Astronomy Ch. 21 TEST: Stellar Explosions

Under what circumstances will a nova occur? Can our Sun ever become a nova? Why?

A nova occurs when the white dwarf "steals" gas from its nearby companion star. When enough gas builds up on the surface of the white dwarf it triggers an explosion. As long as it continues to take gas from its companion star, the white dwarf can produce nova outbursts at regular intervals. No because it's too small and there isn't enough mass

The Chandrasekhar mass limit is a. 1.4 solar masses. b. .08 solar masses. c. .4 solar masses. d. 8 solar masses. e. 3 solar masses.

a: 1.4 solar masses

Which statement about young stars is FALSE? a. Being young, they will have more pure hydrogen than earlier generations. b. They are more likely to have planets forming with them than earlier generations. c. The high mass stars will be more likely to produce heavier elements as they evolve. d. They are born in a dustier environment than earlier generations. e. They contain a larger fraction of heavy elements than previous generations.

a: Being young, they will have more pure hydrogen than earlier generations

The heaviest nuclei of all are formed a. by neutron capture during a type II supernova explosion. b. during carbon burning in the giant stage. c. during the triple alpha process. d. during a carbon detonation supernova. e. during a nova explosion.

a: by neutron capture during a type II supernova explosion

The heaviest nuclei of all are formed a. in the core collapse that set the stage of Type II supernovae. b. during nova explosions. c. in the horizontal branch. d. in dense white dwarfs. e. in the ejection of matter in the planetary nebula.

a: in the core collapse that set the stage of a Type II supernova.

In order of visual luminosity at the start, which is most luminous? a. a nova b. a Type I supernova c. a planetary nebula d. a red supergiant e. a Type II supernova

b: A Type I supernova

What is the reason a Type-I supernova slows its dimming after about 2 months? a. The supernova remnant suddenly becomes transparent. b. Energy is released from the decay of radioactive cobalt 56 to iron 56. c. Energy from the supernova's shock wave is released as it hits interstellar matter. d. The planetary nebula cooled enough to form a dust shell. e. The burst of energy carried by neutrinos is finally observed.

b: Energy is released from the decay of radioactive cobalt 56 to iron 56

Which of these is NOT true about supernovae? a. Type II involves formation of iron in the core. b. The two types are both closely related to evolution of white dwarfs. c. The one in 1987 in the Large Magellanic Cloud was of type II. d. Type I involves carbon detonation. e. Neutronization is vital in understanding type II core collapse.

b: The two types are both closely related to evolution of white dwarfs

The total energy emitted by the brightest nova explosions is about a. 50,000 of our Sun. b. a million of our Sun. c. a billion of our Sun. d. 1,000 of our Sun. e. a trillion of our Sun.

b: a million of our Sun.

What produces a type-I supernova? a. a nova igniting a helium flash in its red giant companion b. mass transfer onto a white dwarf pushing it over 1.4 solar masses c. the radioactive decay of nickel 56 into cobalt 56 into iron 56 d. the collapse of the core of a massive star e. the helium flash blows apart a giant's core

b: mass transfer onto a white dwarf pushing it over 1.4 solar masses

For a white dwarf to explode entirely as a Type I supernova, it's mass must be a. 3 solar masses, the Schwartzschild Limit. b. at least 0.08 solar masses. c. 1.4 solar masses, the Chandrasekhar Limit. d. 100 solar masses, the most massive known stars. e. 20 solar masses, the Hubble Limit.

c: 1.4 solar masses, the Chandrasekhar Limit

What can you conclude about a Type I supernova? a. Its core was mostly iron. b. It was originally a high mass star. c. It was originally a low-mass star. d. Its spectrum will show large amounts of hydrogen. e. The star never reached the Chandrasekhar Limit.

c: It was originally a low-mass star.

