Question 1

How much energy is released in the supernova explosion of a massive star?
A) Almost as much energy as the Sun emits over its entire lifetime
B) Almost as much energy as the entire Galaxy emits over its lifetime
C) As much energy as the Sun emits over its entire lifetime
D) 100 times as much energy as the Sun emits over its entire lifetime

Accepted Answer

A supernova explosion of a massive star releases approximately 100 times as much energy as the Sun emits over its entire lifetime. This is due to the enormous amount of gravitational potential energy that is converted into kinetic energy and radiation during the supernova explosion.

Question 2

Which of the following will a high-mass star NOT do at or near the end of its life?
A) Emit copious amounts of neutrinos
B) Eject its outer layers and become a neutron star
C) Eject its outer layers and become a white dwarf
D) Convert silicon into iron in its core

Accepted Answer

A high-mass star will undergo a supernova explosion and either become a black hole or a neutron star, but it will not become a white dwarf.

Question 3

A typical supernova,in the hours following its explosion,is as bright as
A) 1000 typical spiral galaxies.
B) an entire galaxy.
C) 1000 Sun-like stars.
D) a million Sun-like stars.

Accepted Answer

A typical supernova, in the hours following its explosion, can shine as brightly as an entire galaxy, thanks to the immense amount of energy released. This makes it one of the most luminous events in the universe, observable across great distances.

Question 4

Which of the following is NEVER a consequence of a supernova explosion?
A) Condensation of matter into a solid nuclear star composed entirely of neutrons
B) Triggering of star formation by shock waves moving through interstellar space
C) Formation of a planetary nebula
D) Manufacture of the nuclei of heavy elements

Accepted Answer

A planetary nebula is formed at the end of a star's life when it expels its outer layers, whereas a supernova explosion happens when a very massive star has exhausted all its fuel and collapses in on itself, triggering a massive explosion. Planetary nebulae are not a consequence of supernova explosions.

Question 5

When a supernova explosion results from core collapse in a massive star it appears to leave behind
A) a rapidly expanding shell of gas and a central neutron star or black hole.
B) a rapidly rotating shell of gas,dust,and radiation,but no central object.
C) a rapidly expanding shell of gas and a compact white-dwarf star at its center.
D) nothing,the explosion changes all the matter completely into energy,which then radiates into space at the speed of light.

Accepted Answer

When a supernova explosion results from core collapse in a massive star, it leaves behind a rapidly expanding shell of gas and a central neutron star or black hole. The explosion blows off the outer layers of the star, leaving the core exposed. The core collapses under its own gravity and forms either a neutron star or a black hole, while the outer layers of the star are expelled into space as a rapidly expanding shell of gas.

Question 6

Which nuclear fusion cycle follows the helium fusion phase as a massive star evolves?
A) Silicon "burning"
B) Carbon "burning"
C) Iron "burning"
D) Oxygen "burning"

Accepted Answer

After helium fusion, a massive star will undergo carbon fusion, also known as carbon "burning".

Question 7

For a massive star,core hydrogen burning lasts for several million years.In contrast,core silicon burning lasts for only about
A) 1 day.
B) 1 minute.
C) 600 years.
D) 1 year.

Accepted Answer

Core silicon burning in a massive star is a very rapid process, lasting for only about a day before the star undergoes a supernova explosion.

Question 8

The capture of free neutrons by heavy atomic nuclei is
A) easy because neutron capture always produces a stable product nucleus.
B) easy because the neutron has no electric charge.
C) difficult,unless the nucleus is already unstable.
D) difficult,unless the neutron is moving rapidly.

Accepted Answer

Neutrons have no electric charge, which means they are not repelled by the positively charged nucleus. This makes neutron capture relatively easy. The other answer choices are incorrect. A) Neutron capture does not always produce a stable product nucleus. B) The stability of the nucleus is not the primary factor in neutron capture. C) Neutron capture can occur with stable nuclei. D) The speed of the neutron may affect the probability of capture, but it is not necessary for capture to occur.

Question 9

The supergiant stars Betelgeuse and Rigel in the Orion region of the sky appear particularly bright because
A) they are in a region of low interstellar medium density and,therefore,are not heavily obscured compared to equivalent stars elsewhere.
B) they are close in our spiral arm.
C) they are very luminous.
D) their high surface temperatures make them easy to see,even though they are intrinsically faint and far away,because most of their light is concentrated in the visible range.

