Question 1

The luminosity of a Type II supernova ________ with time.

Accepted Answer

A)  increases only 
B)  decreases only 
C)  first increases, then decreases 
D)  first decreases, then increases 
E)  is a constant value 
A)  increases only 
B)  decreases only 
C)  first increases, then decreases 
D)  first decreases, then increases 
E)  is a constant value

Question 2

What is the reason for the very fast rotation of neutron stars?

Accepted Answer

A)  It is a consequence of the conservation of angular momentum applied to collapsing objects. 
B)  The convection in the cores of high-mass stars is responsible for this. 
C)  The high temperature in the cores of high-mass stars imprints fast rotations. 
D)  The degenerate iron core leads to fast spins. 
E)  The fast rotation is due to their huge gravity on their surface. 
A)  It is a consequence of the conservation of angular momentum applied to collapsing objects. 
B)  The convection in the cores of high-mass stars is responsible for this. 
C)  The high temperature in the cores of high-mass stars imprints fast rotations. 
D)  The degenerate iron core leads to fast spins. 
E)  The fast rotation is due to their huge gravity on their surface.

Question 3

In a rescaled model in which the Crab Nebula (10 light-years across in reality) would only be about 10 km across, how big would the central neutron star (about 10 km in reality) be?

Accepted Answer

A)  the size of football field 
B)  the size of an aspirin 
C)  the size of a football 
D)  the size of an atom 
E)  the size of the tip of a ballpoint pen 
A)  the size of football field 
B)  the size of an aspirin 
C)  the size of a football 
D)  the size of an atom 
E)  the size of the tip of a ballpoint pen

Question 4

An iron core cannot support a massive main-sequence star because iron

Accepted Answer

A)  has low nuclear binding energy. 
B)  is not present in stellar interiors. 
C)  supplies too much pressure. 
D)  fusion occurs only in a degenerate core. 
E)  cannot generate energy when fusing heavier nuclei. 
A)  has low nuclear binding energy. 
B)  is not present in stellar interiors. 
C)  supplies too much pressure. 
D)  fusion occurs only in a degenerate core. 
E)  cannot generate energy when fusing heavier nuclei.

Question 5

Which of these fusion reactions begins first in the core of a massive star?

Accepted Answer

A)  silicon fusion to iron 
B)  neon fusion to magnesium 
C)  carbon fusion to neon 
D)  helium fusion to carbon 
E)  hydrogen fusion to helium 
A)  silicon fusion to iron 
B)  neon fusion to magnesium 
C)  carbon fusion to neon 
D)  helium fusion to carbon 
E)  hydrogen fusion to helium

Question 6

Betelgeuse is a star whose luminosity exceeds 1.2 * 105 LSUN, but its measured surface temperature is quite low for a star, about 3500K.What would be its estimated size and where would it fall in the H-R diagram shown in the figure below? What would be the final fate of Betelgeuse?

Accepted Answer

The parameters given for Betelgeuse woul

Question 7

Why does the luminosity of a high-mass star remain nearly constant as the star burns elements heavier than helium in its core, even though it is producing millions of times more
Energy per second than it did on the main sequence?

Accepted Answer

A)  Most of the energy is trapped in the core, increasing the core's temperature. 
B)  All of the extra energy goes into heating the shells of fusion surrounding the core. 
C)  Most of the energy is absorbed by the outer layers of the star, increasing the star's radius but leaving its luminosity unchanged. 
D)  Most of the energy is carried out of the star by escaping neutrinos. 
E)  All of the energy goes into breaking apart light elements such as helium and carbon. 
A)  Most of the energy is trapped in the core, increasing the core's temperature. 
B)  All of the extra energy goes into heating the shells of fusion surrounding the core. 
C)  Most of the energy is absorbed by the outer layers of the star, increasing the star's radius but leaving its luminosity unchanged. 
D)  Most of the energy is carried out of the star by escaping neutrinos. 
E)  All of the energy goes into breaking apart light elements such as helium and carbon.

Question 8

The main-sequence lifetime of a star can be estimated using the formula:   What is the lowest-mass star that can have left the main sequence, assuming this star was created as soon as the universe formed? (The universe is about 13.8 billion years old.)

