Chapter 17 Homework 14 Star stuff

Question 1

The following figures show various stages during the life of a star with the same mass as the Sun. Rank the stages based on when they occur, from first to last.

Contracting cloud of gas and dust
protostar
main sequence g star
red giant
planetary nebula 
white dwarf

Answer 1

Contracting cloud of gas and dust
protostar
main sequence g star
red giant
planetary nebula 
white dwarf

Question 2

How do the properties of long-lived stars compare to those of short-lived stars?
Check all that apply.

Long-lived stars begin their lives with more mass and a larger amount of hydrogen fuel.
Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel.
Long-lived stars are more luminous during their main-sequence lives.
Long-lived stars are less luminous during their main-sequence lives.

Answer 2

Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel.
Long-lived stars are less luminous during their main-sequence lives.

Question 3

A main-sequence star twice as massive as the Sun would last __________.

about half as long as the Sun
much less than half as long as the Sun
about twice as long as the Sun
much longer than twice as long as the Sun

Answer 3

much less than half as long as the Sun

Question 4

If stars A and B are both main-sequence stars and star A has a greater fusion rate than star B, which of the following statements hold(s)?
Check all that apply.

Star A must be more luminous than star B.
Star A must be less luminous than star B.
Star A must be more massive than star B.
Star A must be less massive than star B.

Answer 4

Star A must be more luminous than star B.

Star A must be more massive than star B.

Question 5

Provided following are various stages during the life of a high-mass star. Rank the stages based on when they occur, from first to last.

contracting cloud of gas and dust
protostar
main sequence o star
red supergiant
supernova
neutron star

Answer 5

contracting cloud of gas and dust
protostar
main sequence o star
red supergiant
supernova
neutron star

Question 6

Provided following are various elements that can be produced during fusion in the core of a high mass main sequence star. Rank these elements based on when they are produced, from first to last.

helium
carbon
oxygen
iron

Answer 6

helium
carbon
oxygen
iron

Question 7

Listed following are characteristics that describe either high-mass or low-mass stars. Match these characteristics to the appropriate category. High Mass Stars

have higher fusion rate during main sequence life.
late in life fuse carbon into heavier elements.
end life as a supernova.
have longer lifetimes.
the sun is an example.
end life as a planetary nebula.
final corpse is a white dwarf.

Answer 7

have higher fusion rate during main sequence life.
late in life fuse carbon into heavier elements.
end life as a supernova.

Question 8

Listed following are characteristics that describe either high-mass or low-mass stars. Match these characteristics to the appropriate category. Low Mass Stars

have higher fusion rate during main sequence life.
late in life fuse carbon into heavier elements.
end life as a supernova.
have longer lifetimes.
the sun is an example.
end life as a planetary nebula.
final corpse is a white dwarf.

Answer 8

have longer lifetimes.
the sun is an example.
end life as a planetary nebula.
final corpse is a white dwarf.

Question 9

The Crab Nebula is the result of a ______ that was witnessed on Earth in the year 1054.

Answer 9

Supernova

Question 10

Betelgeuse is a supergiant star that will eventually supernova, which means that by mass it is classified as a _______

Answer 10

High mass star

Question 11

The debris from the death of a high-mass star forms a __________ several light years across.

Answer 11

supernova remnant

Question 12

A ______ has a density higher than the density of a white dwarf.

Answer 12

Neutron Star

Question 13

_________ actually occurred about 150,000 years ago in the Large Magellanic Cloud.

Answer 13

Supernova 1987A

Question 14

The ______ is the process by which hydrogen fusion proceeds in high-mass stars.

Answer 14

CNO cycle

Question 15

Carbon can be converted into oxygen in the cores of high-mass stars if carbon nuclei undergo a _______________.

Answer 15

Helium-capture reaction

Question 16

Which of the following stars will live longest?

4 solar mass star.
3 solar-mass star
1 solar-mass star
2 solar-mass star

Answer 16

1 solar-mass star

Question 17

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

more than about 3 times the mass of our Sun
greater than all stars, since all stars are far more massive than planets
more than about 8 times the mass of our Sun
the same as our Sun

Answer 17

more than about 8 times the mass of our Sun

Question 18

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

Answer 18

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

Question 19

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

The core immediately begins to fuse its helium into carbon.
The star becomes a neutron star.
The core shrinks while the rest of the star expands.
The entire star shrinks in size.

