ASTR EXAM 2 CH 17

Which of the following stars will live longest?

1 solar-mass star

In the context of understanding stellar lives, "high-mass" stars have masses______________.

more than about 8 times the mass of our Sun

Which of the following lists the stages of life for a low-mass star in the correct order?

protostar, main-sequence star, red giant, planetary nebula, white dwarf

What happens when a main-sequence star exhausts its core hydrogen fuel supply?

The core shrinks while the rest of the star expands.

The main source of energy for a star as it grows in size to become a red giant is ______.

hydrogen fusion in a shell surrounding the central core

The overall helium fusion reaction is:

Three helium nuclei fuse to form one carbon nucleus.

What is a helium flash?

The sudden onset of helium fusion in the core of a low-mass star.

An H-R diagram for a globular cluster will show a horizontal branch - a line of stars above the main-sequence but to the left of the subgiants and red giants. Which of the following statements about these horizontal branch stars is true?

They generate energy through both hydrogen fusion and helium fusion.

What is a planetary nebula?

Gas ejected from a low-mass star in the final stage of its life.

The ultimate fate of our Sun is to _____

become a white dwarf that will slowly cool with time

Which low-mass star does not have fusion occurring in its central core?

a red giant

How are low-mass red giant stars important to our existence?

These stars manufactured most of the carbon atoms in our bodies.

Which of the following pairs of atomic nuclei would feel the strongest repulsive electromagnetic force if you tried to push them together?

helium and helium

Which of the following stars will certainly end its life in a supernova?

a 10 solar mass star

What is the CNO cycle?

a set of steps by which four hydrogen nuclei fuse into one helium nucleus

In order to predict whether a star will eventually fuse oxygen into a heavier element, what do you need to know about the star?

its mass

Why is iron significant to understanding how a supernova occurs?

Iron cannot release energy either by fission or fusion.

After a supernova explosion, the remains of the stellar core ______.

may be either a neutron star or a black hole

Why is Supernova 1987A particularly important to astronomers?

It is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.

Algol consist of a 3.7 MSun main-sequence star and a 0.8 MSun subgiant. Why does this seem surprising, at least at first?

The two stars should be the same age, so we'd expect the subgiant to be more massive than the main-sequence star.

Where does gold (the element) come from?

it is produced during the supernova explosions of high-mass stars

Our Sun is considered to be a ______.

low-mass star

Which of the following types of data provide evidence that helps us understand the life tracks of low-mass stars?

H-R diagrams of globular clusters

Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main sequence star?

Fusion reactions are producing energy at a greater rate in the red giant.

Which of the following describes a star with a hydrogen-burning shell and an inert helium core?

It is a subgiant that grows in luminosity until helium fusion begins in the central core.

Which of the following observations would not be likely to provide information about the final, explosive stages of a star's life?

decades of continuous monitoring of red giants in a globular cluster

Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?

Planetary nebula formation is more common.

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) helium core?

IV

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
Which stage lasts the longest?

III

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) carbon core surrounded by shells of helium and hydrogen burning?

VIII

Carbon fusion occurs in high-mass stars but not in low-mass stars because _________.

the cores of low-mass stars never get hot enough for carbon fusion

Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high-mass star is not true?

Each successive stage lasts for approximately the same amount of time

Which event marks the beginning of a supernova?

The sudden collapse of an iron core into a compact ball of neutrons.

Suppose that the star Betelgeuse (the upper left shoulder of Orion) were to supernova tomorrow (as seen here on Earth). What would it look like to the naked eye?

Betelgeuse would remain a dot of light, but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime.

Suppose that hydrogen, rather than iron, had the lowest mass per nuclear particle. Which of the following would be true?

Nuclear fusion could not power stars.

Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, and magnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?

At the end of a high-mass star's life, it produces new elements through a series of helium capture reactions.

A spinning neutron star has been observed at the center of a ______.

supernova remnant

You discover a binary star system in which one star is a 15 MSun main-sequence star and the other is a 10 MSun giant. How do we think that a star system such as this might have come to exist?