Accepted Answer

We need to solve the given equation for

Question 9

The dominant mechanism by which high-mass stars generate energy on the main sequence is called

Accepted Answer

A)  the proton-proton chain. 
B)  the carbon-carbon reaction. 
C)  the triple-alpha process. 
D)  the CNO cycle. 
E)  neutrino cooling. 
A)  the proton-proton chain. 
B)  the carbon-carbon reaction. 
C)  the triple-alpha process. 
D)  the CNO cycle. 
E)  neutrino cooling.

Question 10

What should be true about the oldest stars in the Milky Way?

Accepted Answer

A)  They would have lots of heavy elements because they have been around for a long time and have undergone a lot of nucleosynthesis in their cores. 
B)  They would be seen as supergiants. 
C)  They would have few heavy elements because there was not much chance for earlier generations of stars to explode as supernovae before these stars were formed. 
D)  They would be massive because they were among the first stars formed. 
E)  They would likely be seen as pulsars. 
A)  They would have lots of heavy elements because they have been around for a long time and have undergone a lot of nucleosynthesis in their cores. 
B)  They would be seen as supergiants. 
C)  They would have few heavy elements because there was not much chance for earlier generations of stars to explode as supernovae before these stars were formed. 
D)  They would be massive because they were among the first stars formed. 
E)  They would likely be seen as pulsars.

Question 11

A H-R diagram is made for two star clusters, Cluster A and Cluster B.Cluster A has stars of spectral type A, while Cluster B has no such stars.What can we conclude about these two clusters from this information?

Accepted Answer

A)  Cluster A has more total stars than Cluster B. 
B)  Cluster A is more distant than Cluster B. 
C)  Cluster A has less iron present than Cluster B. 
D)  Cluster A is younger than Cluster B. 
E)  Nothing can be determined without more information. 
A)  Cluster A has more total stars than Cluster B. 
B)  Cluster A is more distant than Cluster B. 
C)  Cluster A has less iron present than Cluster B. 
D)  Cluster A is younger than Cluster B. 
E)  Nothing can be determined without more information.

Question 12

Give two major arguments for the scarcity of stars in the high-mass, high-luminosity, main-sequence blue region of the H-R diagram.

Accepted Answer

Firstly,only a very small number of high

Question 13

Neutron stars have masses that range from

Accepted Answer

A)  3.5 MSUN to 25 MSUN. 
B)  1.2 MSUN to 30 MSUN. 
C)  2.5 MSUN to 10 MSUN. 
D)  1.4 MSUN to 2 MSUN. 
E)  0.1 MSUN to 1.4 MSUN. 
A)  3.5 MSUN to 25 MSUN. 
B)  1.2 MSUN to 30 MSUN. 
C)  2.5 MSUN to 10 MSUN. 
D)  1.4 MSUN to 2 MSUN. 
E)  0.1 MSUN to 1.4 MSUN.

Question 14

What mechanism provides the internal pressure inside a neutron star?

Accepted Answer

A)  ordinary pressure from hydrogen and helium gas 
B)  degeneracy pressure from neutrons 
C)  degeneracy pressure from electrons 
D)  rapid rotation 
E)  strong magnetic fields 
A)  ordinary pressure from hydrogen and helium gas 
B)  degeneracy pressure from neutrons 
C)  degeneracy pressure from electrons 
D)  rapid rotation 
E)  strong magnetic fields

Question 15

Why are star clusters helpful for testing our ideas about star formation and stellar evolution?

Accepted Answer

Stellar clusters constitute ideal "labor

Question 16

Once silicon burning initiates in the core of a high-mass star, the star has only a few ________ left to live.

Accepted Answer

A)  seconds 
B)  days 
C)  months 
D)  years 
E)  million years 
A)  seconds 
B)  days 
C)  months 
D)  years 
E)  million years

Question 17

How do astronomers know that the Sun (and our Solar System) formed from the remnants of other stars?

Accepted Answer

A)  The Sun acts like a low-mass star and a high-mass star at the same time. 
B)  Elements heavier than hydrogen and helium must have formed within other stars and then were ejected into space by supernovae. 
C)  Radioactive carbon could only form in the core of a high-mass star. 
D)  Jupiter shows signs of having been a main-sequence star at one point. 
E)  Evidence shows that the asteroids and comets must have formed around stars with different spectral types than the Sun. 
A)  The Sun acts like a low-mass star and a high-mass star at the same time. 
B)  Elements heavier than hydrogen and helium must have formed within other stars and then were ejected into space by supernovae. 
C)  Radioactive carbon could only form in the core of a high-mass star. 
D)  Jupiter shows signs of having been a main-sequence star at one point. 
E)  Evidence shows that the asteroids and comets must have formed around stars with different spectral types than the Sun.

