Question 1

Why does the size of a white dwarf decrease with increasing mass?

Accepted Answer

A more massive white dwarf has a stronger gravitational force that compresses its mass to a greater density. The degeneracy pressure that supports a white dwarf against collapse increases as the density increases, and the balance between degeneracy pressure and gravity is reached such that the a more massive white dwarf is smaller in radius.
Answer Key Testname: C14

Question 2

Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure.

Accepted Answer

A) True 
 B)False  True

Question 3

No visible light can escape a black hole, but things such as gamma rays, X- rays, and neutrinos can.

Accepted Answer

A) True 
 B)False  False

Question 4

Which of the following best describes what would happen if a 1.5 solar mass neutron star, with a diameter of a few kilometers, were suddenly to appear in your hometown?

Accepted Answer

A) It would rapidly sink to the center of the Earth. 
B) The entire mass of the Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star. 
C) The combined mass of the Earth and the neutron star would cause the neutron star to collapse into a black hole. 
D) It would crash into the Earth, throwing vast amounts of dust into the atmosphere which in turn would cool the Earth. Such a scenario is probably what caused the extinction of the dinosaurs. 
E) It would crash through the Earth, creating a large crater, and exit the Earth on the other side. 
A) It would rapidly sink to the center of the Earth. 
B) The entire mass of the Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star. 
C) The combined mass of the Earth and the neutron star would cause the neutron star to collapse into a black hole. 
D) It would crash into the Earth, throwing vast amounts of dust into the atmosphere which in turn would cool the Earth. Such a scenario is probably what caused the extinction of the dinosaurs. 
E) It would crash through the Earth, creating a large crater, and exit the Earth on the other side.

Question 5

A typical white dwarf is .

Accepted Answer

A) as massive as the Sun but only about as large in size as Earth 
B) as massive as the Sun but only about as large in size as Jupiter 
C) about the same size and mass as the Sun but much hotter 
D) as large in diameter as the Sun but only about as massive as Earth 
A) as massive as the Sun but only about as large in size as Earth 
B) as massive as the Sun but only about as large in size as Jupiter 
C) about the same size and mass as the Sun but much hotter 
D) as large in diameter as the Sun but only about as massive as Earth

Question 6

Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?

Accepted Answer

A) Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted. 
B) Time on the clock will run faster as it approaches the black hole, and light from the clock will be increasingly blueshifted. 
C) The clock will fall faster and faster, reaching the speed of light as it crosses the event horizon. 
D) The clock will fall toward the black hole at a steady rate, so that you'll see it plunge through the event horizon within just a few minutes. 
A) Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted. 
B) Time on the clock will run faster as it approaches the black hole, and light from the clock will be increasingly blueshifted. 
C) The clock will fall faster and faster, reaching the speed of light as it crosses the event horizon. 
D) The clock will fall toward the black hole at a steady rate, so that you'll see it plunge through the event horizon within just a few minutes.

Question 7

A teaspoonful of white dwarf material on Earth would weigh

Accepted Answer

A) about the same as the Earth. 
B) about the same as Mt. Everest. 
C) a few grams. 
D) a few pounds. 
E) a few tons. 
A) about the same as the Earth. 
B) about the same as Mt. Everest. 
C) a few grams. 
D) a few pounds. 
E) a few tons.

Question 8

This figure shows how the luminosity of supernovae change over time. How long does it take a white dwarf supernova to decrease in luminosity by a factor of 100 from its peak?

Accepted Answer

A) about 200 days 
B) about 100 days 
C) about 300 days 
D) about 25 days 
A) about 200 days 
B) about 100 days 
C) about 300 days 
D) about 25 days

Question 9

The coolest white- dwarf: Surveys have been carried out to identify isolated white- dwarfs throughout the galaxy and its globular clusters. They have been found to span a range of temperatures, with a sharp lower limit of about 3000 K (i.e. many have been found at all temperatures from 10s of thousands of Kelvin down to 3000K, but none cooler). What does this observation reveal about the age of our galaxy?

Accepted Answer

The galaxy has a finite age, when enough

Question 10

Neutron stars are the densest objects that we can directly observe in the universe.

Accepted Answer

A) True 
 B)False

Question 11

A paperclip with the density of a neutron star would weigh (on the Earth)

Accepted Answer

A) a few tons. 
B) about the same as a regular paperclip. 
C) more than the Moon. 
D) more than the Earth. 
E) more than Mt. Everest. 
A) a few tons. 
B) about the same as a regular paperclip. 
C) more than the Moon. 
D) more than the Earth. 
E) more than Mt. Everest.

Question 12

What causes the radio pulses of a pulsar?

Accepted Answer

A) A black hole near the neutron star absorbs energy and re- emits it as radio waves. 
B) The neutron star undergoes periodic explosions of nuclear fusion that generate radio pulses. 
C) As the neutron star spins, beams of radio radiation sweep through space. If one of the beams crosses the Earth, we observe a pulse. 
D) The neutron star's orbiting companion periodically eclipses the radio waves that the neutron star emits. 
E) The vibration of the neutron star 
A) A black hole near the neutron star absorbs energy and re- emits it as radio waves. 
B) The neutron star undergoes periodic explosions of nuclear fusion that generate radio pulses. 
C) As the neutron star spins, beams of radio radiation sweep through space. If one of the beams crosses the Earth, we observe a pulse. 
D) The neutron star's orbiting companion periodically eclipses the radio waves that the neutron star emits. 
E) The vibration of the neutron star

Question 13

A white dwarf is .

