question

Why is the post-Main Sequence structure of a high mass star sometimes described by an "onion-layer" model? Explain. (SA)

answer

Late in the evolution of massive stars, fusion reactions create cores within cores within cores, etc. Hydrogen fusion occurs in a layer around a layer of helium fusion which occurs around of layer of carbon fusion... around oxygen fusion... around neon fusion... etc. The deeper you go, the heavier elements you find made, and the higher the temperature needed to sustain that particular fusion reaction.

question

The alpha process tends to produce chiefly

answer

even numbered elements.

question

The total energy emitted by the brightest nova explosions is about

answer

a million Suns.

question

What produces a type-I supernova?

answer

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

question

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

answer

nickel 56.

question

For a nova to occur, the system must have already been a

answer

mass-transfer binary.

question

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

answer

they immediately pass through the core and escape to space.

question

The making of abundant iron nuclei is typical of

answer

type II supernovae.

question

Which of these events is not possible?

answer

white dwarfs and companion stars producing recurrent Type I supernova events

question

Where was supernova 1987a located?

answer

in our companion galaxy, the Large Magellanic Cloud

question

Type I supernovae are NOT

answer

rich in hydrogen from the outer envelope of the collapsed star.

question

A star can be a supernova

answer

only once.

question

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

answer

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

question

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

answer

contain no ionizing stars.

question

An iron core cannot support a star because

answer

iron cannot fuse with other nuclei to produce energy.

question

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

answer

nova

question

In neutronization of the core, a proton and an electron make a neutron and a

answer

neutrino.

question

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

answer

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

question

The Chandrasekhar limit is

answer

the upper mass limit for a white dwarf.

question

What made supernova 1987a so useful to study?

answer

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

question

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

answer

ten billion

question

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

answer

a Type II supernova

question

A recurrent nova could eventually build up to a

answer

Type I supernova.

question

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

answer

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

question

Which statement about our current knowledge of elements is FALSE?

answer

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

question

What do X-ray observations tell us about conditions around a potential nova? (SA)

answer

The mass transfer causes an accretion disk to build up around the white dwarf, and as the material spirals in toward the strong gravity of the collapsed star, it is heated up to millions of degrees, hence becoming observable in X-rays. In some cases, this disk is so hot that it outshines the white dwarf, even in visible light. Fluctuations in the transfer create observable short period changes in its light.

question

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

answer

hydrogen and helium.

question

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?

answer

100 times more

question

Which statement about young stars is FALSE?

answer

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

question

The heaviest nuclei of all are formed

answer

in the core collapse that set the stage of Type II supernovae.

question

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

answer

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

question

What evidence is there that supernovae really have occurred?

answer

Crab Nebula observations of the actual explosions existence of heavy radioactive elements in nature supernova remnants all of the above

question

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

answer

day.

question

How does the death of one very massive star give birth to perhaps hundreds of smaller ones soon thereafter? (SA)

answer

The more massive the star, the faster it evolves, and less time it has to leave its stellar nursery and dense molecular cloud. When it explodes while still close to this dense region, its shock wave will trigger compression and collapse of many smaller protostars all at once.

question

Can our Sun ever become a nova? Why? (SA)

answer

No, ours is a single star, with no close companion to supply fresh hydrogen via mass transfer onto the surface of our collapsed white dwarf Sun billions of years from now.

question

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

answer

a type I supernova

question

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

answer

neutronization

question

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

answer

1054 AD by Chinese and other oriental and mid eastern astronomers.

question

For a white dwarf to explode entirely as a Type I supernova, it's mass must be

answer

1.4 solar masses, the Chandrasekhar Limit.

question

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

answer

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

question

The Chandrasekhar mass limit is

answer

1.4 solar masses.

question

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

answer

a. the shock waves of a supernova can trigger star formation. b. they both contain ionized hydrogen. c. as a result of both processes, lighter elements are transformed into heavier elements. d. they both involve high mass ionizing stars. ALL OF THE ABOVE

question

Which of these is NOT true about supernovae?

answer

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

question

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

answer

a. gamma-ray emissions from decay of cobalt 56 in supernovae b. the presence of technetium in giant star spectra c. observed elemental abundances d. light curves of type-I supernovae ALL OF THE ABOVE ARE EVIDENCE OF THIS

question

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

answer

oxygen 16

question

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

answer

neutrinos.

question

The iron we commonly find in our surroundings came from

answer

decay of nickel 56 and cobalt 56 in a supernova remnant.

question

Why does iron formation cause a high mass star to "have a heart attack"? (SA)

answer

Iron is the most tightly bonded of all nuclei. Fusion reactions leading to its production release radiation pressure to resist gravity, but all heavier nuclei beyond iron will absorb energy in their formation, so without the radiation to keep it inflated, the core collapses rapidly.

question

The iron we commonly find in our surroundings came from

answer

decay of nickel 56 and cobalt 56 in a supernova remnant.

question

What is stellar nucleosynthesis?

answer

The formation of heavier elements inside stars.

Astronomy Chapter 21 Quiz Q&As – Flashcards

Unlock all answers in this set

Haven't found what you were looking for?

Search for samples, answers to your questions and flashcards