Deck 21: Stellar Explosions: Novae,Supernovae,and the Formation of the Elements

Question 1

Because they all involve formation of iron in cores of massive stars,all type II supernovae are equally luminous.

Answer 1

False

Question 2

Because they all involve the detonation of a carbon-rich white dwarf at Chandrasekhar's limit,all type I supernovae are equally luminous.

Answer 2

True

Question 3

Type II supernovae have little hydrogen in their spectra; it had been used up already.

Answer 3

False

Question 4

It takes less and less time to fuse heavier and heavier elements inside a high mass star.

Question 5

A carbon-detonation supernova starts out as a white dwarf in a close binary system.

Question 6

Iron nuclei are the most tightly bound nuclei,which is why their production leads to type II supernovae.

Question 7

Once carbon is formed in massive star cores,the majority of nuclei formed from then on will belong to even numbered elements,due to addition to more helium nuclei as alpha particles.

Question 8

Two isotopes of the same element differ only in the number of protons.

Question 9

Stellar nucleosynthesis is responsible for the existence of all elements except hydrogen.

Question 10

A Type I supernova involves the collapsing core of a high mass star.

Question 11

Novae are more closely related to type II than to type I supernovae.

Question 12

A recurring nova could eventually explode as a Type I supernova.

Question 13

Most of the energy released during a supernova is emitted as neutrinos.

Question 14

A massive star can fuse only up to the element silicon in its core.

Question 15

The spectra of the youngest stars show the most heavy elements present.

Question 16

Unlike supernovae,novae can explode more than once,increasing their luminosity by thousands of times.

Question 17

Iron is the most stably bonded atomic nucleus.

Question 18

The final core collapse of a massive star takes about 13 seconds.

Question 19

Except for hydrogen and most of the helium,all the elements have been formed through stellar nucleosynthesis.

Question 20

Novae always occur in a close binary star system.

Question 21

A 20 solar mass star will stay on the main sequence for 10 million years,yet its iron core can exist for only a:

A) day.
B) week.
C) month.
D) year.
E) century.

Question 22

Most of the energy of the supernova is carried outward via a flood of:

A) gamma rays.
B) helium nuclei.
C) protons.
D) neutrinos.
E) positrons.

Question 23

What evidence is there that supernovae really have occurred?

A) Crab Nebula
B) supernova remnants
C) existence of heavy radioactive elements in nature
D) observations of the actual explosions
E) All of the above.

Question 24

What made supernova 1987a so useful to study?

A) We saw direct evidence of nickel to iron decay in its light curve.
B) Its progenitor had been observed previously.
C) In the Large Magellanic Cloud, we already knew its distance.
D) It occurred after new telescopes, such as Hubble, could observe it very closely.
E) All of the above are correct.

Question 25

The core of a highly evolved high mass star is a little larger than:

A) our solar system.
B) our Sun.
C) Jupiter.
D) Earth.
E) a white dwarf.

Question 26

The supernova that formed M-1,the Crab Nebula,was observed in:

A) 1572 AD by Tycho Brahe.
B) 1604 AD by Johannes Kepler.
C) 1054 AD by Chinese and Middle Eastern astronomers.
D) 1006 by observers in the southern hemisphere.
E) about 9,000 BC by all our ancestors.

Question 27

Where was supernova 1987a located?

A) in the Orion Nebula, M-42
B) in Sagittarius, near the Galactic Nucleus
C) in our companion galaxy, the Large Magellanic Cloud
D) in M-13, one of the closest of the evolved globular clusters
E) near the core of M-31, the Andromeda Galaxy

Question 28

For a nova to occur,the system must have already been a(n):

A) astrometric binary.
B) detached binary.
C) spectroscopic binary.
D) mass-transfer binary.
E) eclipsing binary.

Question 29

At temperatures of ________ K,photons can split apart nuclei until only protons and neutrons are left in photodisintegration.

A) ten million
B) 100 million
C) one billion
D) ten billion
E) one hundred billion

Question 30

The element with the most stable nucleus and smallest mass per particle is:

A) uranium.
B) argon.
C) helium.
D) hydrogen
E) iron.

Question 31

A surface explosion on a white dwarf,caused by falling matter from the atmosphere of its binary companion,creates what kind of object?