Accepted Answer

A) an early stage of a neutron star 
B) a brown dwarf that has exhausted its fuel for nuclear fusion 
C) a precursor to a black hole 
D) what most stars become when they die 
A) an early stage of a neutron star 
B) a brown dwarf that has exhausted its fuel for nuclear fusion 
C) a precursor to a black hole 
D) what most stars become when they die

Question 14

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

Accepted Answer

A) Electron degeneracy pressure is the main source of pressure in white dwarfs, while neutron degeneracy pressure is the main source of pressure in neutron stars. 
B) In a black hole, the pressure coming from neutron degeneracy pressure is slightly greater than that coming from electron degeneracy pressure. 
C) Both electron degeneracy pressure and neutron degeneracy pressure help govern the internal structure of a main- sequence star. 
D) The life of a white dwarf is an ongoing battle between electron degeneracy pressure and neutron degeneracy pressure. 
A) Electron degeneracy pressure is the main source of pressure in white dwarfs, while neutron degeneracy pressure is the main source of pressure in neutron stars. 
B) In a black hole, the pressure coming from neutron degeneracy pressure is slightly greater than that coming from electron degeneracy pressure. 
C) Both electron degeneracy pressure and neutron degeneracy pressure help govern the internal structure of a main- sequence star. 
D) The life of a white dwarf is an ongoing battle between electron degeneracy pressure and neutron degeneracy pressure.

Question 15

The maximum mass for a white dwarf is 1.4 solar masses.

Accepted Answer

A) True 
 B)False

Question 16

What kind of pressure supports a white dwarf?

Accepted Answer

A) thermal pressure 
B) neutron degeneracy pressure 
C) radiation pressure 
D) electron degeneracy pressure 
E) all of the above 
A) thermal pressure 
B) neutron degeneracy pressure 
C) radiation pressure 
D) electron degeneracy pressure 
E) all of the above

Question 17

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

Accepted Answer

A) It emits most strongly in visible and ultraviolet light. 
B) Every decade or so, it erupts in a nova explosion. 
C) It is surrounded by a planetary nebula. 
D) It dims and brightens more than twice per second. 
A) It emits most strongly in visible and ultraviolet light. 
B) Every decade or so, it erupts in a nova explosion. 
C) It is surrounded by a planetary nebula. 
D) It dims and brightens more than twice per second.

Question 18

In which wavelength region(s)would we need to carry out observations in order to study the accretion disk around a white dwarf in a binary system?

Accepted Answer

A) visible light 
B) ultraviolet light 
C) X- ray light 
D) A and B 
E) B and C 
A) visible light 
B) ultraviolet light 
C) X- ray light 
D) A and B 
E) B and C

Question 19

Which of the following observatories is most likely to discover a black hole in a binary system?

Accepted Answer

A) the Arecibo Radio Observatory 
B) the Hubble Space Telescope 
C) the SOFIA airborne infrared observatory 
D) the Chandra X- Ray Observatory 
A) the Arecibo Radio Observatory 
B) the Hubble Space Telescope 
C) the SOFIA airborne infrared observatory 
D) the Chandra X- Ray Observatory

Question 20

There is no upper limit to the mass of a neutron star.

Accepted Answer

A) True 
 B)False

Why does the size of a white dwarf decrease with increasing mass?

Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure.

No visible light can escape a black hole, but things such as gamma rays, X- rays, and neutrinos can.

Which of the following best describes what would happen if a 1.5 solar mass neutron star, with a diameter of a few kilometers, were suddenly to appear in your hometown?

A typical white dwarf is .

Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?

A teaspoonful of white dwarf material on Earth would weigh

This figure shows how the luminosity of supernovae change over time. How long does it take a white dwarf supernova to decrease in luminosity by a factor of 100 from its peak?

Neutron stars are the densest objects that we can directly observe in the universe.

A paperclip with the density of a neutron star would weigh (on the Earth)

What causes the radio pulses of a pulsar?

A white dwarf is .

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

The maximum mass for a white dwarf is 1.4 solar masses.

What kind of pressure supports a white dwarf?

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

In which wavelength region(s)would we need to carry out observations in order to study the accretion disk around a white dwarf in a binary system?

Which of the following observatories is most likely to discover a black hole in a binary system?

There is no upper limit to the mass of a neutron star.

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

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Exam 14: The Bizarre Stellar Graveyard

Why does the size of a white dwarf decrease with increasing mass?

Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure.

No visible light can escape a black hole, but things such as gamma rays, X- rays, and neutrinos can.

Which of the following best describes what would happen if a 1.5 solar mass neutron star, with a diameter of a few kilometers, were suddenly to appear in your hometown?

A typical white dwarf is .

Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?

A teaspoonful of white dwarf material on Earth would weigh

This figure shows how the luminosity of supernovae change over time. How long does it take a white dwarf supernova to decrease in luminosity by a factor of 100 from its peak?

Neutron stars are the densest objects that we can directly observe in the universe.

A paperclip with the density of a neutron star would weigh (on the Earth)

What causes the radio pulses of a pulsar?

A white dwarf is .

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

The maximum mass for a white dwarf is 1.4 solar masses.

What kind of pressure supports a white dwarf?

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

In which wavelength region(s)would we need to carry out observations in order to study the accretion disk around a white dwarf in a binary system?

Which of the following observatories is most likely to discover a black hole in a binary system?

There is no upper limit to the mass of a neutron star.

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Filters