800 K.

A 10M _$\odot$ star will evolve through the same phases as a 1M _$\odot$ star.

If the Milky Way formed stars at approximately a constant rate over the last 14 billion years, what fraction of the M-type stars that ever formed in it can still be found as main-sequence stars today? Note that M-type stars have a mass of approximately 0.5 M _$\odot$ .

Calculate the main-sequence lifetimes of the following stars of different spectral types: B0 (18 M _$\odot$ ), B5 (6 M _$\odot$ ), A5 (2 M _$\odot$ ), F5 (1.3 M _$\odot$ ), and M0 (0.5 M _$\odot$ ). What trend do you notice in your results?