A) hypernova
B) nova
C) gamma ray burstar
D) type I supernova
E) type II supernova

Question 32

The Chandrasekhar mass limit is:

A) 0.08 solar masses.
B) 0.4 solar masses.
C) 1.4 solar masses.
D) 3 solar masses.
E) 8 solar masses.

Question 33

In neutronization of the core,a proton and an electron make a neutron and a(n):

A) positron.
B) muon.
C) neutrino.
D) pion.
E) antineutron.

Question 34

An iron core cannot support a star because:

A) iron is the heaviest element, and sinks upon differentiation.
B) iron has poor nuclear binding energy.
C) iron cannot fuse with other nuclei to produce energy.
D) iron supplies too much pressure.
E) iron is in the form of a gas, not a solid, in the center of a star.

Question 35

When a stellar iron core collapses,large numbers of neutrinos are formed,and then:

A) they form the neutron star.
B) they are absorbed by electrons to produce positrons.
C) they are captured to form heavy elements.
D) they are captured to form light elements.
E) they immediately pass through the core and escape to space.

Question 36

As a star's evolution approaches the Type II supernova,we find:

A) the heavier the element, the less time it takes to make it.
B) the heavier the element, the higher the temperature to fuse it.
C) helium to carbon fusion takes at least 100 million K to start.
D) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova.
E) All of the above are correct.

Question 37

A star can be a supernova:

A) in predictable cycles of decades.
B) a few times, at unpredictable intervals.
C) only if it can fuse iron in its core.
D) before it reaches the main sequence, if it is massive enough.
E) only once.

Question 38

Why are neutrinos from a type II supernova detected before photons?

A) Neutrinos travel faster than photons.
B) Neutrinos are easier to detect than photons.
C) Neutrinos are produced in the explosion before photons.
D) Neutrinos are emitted from the outer part of the star; photons come from the core.
E) Neutrinos escape from the star quickly because they hardly interact with matter; photons are delayed by interactions with matter.

Question 39

The total energy emitted by the brightest nova explosions is about:

A) 1,000 Suns.
B) 50,000 Suns.
C) a million Suns.
D) a billion Suns.
E) a trillion Suns.

Question 40

Beyond the formation of iron,nuclear energy can be produced only by:

A) fusion of still heavier elements.
B) ionization of the radioactive nuclei.
C) fission of heavy nuclei back toward lighter ones.
D) gravity.
E) the dark force.

Question 41

Supernova remnants differ from star forming regions because,although there is ionized hydrogen in both,supernova remnants:

A) don't look like star forming regions.
B) are much bigger than star forming regions.
C) are located far from star forming regions.
D) are more diffuse than star forming regions.
E) contain no ionizing stars.

Question 42

An object in the sky brightens suddenly,but shows no hydrogen lines in its spectrum.It is most likely a(n):

A) comet.
B) type I supernova.
C) type II supernova.
D) asteroid impact.
E) stellar collision.

Question 43

The heaviest nuclei of all are formed:

A) by neutron capture during a type II supernova explosion.
B) during a nova explosion.
C) during a carbon detonation supernova.
D) during carbon burning in the giant stage.
E) during the triple alpha process.

Question 44

If a white dwarf gains sufficient mass,it can become a:

A) brown dwarf.
B) type II supernova.
C) type I supernova.
D) planetary nebula.
E) black dwarf.

Question 45

In order of visual luminosity at the start,which is most luminous?

A) a red supergiant
B) a planetary nebula
C) a nova
D) a type I supernova
E) a type II supernova

Question 46

Which of these events is NOT possible?

A) low-mass stars swelling up to produce planetary nebulae
B) red giants exploding as Type II supernovae
C) close binary stars producing recurrent novae explosions
D) white dwarfs and companion stars producing recurrent Type I supernova events
E) a white dwarf being found in the center of a planetary nebula

Question 47

Which of these is the likely progenitor of a type I supernova?

A) a mass-transfer binary, with the white dwarf already at 1.3 solar masses
B) a contact binary, with the neutron star at 2.3 solar masses
C) an evolved red giant which is just starting to make silicon in its core
D) an evolved blue supergiant that is about to experience the helium flash
E) a helium-neon white dwarf

Question 48

Which of these does NOT depend on a close binary system to occur?