The giant must once have been the more massive star, but is now less massive because it transferred some of its mass to its companion.

Tidal forces are very important to the Algol system today, but were not important when both stars were still on the main sequence. Why not?

Main sequence stars in a system like the Algol system are small compared to their physical separation.

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage is the star's energy supplied by primarily by gravitational contraction?

II

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
What will happen to the star after stage viii?

Its outer layers will be ejected as a planetary nebula and its core will become a white dwarf.

In this diagram, red balls represent protons and gray balls represent neutrons. What reaction is being shown?

fusion of helium into carbon

This is the HR diagram for stars in a 12-billion-year-old globular cluster. Based on our understanding of stellar lives, which of the four labeled stars is currently generating energy through hydrogen fusion in a shell around an inert (non-burning) helium core.

III

This H-R diagram shows the life track of a 1 MSun star from the time it first becomes a main-sequence star. Which numbered point represents the star when it has both hydrogen-burning and helium-burning shells around an inert carbon core?

4

This Hubble Space Telescope photo shows a planetary nebula. What is the white dot in the center (indicated by the arrow)?

a white dwarf

Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Based on your understanding of stellar lives, the mass of this star is probably:

about 10 (or more) solar masses

Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Which of the following statements about this star is most likely to be true?

The star will explode as a supernova within a few days.

According to this diagram, how much more abundant is hydrogen in the universe than nitrogen?

hydrogen is about 10,000 times as abundant as nitrogen

This photo shows the famous Crab Nebula. What is it?

An expanding cloud of remains from a star that died in a supernova.

The arrow in the photo on the left shows the star that we see as a supernova in the photo on the right. What can we conclude about this star?

It was a high-mass star with at least 8 times the mass of the Sun.

Suppose you had looked with your naked eye at the supernova on the night it was photographed in the "after" photo. Assuming that it was bright enough to see (it was), what would it have looked like to your naked eye?

Like a single star in the night sky.

ASTR EXAM 2 CH 17 - Subjecto.com

ASTR EXAM 2 CH 17

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Which of the following stars will live longest?

1 solar-mass star

In the context of understanding stellar lives, "high-mass" stars have masses______________.

more than about 8 times the mass of our Sun

Which of the following lists the stages of life for a low-mass star in the correct order?

protostar, main-sequence star, red giant, planetary nebula, white dwarf

What happens when a main-sequence star exhausts its core hydrogen fuel supply?

The core shrinks while the rest of the star expands.

The main source of energy for a star as it grows in size to become a red giant is ______.

hydrogen fusion in a shell surrounding the central core

The overall helium fusion reaction is:

Three helium nuclei fuse to form one carbon nucleus.

What is a helium flash?

The sudden onset of helium fusion in the core of a low-mass star.

An H-R diagram for a globular cluster will show a horizontal branch – a line of stars above the main-sequence but to the left of the subgiants and red giants. Which of the following statements about these horizontal branch stars is true?

They generate energy through both hydrogen fusion and helium fusion.

What is a planetary nebula?

Gas ejected from a low-mass star in the final stage of its life.

The ultimate fate of our Sun is to _____

become a white dwarf that will slowly cool with time

Which low-mass star does not have fusion occurring in its central core?

a red giant

How are low-mass red giant stars important to our existence?

These stars manufactured most of the carbon atoms in our bodies.

Which of the following pairs of atomic nuclei would feel the strongest repulsive electromagnetic force if you tried to push them together?

helium and helium

Which of the following stars will certainly end its life in a supernova?

a 10 solar mass star

What is the CNO cycle?

a set of steps by which four hydrogen nuclei fuse into one helium nucleus

In order to predict whether a star will eventually fuse oxygen into a heavier element, what do you need to know about the star?

its mass

Why is iron significant to understanding how a supernova occurs?

Iron cannot release energy either by fission or fusion.

After a supernova explosion, the remains of the stellar core ______.

may be either a neutron star or a black hole

Why is Supernova 1987A particularly important to astronomers?

It is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.

Algol consist of a 3.7 MSun main-sequence star and a 0.8 MSun subgiant. Why does this seem surprising, at least at first?