Answer 19

The core shrinks while the rest of the star expands.

Question 20

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

helium fusion in the central core
hydrogen fusion in a shell surrounding the central core
gravitational contraction
hydrogen fusion in the central core

Answer 20

hydrogen fusion in a shell surrounding the central core

Question 21

The overall helium fusion reaction is:

Three helium nuclei fuse to form one carbon nucleus.
Two helium nuclei fuse to form one beryllium nucleus.
Two hydrogen nuclei fuse to form one helium nucleus.
Four helium nuclei fuse to form one oxygen nucleus.

Answer 21

Three helium nuclei fuse to form one carbon nucleus.

Question 22

What is a helium flash?

The ignition of helium shell burning in a high-mass star with a carbon core.
It is another name for the helium fusion reaction.
The sudden onset of helium fusion in the core of a low-mass star.
A sudden brightening of a low-mass star, detectable from Earth by observing spectral lines of helium.

Answer 22

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

Question 23

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 have inert (non-burning) carbon cores.
They generate energy through both hydrogen fusion and helium fusion.
Their sole source of energy is hydrogen shell burning.
In a particular star cluster, all horizontal branch stars have the same spectral type.

Answer 23

They generate energy through both hydrogen fusion and helium fusion.

Question 24

What is a planetary nebula?

Interstellar gas from which planets are likely to form in the not-too-distant future.
Gas ejected from a low-mass star in the final stage of its life.
Gas created from the remains of planets that once orbited a dead star.
The remains of a high-mass star that has exploded.

Answer 24

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

Question 25

The ultimate fate of our Sun is to _____.

explode in a supernova
become a black hole
become a white dwarf that will slowly cool with time
become a rapidly spinning neutron star

Answer 25

become a white dwarf that will slowly cool with time

Question 26

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

a red giant
a main sequence star
a helium burning star
a main sequence star in a binary star system

Answer 26

a red giant

Question 27

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

These stars manufactured most of the carbon atoms in our bodies.
These stars manufactured virtually all the elements out of which we and our planet are made.
These stars generate the energy that makes life on Earth possible.
These stars provide most of the light that reaches us from globular clusters.

Answer 27

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

Question 28

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

hydrogen and deuterium
hydrogen and hydrogen
helium and helium
hydrogen and helium

Answer 28

helium and helium

Question 29

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

the Sun
a red giant star
a neutron star
a 10 solar mass star

Answer 29

a 10 solar mass star

Question 30

What is the CNO cycle?

a set of steps by which four hydrogen nuclei fuse into one helium nucleus
the set of fusion reactions that have produced all the carbon, nitrogen, and oxygen in the universe
the process by which helium is fused into carbon, nitrogen, and oxygen
the process by which carbon is fused into nitrogen and oxygen

Answer 30

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

Question 31

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
how much oxygen it now has in its core
its overall abundance of elements heavier than helium
its luminosity

Answer 31

its mass

Question 32

Why is iron significant to understanding how a supernova occurs?

The fusion of iron into uranium is the reaction that drives a supernova explosion.
Supernovae often leave behind neutron stars, which are made mostly of iron.
Iron is the heaviest of all atomic nuclei, and thus no heavier elements can be made.
Iron cannot release energy either by fission or fusion.

Answer 32

Iron cannot release energy either by fission or fusion.

Question 33

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

may be either a neutron star or a black hole
will always be a neutron star
may be either a white dwarf, neutron star, or black hole
will always be a black hole

Answer 33

may be either a neutron star or a black hole

Question 34

Why is Supernova 1987A particularly important to astronomers?

It was the first supernova detected in nearly 400 years.
It provided the first evidence that supernovae really occur.
It is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.
It occurred only a few light-years from Earth.

Answer 34

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

Question 35

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.
The two stars in a binary system should both be at the same stage of life; that is, they should either both be main sequence stars or both be subgiants.
It doesn't make sense to find a subgiant in a binary star system.
A star with a mass of 3.7 MSun is too big to be a main sequence star.