A) a nova
B) a Type I supernova
C) a Type II supernova
D) All of these need mass transfer to occur.
E) None of these depend on mass transfer.

Question 49

What produces a type-I supernova?

A) the collapse of the core of a massive star
B) the helium flash blows apart a giant's core
C) mass transfer onto a white dwarf pushing it over 1.4 solar masses
D) a nova igniting a helium flash in its red giant companion
E) the radioactive decay of nickel 56 into cobalt 56 into iron 56

Question 50

What is the amount of energy emitted in the form of neutrinos,during a supernova explosion,compared to the amount of energy radiated as electromagnetic radiation?

A) only .007 as much
B) about equal amounts
C) about twice as much
D) ten times more
E) 100 times more

Question 51

Type I supernovae are NOT:

A) products of mass transfer.
B) created by the mass of the white dwarf exceeding Chandrasekhar's Limit.
C) rich in hydrogen from the outer envelope of the collapsed star.
D) brighter than type II supernovae.
E) created by carbon detonation.

Question 52

Which of these is the likely progenitor of a type II supernova?

A) a mass-transfer binary, with the white dwarf already at 1.3 solar masses
B) a contact binary, with the neutron star at 2.3 solar masses
C) an evolved red giant which is just starting to make silicon in its core
D) two white dwarfs in a contact binary system
E) an evolved blue supergiant that is about to experience the helium flash

Question 53

When observing a star that increases dramatically in brightness,if a plateau is observed in the light curve during the declining phase,the event is probably:

A) a nova.
B) a type I supernova.
C) a type II supernova.
D) fusion in an accretion disk around a white dwarf.
E) fusion in an accretion disk around a neutron star.

Question 54

Which of these is NOT true about supernovae?

A) Type I involves carbon detonation.
B) Type II involves formation of iron in the core.
C) The two types are both closely related to evolution of white dwarfs.
D) The one in 1987 in the Large Magellanic Cloud was of type II.
E) Neutronization is vital in understanding type II core collapse.

Question 55

What can you conclude about a Type I supernova?

A) It was originally a low-mass star.
B) It was originally a high mass star.
C) Its spectrum will show large amounts of hydrogen.
D) Its core was mostly iron.
E) The star never reached the Chandrasekhar Limit.

Question 56

Nearly all the elements found in nature were formed inside stars,EXCEPT for:

A) carbon and silicon.
B) hydrogen and helium.
C) helium and carbon.
D) silver and technetium.
E) uranium and radium.

Question 57

A recurrent nova could eventually build up to a:

A) planetary nebula.
B) type I supernova.
C) type II supernova.
D) hypernova.
E) quasar.

Question 58

For a white dwarf to explode entirely as a Type I supernova,its mass must be:

A) at least 0.08 solar masses.
B) 1.4 solar masses, the Chandrasekhar Limit.
C) 3 solar masses, the Schwartzschild Limit.
D) 20 solar masses, the Hubble Limit.
E) 100 solar masses, the most massive known stars.

Question 59

What is stellar nucleosynthesis?

A) the formation of heavier elements inside stars
B) the formation of planetary nebulae by red giants
C) the formation of stars from a nucleus of contracting material
D) the formation of white dwarfs, neutron stars, and black holes from stars
E) the process by which stars form interstellar dust

Question 60

The Chandrasekhar Limit is:

A) the upper mass limit for a white dwarf.
B) the temperature at which hydrogen fusion starts.
C) the temperature at which helium fusion starts.
D) the point at which a planetary nebula forms.
E) the lower mass limit for a Type II supernova.

Question 61

Which type of heavy atomic nuclei are most common,and why?

A) Transuranium elements, for only very heavy elements are made in supernovae.
B) Odd numbered elements, because hydrogen is the building block for all heavier elements.
C) Even numbered elements, for helium is "giant food" for everything beyond itself.
D) Metals, for iron is the last abundant element formed before the type II supernova.
E) Noble gases, for they are the most stable elements.

