Question 1

Degenerate refers to a state of matter at:

Accepted Answer

A) low density 
B) high density 
C) low luminosity 
D) high luminosity 
E) high temperature 
A) low density 
B) high density 
C) low luminosity 
D) high luminosity 
E) high temperature

Question 2

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 3

What is the name of the nuclear reaction illustrated here?

Accepted Answer

A) the proton-proton chain 
B) the CNO cycle 
C) beta decay 
D) the triple-alpha process 
E) the alpha-beta reaction 
A) the proton-proton chain 
B) the CNO cycle 
C) beta decay 
D) the triple-alpha process 
E) the alpha-beta reaction

Question 4

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 5

When helium fusion begins in the core of a red giant star,the situation quickly gets out of control because electron-degeneracy pressure does not respond to changes in:

Accepted Answer

A) luminosity 
B) density 
C) gravity 
D) temperature 
E) magnetic field strength 
A) luminosity 
B) density 
C) gravity 
D) temperature 
E) magnetic field strength

Question 6

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

Accepted Answer

Higher temperature means atomic nuclei a

Question 7

Why are novae thought to reoccur repeatedly?

Accepted Answer

The explosive hydrogen burning on the su

Question 8

The Sun eventually could become a nova.

Accepted Answer

A) True 
 B)False

Question 9

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 10

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 11

A 1M⨀ star in a binary system could create the following chemical element and eject it into the interstellar medium:

Accepted Answer

A) carbon 
B) helium 
C) iron 
D) gold 
E) all of the above 
A) carbon 
B) helium 
C) iron 
D) gold 
E) all of the above

Question 12

A white dwarf star has a luminosity equal to 10−4 L⨀ 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 ∝ R²T⁴.(L/

Question 13

A low-mass main-sequence star's climb up the red giant branch is halted by:

Accepted Answer

A) the end of hydrogen shell burning 
B) the beginning of helium fusion in the core 
C) electron-degeneracy pressure in the core 
D) instabilities in the star's expanding outer layers 
E) an explosion that destroys the star 
A) the end of hydrogen shell burning 
B) the beginning of helium fusion in the core 
C) electron-degeneracy pressure in the core 
D) instabilities in the star's expanding outer layers 
E) an explosion that destroys the star

Question 14

Why does the core of a main-sequence star have to be hotter to burn helium into carbon than hydrogen into helium?

Accepted Answer

A helium nucleus has two protons and a n

Question 15

During which phase of the evolution of a low-mass star does it have two separate regions of nuclear burning occurring in its interior?

Accepted Answer

A) pre-main sequence 
B) main sequence 
C) red giant 
D) horizontal branch 
E) white dwarf 
A) pre-main sequence 
B) main sequence 
C) red giant 
D) horizontal branch 
E) white dwarf

Question 16

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

Question 17

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 18

As a main-sequence star burns its core supply of hydrogen,what happens?

Accepted Answer

A) Helium begins to fuse throughout the core. 
B) Helium fuses in a shell surrounding the core. 
C) Helium fusion takes place only at the very center of the core,where temperature and pressure are highest. 
D) Helium builds up as ash in the core. 
E) Helium builds up everywhere in the star's interior. 
A) Helium begins to fuse throughout the core. 
B) Helium fuses in a shell surrounding the core. 
C) Helium fusion takes place only at the very center of the core,where temperature and pressure are highest. 
D) Helium builds up as ash in the core. 
E) Helium builds up everywhere in the star's interior.

Question 19

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 20

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

Exam 16: Evolution of Low-Mass Stars

Degenerate refers to a state of matter at:

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?

What is the name of the nuclear reaction illustrated here?

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?

When helium fusion begins in the core of a red giant star,the situation quickly gets out of control because electron-degeneracy pressure does not respond to changes in:

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

Why are novae thought to reoccur repeatedly?

The Sun eventually could become a nova.

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

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

A 1M⨀ star in a binary system could create the following chemical element and eject it into the interstellar medium:

A white dwarf star has a luminosity equal to 10−4 L⨀ 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?

A low-mass main-sequence star's climb up the red giant branch is halted by:

Why does the core of a main-sequence star have to be hotter to burn helium into carbon than hydrogen into helium?

During which phase of the evolution of a low-mass star does it have two separate regions of nuclear burning occurring in its interior?

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

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?

As a main-sequence star burns its core supply of hydrogen,what happens?

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

The gas in a planetary nebula is composed of:

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 Adornments Moons 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

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 1M_⨀ star in a binary system could create the following chemical element and eject it into the interstellar medium:

A white dwarf star has a luminosity equal to 10⁻⁴ L_⨀ 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?