The two stars should be the same age, so we’d expect the subgiant to be more massive than the main-sequence star.

Where does gold (the element) come from?

it is produced during the supernova explosions of high-mass stars

Our Sun is considered to be a ______.

low-mass star

Which of the following types of data provide evidence that helps us understand the life tracks of low-mass stars?

H-R diagrams of globular clusters

Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main sequence star?

Fusion reactions are producing energy at a greater rate in the red giant.

Which of the following describes a star with a hydrogen-burning shell and an inert helium core?

It is a subgiant that grows in luminosity until helium fusion begins in the central core.

Which of the following observations would not be likely to provide information about the final, explosive stages of a star’s life?

decades of continuous monitoring of red giants in a globular cluster

Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?

Planetary nebula formation is more common.

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) helium core?

IV

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
Which stage lasts the longest?

III

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) carbon core surrounded by shells of helium and hydrogen burning?

VIII

Carbon fusion occurs in high-mass stars but not in low-mass stars because _________.

the cores of low-mass stars never get hot enough for carbon fusion

Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high-mass star is not true?

Each successive stage lasts for approximately the same amount of time

Which event marks the beginning of a supernova?

The sudden collapse of an iron core into a compact ball of neutrons.

Suppose that the star Betelgeuse (the upper left shoulder of Orion) were to supernova tomorrow (as seen here on Earth). What would it look like to the naked eye?

Betelgeuse would remain a dot of light, but would suddenly become so bright that, for a few weeks, we’d be able to see this dot in the daytime.

Suppose that hydrogen, rather than iron, had the lowest mass per nuclear particle. Which of the following would be true?

Nuclear fusion could not power stars.

Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, and magnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?

At the end of a high-mass star’s life, it produces new elements through a series of helium capture reactions.

A spinning neutron star has been observed at the center of a ______.

supernova remnant

You discover a binary star system in which one star is a 15 MSun main-sequence star and the other is a 10 MSun giant. How do we think that a star system such as this might have come to exist?

The giant must once have been the more massive star, but is now less massive because it transferred some of its mass to its companion.

Tidal forces are very important to the Algol system today, but were not important when both stars were still on the main sequence. Why not?

Main sequence stars in a system like the Algol system are small compared to their physical separation.

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage is the star’s energy supplied by primarily by gravitational contraction?

II

This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
What will happen to the star after stage viii?

Its outer layers will be ejected as a planetary nebula and its core will become a white dwarf.

In this diagram, red balls represent protons and gray balls represent neutrons. What reaction is being shown?

fusion of helium into carbon

This is the HR diagram for stars in a 12-billion-year-old globular cluster. Based on our understanding of stellar lives, which of the four labeled stars is currently generating energy through hydrogen fusion in a shell around an inert (non-burning) helium core.

III

This H-R diagram shows the life track of a 1 MSun star from the time it first becomes a main-sequence star. Which numbered point represents the star when it has both hydrogen-burning and helium-burning shells around an inert carbon core?

4

This Hubble Space Telescope photo shows a planetary nebula. What is the white dot in the center (indicated by the arrow)?

a white dwarf

Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Based on your understanding of stellar lives, the mass of this star is probably:

about 10 (or more) solar masses

Suppose a particular star has a core that is undergoing several stages of fusion simultaneously, as shown in this diagram. Which of the following statements about this star is most likely to be true?

The star will explode as a supernova within a few days.

According to this diagram, how much more abundant is hydrogen in the universe than nitrogen?

hydrogen is about 10,000 times as abundant as nitrogen

This photo shows the famous Crab Nebula. What is it?

An expanding cloud of remains from a star that died in a supernova.

The arrow in the photo on the left shows the star that we see as a supernova in the photo on the right. What can we conclude about this star?

It was a high-mass star with at least 8 times the mass of the Sun.

Suppose you had looked with your naked eye at the supernova on the night it was photographed in the "after" photo. Assuming that it was bright enough to see (it was), what would it have looked like to your naked eye?

Like a single star in the night sky.

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