Monday, March 4, 2013

Study Guide Ch11


Chapter 11 Neutron Stars and Black Holes

Answer is slashed threw its not the right one if in red it might be the answer.
Question 1
Observations from the Compton Gamma Ray Observatory showed that gamma-ray bursters were located throughout the sky. This told us that
all of the above

Question 2
None of the pulsars emit pulses of visible light because
pulsars are to hot to emit visible light.
pulsars contain black holes that won't let visible light escape.
the gravitational field of a pulsar is so great that the visible light emitted is red shifted.
pulsars are too far away for the visible light to be bright enough to be detected at Earth.
A few pulsars do emit visible light pulses.

Question 3
The ____ of a black hole is the radius from a black hole at which the escape velocity is approximately equal to the speed of light.
event horizon

Question 4
 Which of the following can you never know about a black hole?
the elements of the material that has fallen in

Question 5
The density of a ____ is greater than the density of a ____.
pulsar, white dwarf

Question 6
Although neutron stars are very hot, they are faint and not easy to see at visual wavelengths because
both c and d {they have only a small surface area from which to emit./the peak of their thermal emission is at much shorter wavelengths than visual.}

Question 7
Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?
a and c {Science requires that experimental and theoretical findings be reproducible./
Scientific results are reviewed by other scientists before they are published.}

Question 8
Pulsars cannot be spinning white dwarfs because
a white dwarf spinning that fast would fly apart.

Question 9
A neutron star is expected to spin rapidly because
they conserved angular momentum when they collapsed.

Question 10
The slowing of clocks in strongly curved space time is known as
gravitational radiation.
time dilation.
gravitational curvature.
gravitational red shift.
hyperspace drag.

Question 11
Similar to the sun, pulsars’ rotations are believed to slow down because
they are losing angular momentum into space via outward streaming particles.

Question 12
As material flows into a black hole
the material will experience time dilation.
the material will become hotter.
the material will produce an absorption spectrum.
the material will appear to us to fall into the black hole very rapidly.
a and b

Question 13
The material that accretes onto a neutron star or black hole is expected to emit X-rays because
the material will become hot enough that it will radiate most strongly at X-ray wavelengths.

Question 14
The escape velocity of an object depends on
I. the mass of that object.
II. the mass of the object trying to escape.
III. the distance from the center of the object and the escaping object.
IV. the speed of light.
I & III

Question 15
The singularity of a black hole
is located within the event horizon.

Question 16
The size of a neutron star is
smaller than any of these.

Question 17
Millisecond pulsars that are very old are
believed to be the result of mass transfer from a companion that increases the spin of the pulsar.

Question 18
A pulsar requires that a neutron star
I. rotate rapidly.
II. have a radius of at least 10 km.
III. have a strong magnetic field.
IV. rotate on an axis that is different from the axis of the magnetic field.
I, III & IV

Question 19
____ occurs when light travels out of a gravitational field, loses energy, and its wavelength grows longer.
A gravitational redshift

Question 20
____ are neutron stars that have magnetic fields 100 times stronger than the average neutron star.
Magnetars

A neutron star is expected to spin rapidly because
they conserved angular momentum when they collapsed.

The density of a neutron star is
about the same as an atomic nucleus.

An isolated black hole in empty intergalactic space would be difficult to detect because
there would be no stars behind it whose light it could bend or lens gravitationally.
it could not emit light from inside its event horizon.
no companion stars would be affected by its gravitational field.
no  matter would be falling into it to create an x-ray emitting accretion disk.
all of the above

Hypernovae are
supernovae that occur when two red dwarfs collide.
supernovae that occur when 10 solar mass stars explode.
supernovae that occur when stars more massive than 25 solar masses explode.
one theory to explain the production of gamma ray bursters.
both c and d above

The mass of a neutron star is
several time that of the sun.

Why don't all supernova remnants contain pulsars?
All supernova remnants do contain pulsars.
Some supernova explosions form white dwarfs instead of the neutron stars necessary for pulsars.
Pulsars slow down and quit producing the pulses before the supernova remnant dissipates.
The pulsar may be tipped so that the beams do not sweep past Earth.
b and c

The event horizon
has a radius equal to the Schwarzschild radius.

A ____ has a radius of about 10 km and is supported by the pressure associated with degenerate neutrons.
neutron star

The escape velocity at the event horizon around a black hole is
equal to the speed of light.


Why does the rotation of our galaxy suggest that it is more massive than previously thought?
Ans: The mass of the galaxy can be found from its rotation curve. Kepler’sthirdlawreveals that
the galaxy contains over 1 trillion solar masses. However, the visible light from stellar radiation
only gives us 200 billion solar masses. To account for the difference, astronomers make a
hypothesis of dark matter that does not interact with the electromagnetic force, but whose
presence can be inferred from gravitational effect on visible matter.

1 comment:

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