Accepted Answer

Betelgeuse and Rigel are supergiant stars, which means they are highly luminous and have a large radius. This makes them appear particularly bright in the sky, even though they are relatively far away.

Question 10

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon,oxygen,and so forth,into heavier elements AND generate excess energy,until iron has been produced.Why is it not possible for fusion reactions to release energy from iron nuclei?
A) It has been found that iron nuclei never undergo fusion reactions.
B) The magnetic properties of iron produce extra repulsion that,along with the electrostatic repulsion,prevents fusion of iron nuclei with protons.
C) Iron is the heaviest possible element in nature,and fusion of heavier elements is not possible.
D) The electrostatic repulsion between the iron nucleus and the proton is so great that fusion requires extra energy,rather than releasing it.

Accepted Answer

The electrostatic repulsion between the iron nucleus and the proton is so great that fusion requires extra energy, rather than releasing it. This means that it takes more energy to fuse iron nuclei than is released in the process, making it impossible for fusion reactions to release energy from iron nuclei.

Question 11

The majority of massive stars,at the point in time when they explode as supernovae,have become
A) red supergiants.
B) neutron stars.
C) blue supergiants.
D) white dwarfs.

Accepted Answer

The majority of massive stars, at the point in time when they explode as supernovae, have evolved to become red supergiants. This is because these stars have exhausted their nuclear fuel in their cores, causing the core to contract and heat up, which leads to the outer layers of the star expanding and cooling, resulting in a red supergiant phase. Eventually, the star will undergo a rapid collapse and rebound, leading to a supernova explosion.

Question 12

At the end of the life of a massive star,during the process of core collapse,the time taken from the start of collapse to the attainment of nuclear density is about
A) 1/4 second.
B) 1/2000 second.
C) 8 minutes.
D) a few hours.

Accepted Answer

During the process of core collapse in a massive star, the time taken from the start of collapse to the attainment of nuclear density is very short, on the order of fractions of a second. The collapse is very rapid and leads to a supernova explosion. Option A) 1/4 second is the best choice as it falls within this time frame. B) 1/2000 second, C) 8 minutes, and D) a few hours are all much longer than the actual time taken for core collapse.

Question 13

The core collapse phase at the end of the life of a massive star is triggered when
A) the helium flash and thermal pulses have expelled the star's envelope.
B) nuclear fusion has produced a significant amount of iron in its core.
C) the core becomes as dense as an atomic nucleus.
D) the density reaches a threshold at which electron degeneracy pressure begins to play a role.

Accepted Answer

The core collapse phase in a massive star's life is triggered when nuclear fusion in the core has produced a significant amount of iron. Iron fusion consumes energy rather than releasing it, leading to a loss of pressure support and eventual collapse of the core.

Question 14

Which force induces the core to condense and collapse in massive stars at the conclusion of each episode of nuclear fusion,such as the carbon,oxygen,and silicon fusion cycles?
A) Gravity
B) The nuclear attractive force between nuclei and between neutrons and protons
C) Gas pressure produced by the very high gas temperatures
D) Electron degeneracy pressure

Accepted Answer

Gravity is the force that induces the core to condense and collapse in massive stars at the conclusion of each episode of nuclear fusion. As the star runs out of fuel, there is no longer enough fusion energy being produced to counteract the force of gravity, which leads to the collapse of the core. This collapse can ultimately result in a supernova explosion.

Question 15

During the late stages of evolution (e.g. ,oxygen burning)in massive stars,nuclear reactions produce many free neutrons.What very important effect do these neutrons have on the composition of the star?
A) The neutrons,being uncharged,escape from the star,thus carrying away energy from the core of the star and lowering its temperature.
B) The neutrons are captured by atomic nuclei and can produce heavy elements that would not form from nuclear fusion alone.
C) The neutrons are captured by atomic nuclei,causing the nuclei to split by fission reactions into lighter elements that would otherwise be very rare in the universe.
D) The neutrons decay into protons and electrons,thus increasing the amount of hydrogen in the core and extending the life of the star.

Accepted Answer

Free neutrons can be captured by atomic nuclei, causing them to become heavier and producing elements beyond iron that cannot be formed through nuclear fusion alone. This process is known as neutron capture or the r-process (rapid neutron capture), and it is responsible for the formation of many heavy elements found in the universe.