Question 62

The heaviest nuclei of all are formed:

A) in the horizontal branch.
B) in dense white dwarfs.
C) during nova explosions.
D) in the ejection of matter in the planetary nebula.
E) in the core collapse that set the stage of type II supernovae.

Question 63

Type I supernovae result from ________ stars which have accreted sufficient additional mass via mass transfer from a close binary companion.

Question 64

Which statement about young stars is FALSE?

A) They contain a larger fraction of heavy elements than previous generations.
B) They are born in a dustier environment than earlier generations.
C) They are more likely to have planets forming with them than earlier generations.
D) The high mass stars will be more likely to produce heavier elements as they evolve.
E) Being young, they will have more pure hydrogen than earlier generations.

Question 65

The alpha process tends to produce chiefly:

A) only carbon.
B) stable elements.
C) even numbered elements.
D) odd numbered elements.
E) only radioactive elements.

Question 66

Which statement about our current knowledge of elements is FALSE?

A) We now know of more than 110 elements, both natural and man-made.
B) 81 stable elements have been found on Earth.
C) 10 radioactive elements are also found on Earth.
D) We have now produced over 50 radioactive elements not occurring in nature.
E) Technetium is found in giant stars, but not yet in nature on the Earth.

Question 67

After reaching its peak luminosity in hours or days,a nova declines in brightness over a period of a few ________ before returning to its pre-explosion luminosity.

Question 68

Why does neutron capture work?

A) Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei.
B) Neutrinos, because of their low mass and high speed, easily penetrate nuclei.
C) Single protons have little repulsion to heavy nuclei and easily fuse with them.
D) Photodisintegration makes many alpha particles, available for capture by nuclei.
E) Neutronization captures all the protons and electrons.

Question 69

An iron core will collapse in approximately one ________ in a type II supernova event.

Question 70

The maximum mass of a white dwarf is about ________ times the mass of the Sun.

Question 71

As a star evolves,heavier elements tend to form by various processes.Which of the following is NOT one of these processes?

A) proton capture and neutron capture
B) fusion of like nuclei
C) helium capture
D) the s process
E) neutronization

Question 72

As seen in 1987,when two silicon 28 nuclei fuse,or when seven alpha particles are added to a Si-28 nucleus,the initial result in either case is:

A) the shedding of bipolar planetary nebula shells.
B) a nova explosion.
C) iron 56.
D) cobalt 56.
E) nickel 56.

Question 73

The iron we commonly find in our surroundings came from:

A) the iron core of a massive star which exploded as a type I supernova.
B) planetary nebulae.
C) jets ejected by a rapidly spinning pulsar.
D) material ejected by a nova explosion.
E) decay of nickel 56 and cobalt 56 in a supernova remnant.

Question 74

What direct evidence do astronomers have that supports the heavy element formation in stars?

A) the presence of technetium in giant star spectra
B) observed elemental abundances
C) gamma-ray emissions from decay of cobalt 56 in supernovae
D) light curves of type-I supernovae
E) All of the above are evidence of this.

Question 75

What is the reason a type I supernova slows its dimming after about 2 months?

A) The planetary nebula cooled enough to form a dust shell.
B) Energy is released from the decay of radioactive cobalt 56 to iron 56.
C) The supernova remnant suddenly becomes transparent.
D) The burst of energy carried by neutrinos is finally observed.
E) Energy from the supernova's shock wave is released as it hits interstellar matter.

Question 76

Of all elements,________ has the most stable and tightly bound nucleus.

Question 77

When helium capture occurs with a carbon 12 nucleus,what results?

A) nitrogen 14
B) oxygen 16
C) neon 20
D) silicon 28
E) nickel 56

Question 78

In a nova,there is a white dwarf,an evolving companion star,and a(n)________ surrounding the white dwarf's equator.

Question 79

The making of abundant iron nuclei is typical of:

A) planetary nebula ejection.
B) the helium flash.
C) all novae.
D) type I supernovae.
E) type II supernovae.

Question 80

Type II supernovae and star forming regions are related to one another because:

A) they both contain ionized hydrogen.
B) they both involve high mass ionizing stars.
C) the shock waves of a supernova can trigger star formation.
D) as a result of both processes, lighter elements are transformed into heavier elements.
E) All of the above.