Chapter 13

How does doubling a star's core temperature affect its rate of nuclear fusion? a. It lowers it. b. It does not change it. c. It doubles it. d. It raises it by at least an order of magnitude. e. There's not enough information to answer the question.

Just after a star has exhausted the hydrogen in its core, the core properties differ from the those of the shell directly above it. Which of the following statements regarding the differences between the two layers is not true? a. The elemental composition differs. b. The density drops between the two layers. c. There is more gravitational pressure on the core. d. The hydrogen fraction is lower in the core. e. Nuclear fusion occurs in both the core and the shell.

As the hydrogen in the core of a star runs out, which of the following does not start to occur? a. Hydrogen burns in the shell above the core. b. Helium immediately burns in the core. c. The star's total energy output increases. d. The core contracts. e. The shell heats up.

A star is on the horizontal branch of the HR diagram. Which of the following describes nuclear fusion within the star? a. only hydrogen to helium in the core b. helium to carbon in the core; none in shells above the core c. no fusion in the core; hydrogen to helium in the first shell d. helium to carbon in the core; hydrogen to helium in the first shell e. no fusion in the core; helium to carbon in the first shell; hydrogen to helium in the second shell

Which of the following accurately describes changes to a star when it first moves off the main sequence of the HR diagram? a. increased radius and increased surface temperature b. increased radius and decreased surface temperature c. shorter wavelength of peak radiation d. decreased luminosity e. absence of nuclear fusion

A nearby star is observed to currently be in a stage of burning helium into carbon in a shell above the core. What mass can the star be? a. only low-mass b. only intermediate-mass c. only high-mass d. either intermediate-mass or massive e. any size

True/False: If a gas cloud were discovered that was composed only of elements up to and including the atomic weight of carbon, you could conclude with certainty that it did not originate from a supernova explosion.

Which of the following is not a possible source of an accretion disk? a. the birth of a new star b. one star pulling material from a binary companion c. a larger star pulling a smaller binary companion apart d. a slowly spinning single main-sequence star e. All are possible.

What does the Heisenberg uncertainty principle imply about the behavior of an electron? a. The more confined it is, the greater will be the range of its velocity. b. When its velocity is greater, it requires more space. c. The greater the uncertainty in its position, the higher will be the range of its velocity. d. The electron can be squeezed out when matter becomes degenerate. e. The charge of the electron is reduced when it is confined.

Which of the following has the highest density? a. intermediate-mass main-sequence star b. white dwarf c. neutron star d. planetary nebula e. high-mass main-sequence star

Which of the following statements about white dwarfs is true? a. They can be the remains of massive stars. b. They don't allow any light to escape. c. They first appear at the center of a planetary nebula. d. They are smaller than neutron stars. e. The larger their mass, the larger their radius.

The Chandrasekhar limit refers to a. the minimum mass of a very-low-mass main-sequence star. b. the minimum mass of a white dwarf or neutron star. c. the maximum mass of a white dwarf. d. the maximum mass of a neutron star. e. the maximum mass of a black hole.

A star is currently creating the element silicon. Which statement about it is true? a. It must be a low-mass star. b. It must be an intermediate-mass star on the main sequence. c. It must be an intermediate-mass star on the giant branch. d. It must be a high-mass star on the main sequence. e. It must be a high-mass star on the giant branch.

Which of the following statements about the sequential nuclear fusion that occurs in a high-mass star is true? a. The duration of fusion increases as increasingly heavy elements are produced. b. Lighter end products are created in each successive stage. c. The last element that serves as input to nuclear fusion is iron. d. Higher temperatures are required for nuclear fusion of each successively heavier element. e. Fusion can occur in only one shell at a time.

What characteristic do the processes that produce planetary nebulas and Type II supernovas share? a. electron degeneracy pressure b. density of the remaining star c. shape of the outflows d. mass of the dying star e. the outer layers of the star being driven into space

Which of the following is/are not characteristics that Type Ia and Type II supernovas have in common? Choose all that apply. a. mass of the dying star b. fusion of elements up through iron prior to the massive explosion c. creation of elements heavier than iron d. enormous shock waves e. usefulness as standard candles

Which statement accurately describes a neutron star? a. It is an object created from the outer layers of a high-mass star. b. It is a star fusing iron in its core. c. It is an object that results from the death of a massive star. d. It is an object created by electron degeneracy pressure. e. It is the end product of a very-low-mass star.

A pulsar is also a. a neutron star. b. a white dwarf. c. a strong source of visible light d. a dead low-mass star. e. the site of a nova.

Explain the relationship between mass and core temperature in stars and how it determines a star's longevity.

Describe how different elements are created and recycled by stellar life cycles.

What event signals the beginning of the death process for all stars?

Why does a midsized star move up and to the right on the HR diagram relative to the main sequence as it approaches death?

For low- and intermediate-mass stars like the Sun, what keeps the inner core from collapsing after the star's hydrogen fuel is depleted and fusion stops?

Subrahmanyan Chandrasekhar determined that the limit for a dead star to be supported by electron degeneracy pressure is \(1.4 M_{\mathrm{Sm}}\) What happens to stars more massive than that?

Explain why the stages of fusing progressively heavier elements move progressively more rapidly.

Why are massive stars unable to continue burning elements heavier than iron?

Explain why the stages of fusing progressively heavier elements move progressively more rapidly.

Describe the differences in the causes and observations of Type Ia and Type II supernovas. Which type serves as a standard candle?

A star's radius and temperature are both twice that of the Sun. How does its luminosity compare with the Sun's? Which had a greater effect on the final luminosity: the doubling of temperature or radius?

A star's temperature is 3 times as high as the Sun's, and its luminosity is 48 times that of the Sun. What is the ratio of the star's radius to the Sun's radius?

The temperature of a red giant is \(3,300 \mathrm{K},\) and its radius is 60 times that of the Sun. What is its luminosity, in \(L_{\mathrm{Sun}}\) ? Does this result make sense, given the cooler surface temperature of the red giant?

A red giant has a temperature of \(3,700 \mathrm{K}\) and luminosity of \(1.8 \times 10^{3} L_{\mathrm{Sun}} .\) What is its radius, in solar radii?

What is the wavelength of peak radiation, in meters, for a white dwarf with a temperature of \(35,000 \mathrm{K}\) ? What kind of light is this?

A neutron star has a temperature of \(50,000 \mathrm{K}\). What is the wavelength of its peak radiation, in meters? What kind of light is this?

What is the temperature, in kelvins, of a star with a peak wavelength of \(6.7 \times 10^{-7}\) meter?

A white dwarf has a peak radiation of \(3.3 \times 10^{-8}\) meter. What is its temperature, in kelvins?

A planetary nebula with a radius of \(0.1 \mathrm{pc}\) was created during the death of its star 3490 years ago. At what rate has it been expanding, in kilometers per second?