Question 16

What is the source of energy that allowed supernova 1987A to continue to brighten slowly for a few months after its initial explosion?
A) Radioactive decay of specific nuclei produced in the explosion
B) Thermonuclear reactions between iron nuclei and protons,neutrons,and helium nuclei
C) Thermonuclear reactions between hydrogen nuclei in the shell of gas surrounding the supernova,triggered by the shock wave from the explosion
D) Slow gravitational compression of the remnant core of the supernova and the consequent release of gravitational potential energy

Accepted Answer

The source of energy that allowed supernova 1987A to continue to brighten slowly for a few months after its initial explosion was the radioactive decay of specific nuclei produced in the explosion. As these nuclei decayed, they released energy that continued to power the brightness of the supernova.

Question 17

Where are core-collapse supernovae detected?
A) Only in spiral galaxies,never in ellipticals
B) In our Galaxy and many others
C) Only in our Galaxy
D) Only in elliptical galaxies,never in spirals

Accepted Answer

Core-collapse supernovae are detected in our Galaxy and many others. They are more common in spiral galaxies, but also occur in elliptical galaxies.

Question 18

Ancient Chinese astronomers recorded the appearance of what phenomenon in 1054 A.D.?
A) A nearby nova explosion in a nearby galaxy
B) A brilliant auroral display covering the whole Earth
C) A supernova,visible in daylight,within our Galaxy
D) A bright binary star undergoing eclipse

Accepted Answer

Ancient Chinese astronomers recorded the appearance of a supernova, visible in daylight, within our Galaxy in 1054 A.D. This supernova is now known as SN 1054 and is located in the constellation Taurus.

Question 19

A sequence of thermonuclear fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon,oxygen,and so forth,into heavier nuclei AND also generate excess energy,up to a limit beyond which no further energy-producing reactions can occur.The element that is produced when this limit is reached is
A) lead.
B) oxygen.
C) uranium.
D) iron.

Accepted Answer

The limit at which no further energy-producing reactions can occur is when the fusion process reaches the production of iron. This is because iron has the highest binding energy per nucleon, meaning that it takes more energy to fuse an iron nucleus than it releases, making it energetically unfavorable to continue fusion beyond this point. Therefore, the answer is D) iron.

Question 20

An old high-mass star can have a number of shells (hydrogen,helium,carbon,neon,oxygen,silicon)plus an iron core.Fusion generally takes place everywhere EXCEPT in the
A) hydrogen shell.
B) helium shell.
C) silicon shell.
D) iron core.

Accepted Answer

Fusion reactions cannot take place in the iron core of a high-mass star because it requires energy for fusion to occur at that point, whereas other shells have enough energy to undergo fusion. Additionally, the fusion of iron does not produce any net energy, so fusion reactions cease entirely in the star once the iron core forms.

Quiz 12: Predicting the Violent End of the Largest Stars

How much energy is released in the supernova explosion of a massive star?

Which of the following will a high-mass star NOT do at or near the end of its life?

A typical supernova,in the hours following its explosion,is as bright as

Which of the following is NEVER a consequence of a supernova explosion?

When a supernova explosion results from core collapse in a massive star it appears to leave behind

Which nuclear fusion cycle follows the helium fusion phase as a massive star evolves?

For a massive star,core hydrogen burning lasts for several million years.In contrast,core silicon burning lasts for only about

The capture of free neutrons by heavy atomic nuclei is

The supergiant stars Betelgeuse and Rigel in the Orion region of the sky appear particularly bright because

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon,oxygen,and so forth,into heavier elements AND generate excess energy,until iron has been produced.Why is it not possible for fusion reactions to release energy from iron nuclei?

The majority of massive stars,at the point in time when they explode as supernovae,have become

At the end of the life of a massive star,during the process of core collapse,the time taken from the start of collapse to the attainment of nuclear density is about

The core collapse phase at the end of the life of a massive star is triggered when

Which force induces the core to condense and collapse in massive stars at the conclusion of each episode of nuclear fusion,such as the carbon,oxygen,and silicon fusion cycles?

During the late stages of evolution (e.g. ,oxygen burning) in massive stars,nuclear reactions produce many free neutrons.What very important effect do these neutrons have on the composition of the star?

What is the source of energy that allowed supernova 1987A to continue to brighten slowly for a few months after its initial explosion?

Where are core-collapse supernovae detected?

Ancient Chinese astronomers recorded the appearance of what phenomenon in 1054 A.D.?

An old high-mass star can have a number of shells (hydrogen,helium,carbon,neon,oxygen,silicon) plus an iron core.Fusion generally takes place everywhere EXCEPT in the