Deck 14: Neutron Stars and Black Holes

Question 1

None of the pulsars emit visible light because

A) pulsars are too hot to emit visible light.
B) pulsars contain black holes that won't let visible light escape.
C) the gravitational field of a pulsar is so great that the visible light emitted is red shifted.
D) pulsars are too far away for the visible light to be bright enough to be detected at Earth.
E) The premise is false.A few pulsars are known to emit visible light pulses.

Answer 1

The premise is false.A few pulsars are known to emit visible light pulses.

Question 2

What is the escape velocity from the surface of a neutron star with a mass of 2 and a radius of 10 km?

A) 5.3*10¹⁶ m/sec
B) 1.6*10⁸ km/sec
C) 2.3*10⁸ m/sec
D) 2.3*10⁸ km/sec
E) 3.0*10⁸ m/sec

Answer 2

2.3*10⁸ m/sec

Question 3

Cygnus X-1 and LMC X-3 are black holes if the masses of the unseen companions are

A) less than 5 solar masses.
B) more than 5 solar masses.
C) between 0.4 and 1.4 solar masses.
D) less than 0.4 solar masses.
E) not larger than the masses of the stars that we can see.

Answer 3

more than 5 solar masses.

Question 4

A rotating black hole

A) will produce a pulsar.
B) will have a stronger gravitational field than a non-rotating black hole.
C) is known as a Schwarzschild black hole.
D) causes objects near it to produce large amounts of radio energy.
E) possesses an ergosphere that lies just beyond the Schwarzschild radius.

Question 5

A neutron star is expected to spin rapidly because

A) they conserved angular momentum when they collapsed.
B) they have high orbital velocities.
C) they have high densities.
D) they have high temperatures.
E) the energy from the supernova explosion that formed them made them spin faster.

Question 6

The search for black holes involves

A) searching for single stars that emit large amounts of x-rays.
B) finding x-ray binaries where the compact companion has a mass in excess of 3.
C) searching for large spherical regions from which no light is detected.
D) looking for pulsars with periods less than one millisecond.

Question 7

At extremely high densities and temperatures,electrons can be forced to fuse with protons.This reaction produces

A) hydrogen.
B) Helium and energy.
C) degenerate electrons.
D) neutrons and neutrinos.
E) large amounts of radio radiation.

Question 8

The density of a neutron star is

A) about the same as that of a white dwarf.
B) about the same as that of the sun.
C) about the same as an atomic nucleus.
D) about the same as a water molecule.
E) smaller than expected because the magnetic field is so strong.

Question 9

A pulsar requires that a neutron star

A) I & III
B) I & IV
C) II,III,& IV
D) I,III,& IV
E) I,II,III,& IV

Question 10

Although neutron stars are very hot,they are not easy to locate because

A) light does not escape from their event horizon.
B) most lie beyond dense dust clouds.
C) solid neutron material cannot radiate photons.
D) they are only found in other galaxies.
E) they have small surface areas.

Question 11

The event horizon

A) is believed to be a singularity.
B) is a crystalline layer.
C) has a radius equal to the Schwarzschild radius.
D) marks the inner boundary of a planetary nebula.
E) is located at the point where synchrotron radiation is created around a pulsar.

Question 12

The peculiar system SS 433

A) I
B) III
C) II & III
D) I,II,& III
E) I,II,III,& IV

Question 13

The Schwarzschild radius of a 2 black hole is approximately

A) 6 km.
B) 4 km.
C) 2 km.
D) 12 km.
E) 36 km.

Question 14

An isolated black hole in space would be difficult to detect because

A) there would be no light source nearby.
B) it would not be rotating rapidly.
C) it would be stationary.
D) very little matter would be falling into it.
E) there would be very few stars behind it whose light the black hole could block out.

Question 15

Which of the following objects is considered to possibly contain a black hole?

A) the central star of the Crab nebula
B) the Orion nebula
C) LMC X-3
D) Algol
E) PSR 1257+12

Question 16

The orbit of the binary pulsar,PSR 1936+16,studied by Taylor and Hulse

A) is so small that the orbital period is smaller than the pulsar period.
B) is growing smaller,presumably by emitting gravitational waves.
C) provides evidence that it is being orbited by at least 6 planets the size of Jupiter.
D) shows large changes each time an x-ray burst is emitted from the system.
E) contains a white dwarf and a black hole.

Question 17

The escape velocity of an object depends on

A) I,II,III,IV,& V
B) I & IV
C) I,II,III,& V
D) I,III,& V
E) I & III

Question 18

Millisecond pulsars that are very old are

A) believed to be the result of mass transfer from a companion that increases the mass of the pulsar.
B) all single objects.
C) not spinning as rapidly as they seem because they have four hot spots that produce the flashes.
D) x-ray binaries.
E) gamma-ray bursters.