Question 18

A few hours before a high-mass star will blast its outer layers in a colossal explosion, specialized detectors on Earth would recognize a spike in the number of

Accepted Answer

A)  iron nuclei. 
B)  carbon nuclei. 
C)  protons. 
D)  neutrinos. 
E)  aurorae. 
A)  iron nuclei. 
B)  carbon nuclei. 
C)  protons. 
D)  neutrinos. 
E)  aurorae.

Question 19

The CNO cycle is the more efficient mechanism for hydrogen fusion only in stars more massive than 1.3-1.5 MSUN because of the greater ________ their cores.

Accepted Answer

A)  concentration of heavy elements like carbon in 
B)  turbulence in 
C)  abundance of hydrogen in 
D)  temperature of 
E)  rotation speed of 
A)  concentration of heavy elements like carbon in 
B)  turbulence in 
C)  abundance of hydrogen in 
D)  temperature of 
E)  rotation speed of

Question 20

In their post-main-sequence stages of evolution high-mass stars spend progressively shorter periods in each stage, in part because

Accepted Answer

A)  they are losing energy faster as neutrino cooling becomes more important. 
B)  stellar cores become permanently inert once the stars leaves the main sequence. 
C)  the stars switch from fusion to fission to produce energy. 
D)  massive stars lose most of their nuclear fuel through powerful stellar winds. 
E)  the energy is now produced only via violent gravitational contractions. 
A)  they are losing energy faster as neutrino cooling becomes more important. 
B)  stellar cores become permanently inert once the stars leaves the main sequence. 
C)  the stars switch from fusion to fission to produce energy. 
D)  massive stars lose most of their nuclear fuel through powerful stellar winds. 
E)  the energy is now produced only via violent gravitational contractions.

Exam 17: Evolution of High-Mass Stars

The luminosity of a Type II supernova ________ with time.

What is the reason for the very fast rotation of neutron stars?

In a rescaled model in which the Crab Nebula (10 light-years across in reality) would only be about 10 km across, how big would the central neutron star (about 10 km in reality) be?

An iron core cannot support a massive main-sequence star because iron

Which of these fusion reactions begins first in the core of a massive star?

Betelgeuse is a star whose luminosity exceeds 1.2 * 105 LSUN, but its measured surface temperature is quite low for a star, about 3500K.What would be its estimated size and where would it fall in the H-R diagram shown in the figure below? What would be the final fate of Betelgeuse?

Why does the luminosity of a high-mass star remain nearly constant as the star burns elements heavier than helium in its core, even though it is producing millions of times more Energy per second than it did on the main sequence?

The main-sequence lifetime of a star can be estimated using the formula: What is the lowest-mass star that can have left the main sequence, assuming this star was created as soon as the universe formed? (The universe is about 13.8 billion years old.)

The dominant mechanism by which high-mass stars generate energy on the main sequence is called

What should be true about the oldest stars in the Milky Way?

A H-R diagram is made for two star clusters, Cluster A and Cluster B.Cluster A has stars of spectral type A, while Cluster B has no such stars.What can we conclude about these two clusters from this information?

Give two major arguments for the scarcity of stars in the high-mass, high-luminosity, main-sequence blue region of the H-R diagram.

Neutron stars have masses that range from

What mechanism provides the internal pressure inside a neutron star?

Why are star clusters helpful for testing our ideas about star formation and stellar evolution?

Once silicon burning initiates in the core of a high-mass star, the star has only a few ________ left to live.

How do astronomers know that the Sun (and our Solar System) formed from the remnants of other stars?

A few hours before a high-mass star will blast its outer layers in a colossal explosion, specialized detectors on Earth would recognize a spike in the number of

The CNO cycle is the more efficient mechanism for hydrogen fusion only in stars more massive than 1.3-1.5 MSUN because of the greater ________ their cores.

In their post-main-sequence stages of evolution high-mass stars spend progressively shorter periods in each stage, in part because

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Betelgeuse is a star whose luminosity exceeds 1.2 * 10⁵L_SUN, but its measured surface temperature is quite low for a star, about 3500K.What would be its estimated size and where would it fall in the H-R diagram shown in the figure below? What would be the final fate of Betelgeuse?

The CNO cycle is the more efficient mechanism for hydrogen fusion only in stars more massive than 1.3-1.5 M_SUN because of the greater ________ their cores.