A recurrent nova could eventually build up to a a. Type II supernova. b. quasar. c. Type I supernova. d. planetary nebula. e. hypernova.

c: Type I supernova

Which of these does not depend on a close binary system to occur? a. a Type I supernova b. a nova c. a Type II supernova d. all of these need mass transfer to occur. e. None of these depend on mass transfer.

c: a Type II supernova

Which of these is the likely progenitor of a Type I supernova? a. an evolved red giant which is just starting to make silicon in its core b. a contact binary, with the neutron star at 2.3 solar masses c. a mass-transfer binary, with the white dwarf already at 1.3 solar masses d. an evolved blue supergiant that is about to experience the helium flash e. a helium-neon white dwarf

c: a mass-transfer binary, with the white dwarf already at 1.3 solar masses

The alpha process tends to produce chiefly a. only radioactive elements. b. stable elements. c. even numbered elements. d. only carbon. e. odd numbered elements.

c: even numbered elements

As a star evolves, heavier elements tend to form by various processes. Which of the following is not one of these processes? a. helium capture b. fusion of like nuclei c. neutronization d. proton capture and neutron capture e. the s process

c: neutronization

At temperatures of ________ K, photons can split apart nuclei until only protons and neutrons are left in photodisintegration. a. one billion b. one hundred billion c. ten billion d. 100 million e. ten million

c: ten billion

When a stellar iron core collapses, large numbers of neutrinos are formed, then: a. they are captured to form light elements. b. they form the neutron star. c. they immediately pass through the core and escape to space. d. they are captured to form heavy elements. e. they are absorbed by electrons to produce positrons.

c: they immediately pass through the core and escape to space.

The supernova that formed M-1, the Crab Nebula, was observed in a. 1006 by observers in the southern hemisphere. b. about 9,000 BC by all our ancestors. c. 1572 AD by Tycho Brahe. d. 1054 AD by Chinese and other oriental and mid eastern astronomers. e. 1604 AD by Johannes Kepler.

d: 1054 AD by Chinese and other oriental and mid eastern astronomers

Why does neutron capture work? a. Single protons have little repulsion to heavy nuclei and easily fuse with them. b. Neutronization captures all the protons and electrons. c. Neutrinos, because of their low mass and high speed, easily penetrate nuclei. d. Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei. e. Photodisintegration makes many alpha particles, available for capture by nuclei.

d: Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei

If it gains sufficient mass, a white dwarf can become a a. black dwarf. b. planetary nebula. c. brown dwarf. d. Type I supernova. e. Type II supernova.

d: Type I supernova

The making of abundant iron nuclei is typical of a. all novae. b. planetary nebula ejection. c. the helium flash. d. type II supernovae. e. type I supernovae.

d: Type II supernova

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. month. b. week. c. century. d. day. e. year.

d: a day

The iron we commonly find in our surroundings came from a. planetary nebulae. b. material ejected by a nova explosion. c. the iron core of a massive star which exploded as a type I supernova. d. decay of nickel 56 and cobalt 56 in a supernova remnant. e. jets ejected by a rapidly spinning pulsar.

d: decay of nickel 56 and cobalt 56 in a supernova remnant

An iron core cannot support a star because a. iron supplies too much pressure. b. iron is in the form of a gas, not a solid, in the center of a star. c. iron has poor nuclear binding energy. d. iron cannot fuse with other nuclei to produce energy. e. iron is the heaviest element, and sinks upon differentiation.

d: iron cannot fuse with other nuclei to produce energy.

In neutronization of the core, a proton and an electron make a neutron and a a. pion. b. positron. c. muon. d. neutrino. e. antineutron.

d: neutrino

Most of the energy of the supernova is carried outward via a flood of a. positrons. b. helium nuclei. c. gamma rays. d. neutrinos. e. protons.

d: neutrinos

A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object? a. type I supernova b. type II supernova c. hypernova d. nova e. gamma ray burstar

d: nova

A star can be a supernova a. only if it can fuse iron in its core. b. a few times, at unpredictable intervals. c. in predictable cycles of decades. d. only once. e. before it reaches the main sequence, if it is massive enough.

d: only once

Which of these events is not possible? a. a white dwarf being found in the center of a planetary nebula b. close binary stars producing recurrent novae explosions c. red giants exploding as Type II supernovae d. white dwarfs and companion stars producing recurrent Type I supernova events e. low-mass stars swelling up to produce planetary nebulae

d: white dwarfs and companion stars producing recurrent Type I supernova events

What evidence is there that supernovae really have occurred? a. supernova remnants b. Crab Nebula c. observations of the actual explosions d. existence of heavy radioactive elements in nature e. all of the above

e LOOK UP ANSWER

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. ten times more b. about twice as much c. about equal amounts d. only .007 as much e. 100 times more

e: 100 times more

What made supernova 1987a so useful to study? a. In the Large Magellanic Cloud, we already knew its distance. b. It occurred after new telescopes, such as Hubble, could observe it very closely. c. Its progenitor had been observed previously. d. We saw direct evidence of nickel to iron decay in its light curve. e. All of the above are correct.