Question 19

Glitches are associated with

A) x-ray bursters.
B) rapidly rotating black holes.
C) the collapse of a white dwarf to form a neutron star.
D) changes in the rotation rate of a pulsar.
E) planets that orbit pulsars.

Question 20

The density of a ____ is greater than the density of a ____.

A) white dwarf,neutron star
B) neutron star,black hole
C) pulsar,neutron star
D) pulsar,white dwarf
E) white dwarf,black hole

Question 21

The material that accretes onto a neutron star or black hole is expected to emit x-rays because

A) the material will produce synchrotron radiation because of the strong magnetic field.
B) hydrogen nuclei begin to fuse and emit high energy photons.
C) the material will become hot enough that it will radiate most strongly at x-ray wavelengths.
D) as the material slows down it converts thermal energy to gravitational potential energy.
E) none of the above

Question 22

Pulsars could not be pulsating stars because the pulses are too short.

Question 23

The singularity of a black hole

A) is found on the surface of the event horizon.
B) is located at the center of the event horizon.
C) can only be located if the black hole is in a binary system.
D) doesn't exist since all black holes have a finite size.

Question 24

If the accretion disk around a black hole emits x-rays outside the event horizon,then the x-rays can escape.

Question 25

Neutron stars have densities roughly the same as that of the atomic nucleus.

Question 26

Unseen objects in our galaxy have been found by the bending effect they have on more distant stars' light passing near them.These small objects that don't emit light are calculated to have masses of about 10x the mass of the sun.Which is the best choice for these objects?

A) black hole
B) neutron star
C) white dwarf
D) main sequence stars

Question 27

The escape velocity at the event horizon around a black hole is

A) smaller than the speed of light.
B) equal to the speed of light.
C) larger than the speed of light.
D) irrelevant since nothing (including light)can escape from a black hole.

Question 28

Neutron stars were first discovered in the 1930s.

Question 29

Theory predicts that neutron stars may not exceed 3 solar masses.

Question 30

The figure shows an image of an isolated black hole.A black hole emits...

A) light with wavelengths in the black color region.
B) no light from inside the event horizon.
C) light which is blueshifted to shorter wavelenghs as it escapes.
D) light which is redshifted to shorter wavelengths as it escapes.

Question 31

A black hole can be thought of as

A) a very massive object of finite size.
B) a shell of material expanding from a white dwarf.
C) a massive body of infinitely small size.
D) a burnt out white dwarf.

Question 32

As material flows into a black hole

A) the material will experience time dilation.
B) the material will become hotter.
C) the material will produce an absorption spectrum.
D) the material will increase in mass.
E) a and b

Question 33

To determine whether the compact object in an x-ray binary is a neutron star or a black hole,we must find the temperature of the compact object.

Question 34

How far does the Schwarzschild radius of the Sun extend from its center?

A) A few kilometers away
B) A few solar radii away
C) A few astronomical units (AU)away
D) A few parsecs away

Question 35

The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus.

Question 36

The object left behind after the 1054 AD supernova explosion has been observed at the center of the Crab nebula.The object is a ...

A) white dwarf
B) neutron star
C) red giant
D) proto-star

Question 37

Which of the kinds of stars below would you expect to find in a 11 billion year old globular cluster of stars?

A) cool,low luminosity main sequence stars
B) white dwarfs
C) neutron stars
D) red giants
E) all of the above

Question 38

Many pulsars have periods that are gradually increasing as the spinning neutron stars lose energy.

Question 39

We expect neutron stars to spin rapidly because they conserve angular momentum.

Question 40

Which of the following can you never know about a black hole?

A) Mass
B) Rotation
C) Electrical charge
D) The material that has fallen in.

Question 41

A(n)____________________ periodically emits large amounts of x-ray radiation as material accretes around a neutron star or black hole.

Question 42

The ____________________ of a black hole in a binary system can emit X-rays and allow us to detect the presence of the black hole.

Question 43

A(n)____________________ is a rapidly spinning neutron star that accelerates charged particles near the poles of its magnetic field.

Question 44

LMC X-3 is a binary system that is believed to contain a black hole.

Question 45

Rotating black holes are called Kerr black holes.

Question 46

Material within the ____________________ of a rotating black hole is forced to orbit the black hole due to the curvature of space time,but it could still escape the gravitational pull of the black hole.

Question 47

A rotating black hole is referred to as a(n)____________________ black hole.

Question 48

When a star,of mass comparable to the Sun,dies it become a black hole.