Answer 35

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

Question 36

Where does gold (the element) come from?

it was produced during the Big Bang
it is produced during the late stages of fusion in low-mass stars
it is produced during the supernova explosions of high-mass stars
it is produced by mass transfer in close binaries

Answer 36

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

Question 37

Our Sun is considered to be a ______.

intermediate-mass star
high-mass star
brown dwarf
low-mass star

Answer 37

low-mass star

Question 38

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
H-R diagrams of open clusters
spacecraft observations of the Sun
observing a low-mass star over many years

Answer 38

H-R diagrams of globular clusters

Question 39

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

The red giant is more massive.
Fusion reactions are producing energy at a greater rate in the red giant.
The red giant has a hotter core.
The red giant's surface is hotter.

Answer 39

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

Question 40

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

It is a subgiant that gradually grows dimmer as its hydrogen-burning shell expands and cools.
It is a red giant that grows in luminosity until it dies in a planetary nebula.
It is what is known as a helium-burning star, which has both helium fusion in its core and hydrogen fusion in a shell.
It is a subgiant that grows in luminosity until helium fusion begins in the central core.

Answer 40

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

Question 41

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

observing the structures of planetary nebulae
neutrino detections from nearby supernovae
decades of continuous monitoring of red giants in a globular cluster
studying the light rings around Supernova 1987A in the Large Magellanic Cloud

Answer 41

decades of continuous monitoring of red giants in a globular cluster

Question 42

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

Supernovae are more common.
They both occur in about equal numbers.
It is impossible to say.
Planetary nebula formation is more common.

Answer 42

Planetary nebula formation is more common.

Question 43

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

the cores of low-mass stars never contain significant amounts of carbon
carbon fusion can occur only in the stars known as carbon stars
the cores of low-mass stars never get hot enough for carbon fusion
only high-mass stars do fusion by the CNO cycle

Answer 43

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

Question 44

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

As each stage ends, the core shrinks and heats further.
Each successive stage lasts for approximately the same amount of time
As each stage ends, the reactions that occurred in previous stages continue in shells around the core.
Each successive stage creates an element with a higher atomic number and atomic mass number.

Answer 44

Each successive stage lasts for approximately the same amount of time

Question 45

Which event marks the beginning of a supernova?

The onset of helium burning after a helium flash.
The sudden collapse of an iron core into a compact ball of neutrons.
The sudden initiation of the CNO cycle.
The beginning of neon burning in an extremely massive star.

Answer 45

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

Question 46

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?

Because the supernova destroys the star, Betelgeuse would suddenly disappear from view.
Betelgeuse would suddenly appear to grow larger in size, soon reaching the size of the full Moon. It would also be about as bright as the full Moon.
We'd see a cloud of gas expanding away from the position where Betelgeuse used to be. Over a period of a few weeks, this cloud would fill our entire sky.
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.

Answer 46

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.

Question 47

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

Stars would be brighter.
Nuclear fusion could not power stars.
All stars would be red giants.
Stars would be less massive.

Answer 47

Nuclear fusion could not power stars.

Question 48

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?

This pattern in elemental abundances was apparently determined during the first few minutes after the Big Bang.
The apparent pattern is thought to be a random coincidence.
At the end of a high-mass star's life, it produces new elements through a series of helium capture reactions.
Elements with atomic mass numbers divisible by 4 tend to be more stable than elements in between.

Answer 48

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

Question 49

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

red supergiant
planetary nebula
protostar
supernova remnant

Answer 49

supernova remnant

Question 50

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

The two stars probably were once separate, but became a binary when a close encounter allowed their mutual gravity to pull them together.
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.
Although both stars probably formed from the same clump of gas, the more massive one must have had its birth slowed so that it became a main sequence stars millions of years later than its less massive companion.
The two stars are simply evolving normally and independently, and one has become a giant before the other.

Answer 50

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.

Question 51

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 are too massive to be affected by tidal forces.
Main sequence stars are too big to be affected by tidal forces.
Main sequence stars are unaffected by tidally-induced mass transfer.
Main sequence stars in a system like the Algol system are small compared to their physical separation.

Answer 51

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