e: All of the above are correct

What direct evidence do astronomers have that supports the heavy element formation in stars? a. gamma-ray emissions from decay of cobalt 56 in supernovae b. light curves of type-I supernovae c. observed elemental abundances d. the presence of technetium in giant star spectra e. All of the above are evidence of this.

e: All of the above are evidence of this

Which type of heavy atomic nuclei are most common, and why? a. Noble gases, for they are the most stable elements. b. Metals, for iron is the last abundant element formed before the type II supernova. c. Odd numbered elements, because hydrogen is the building block for all heavier elements. d. Transuranium elements, for only very heavy elements are made in supernovae. e. Even numbered elements, for helium is "giant food" for everything beyond itself.

e: Even numbered elements, for helium is "giant food" for everything beyond itself

What is stellar nucleosynthesis? a. The formation of planetary nebulae by red giants. b. The process by which stars form interstellar dust. 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 formation of heavier elements inside stars.

e: The formation of heavier elements inside stars

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. Technetium is found in giant stars, but not yet in nature on the Earth. c. 81 stable elements have been found on Earth. d. 10 radioactive elements are also found on Earth. e. We have now produced over 50 radioactive elements not occurring in nature.

e: We have now produced over 50 radioactive elements not occurring in nature.

Type II supernovae and star forming regions are related to one another because a. the shock waves of a supernova can trigger star formation. b. they both involve high mass ionizing stars. c. as a result of both processes, lighter elements are transformed into heavier elements. d. they both contain ionized hydrogen. e. all of the above

e: all of the above

As a star's evolution approaches the Type II supernova, we find a. photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova. b. the heavier the element, the less time it takes to make it. c. the heavier the element, the higher the temperature to fuse it. d. helium to carbon fusion takes at least 100 million K to start. e. All of the above are correct.

e: all of the above are correct

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. an evolved blue supergiant that is about to experience the helium flash c. two white dwarfs in a contact binary system d. a contact binary, with the neutron star at 2.3 solar masses e. an evolved red giant which is just starting to make silicon in its core

e: an evolved red giant which is just starting to make silicon in its core

Supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants a. are more diffuse than star forming regions. b. don't look like star forming regions. c. are much bigger than star forming regions. d. are located far from star forming regions. e. contain no ionizing stars.

e: contain no ionizing stars

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. gravity. d. the dark force. e. fission of heavy nuclei back toward lighter ones.

e: fission of heavy nuclei back toward lighter ones

Nearly all the elements found in nature were formed inside stars, except for a. uranium and radium. b. carbon and silicon. c. silver and technetium. d. helium and carbon. e. hydrogen and helium.

e: hydrogen and helium.

Where was supernova 1987a located? a. in M-13, one of the closest of the evolved globular clusters b. near the core of M-31, the Andromeda Galaxy c. in Sagittarius, near the Galactic Nucleus d. in the Orion Nebula, M-42 e. in our companion galaxy, the Large Magellanic Cloud

e: in our companion galaxy, the Large Magellanic Cloud

For a nova to occur, the system must have already been a a. spectroscopic binary. b. astrometric binary. c. eclipsing binary. d. detached binary. e. mass-transfer binary.

e: mass-transfer binary

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. cobalt 56. d. iron 56. e. nickel 56.

e: nickel 56

When helium capture occurs with a carbon 12 nucleus, what results? a. nitrogen 14 b. nickel 56 c. neon 20 d. silicon 28 e. oxygen 16

e: oxygen 16

Type I supernovae are NOT a. created by carbon detonation. b. created by the mass of the white dwarf exceeding Chandrasekhar's Limit. c. products of mass transfer. d. brighter than type II supernovae. e. rich in hydrogen from the outer envelope of the collapsed star.

e: rich in hydrogen from the outer envelope of the collapsed star

The Chandrasekhar Limit is a. the point at which a planetary nebula forms. b. the temperature at which helium fusion starts. c. the lower mass limit for a Type II supernova. d. the temperature at which hydrogen fusion starts. e. the upper mass limit for a white dwarf.

e: the upper mass limit for a white dwarf