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.
answer
event horizon
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Observations from the Compton Gamma Ray Observatory showed that gamma-ray bursters were located throughout the sky. This told us that
answer
1) the bursts were not produced among stars in the disk of our galaxy.
2) the bursts were not produced among stars in the nuclear bulge of our galaxy.
3) the bursts are not associated with planets in our solar system.
4) the bursts were not produced in our Sun.
5) All of the above.
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Hypernovae are
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3) supernovae that occur when stars more massive than 25 solar masses explode.
4) one theory to explain the production of gamma ray bursters.
5) both 3 and 4 above.
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____ occurs when light travels out of a gravitational field, loses energy and its wavelength grows longer.
answer
A gravitational redshift
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A ____ has a radius of about 10 km and is supported by the pressure associated with degenerate neutrons.
answer
neutron star
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A neutron star is expected to spin rapidly because
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they conserved angular momentum when they collapsed.
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____ are neutron stars that have magnetic fields 100 times stronger than the average neutron star.
answer
Magnetars
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The slowing of clocks in strongly curved space time is known as
answer
time dilation.
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Although neutron stars are very hot, they are faint and not easy to see at visual wavelengths because
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3) they have only a small surface area from which to emit.
4) the peak of their thermal emission is at much shorter wavelengths than visual.
5) both 3 and 4.
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In A.D. 1054, Chinese astronomers observed the appearance of a new star, whose location is now occupied by
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a pulsar.
a neutron star.
a supernova remnant.
all of the above.
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Pulsars cannot be spinning white dwarfs because
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a white dwarf spinning that fast would fly apart.
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Similar to our Sun, pulsars' rotations are believed to slow down because
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they are losing angular momentum into space via outward streaming particles.
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The event horizon
answer
has a radius equal to the Schwarzschild radius.
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An isolated black hole in empty intergalactic space would be difficult to detect because
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1) there would be no stars behind it whose light it could bend or lens gravitationally
2) it could not emit light from inside its event horizon
3) no companion stars would be affected by its gravitational field
4) no matter would be falling into it to create an x-ray emitting accretion disk
5) All of the above
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Cygnus X-1 and LMC X-3 are black holes if the masses of the unseen companions are
answer
more than 5 solar masses.
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The peculiar system SS 433
I. is emitting beams of energy and matter.
II. is producing a spectrum with both a red and a blue shift.
III. probably contains an accretion disk.
IV. is the result of a planetary nebula.
answer
I, II, & III
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Which of the following objects is considered to possibly contain a black hole?
answer
LMC X-3
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The orbit of the binary pulsar, PSR 1936+16, studied by Taylor and Hulse
answer
is growing smaller, presumably by emitting gravitational waves.
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The density of a ____ is greater than the density of a ____.
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pulsar, white dwarf
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The search for black holes involves searching for
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X-ray binaries where the compact companion has a mass in excess of 3M
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The material that accretes onto a neutron star or black hole is expected to emit X-rays because
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the material will become hot enough that it will radiate most strongly a X-ray wavelengths.
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Why don't all supernova remnants contain pulsars?
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The pulsar may be tipped so that the beams do not sweep past Earth.
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Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?
answer
1) Science requires that experimental and theoretical findings be reproducible.
3) Scientific results are reviewed by other scientists before they are published.
5) 1 and 3 above.
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As material flows into a black hole
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the material will experience time dilation.
the material will become hotter.
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The first pulsar was discovered by ____ in November of 1967.
answer
Jocelyn Bell
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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.
answer
I, III, & IV
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None of the pulsars emit pulses of visible light because
answer
A few pulsars do emit visible light pulses.
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Millisecond pulsars that are very old are
answer
believed to be the result of mass transfer from a companion that increases the spin of the pulsar.
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The Schwarzschild radius of a 1M black hole is approximately
answer
3 km.
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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.
answer
I & III
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The singularity of a black hole
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is located within the event horizon.
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The escape velocity at the event horizon around a black hole is
answer
equal to the speed of light.
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Which of the following can you never know about a black hole?
answer
The elements of the material that has fallen in.
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Neutron stars have densities roughly the same as that of the atomic nucleus.
answer
True
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Neutron stars were first discovered in the 1930's.
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False
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Pulsars could not be pulsating stars because the pulses are too short.
answer
True
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We expect neutron stars to spin rapidly because they conserve angular momentum.
answer
True
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Many pulsars have periods that are gradually increasing as the spinning neutron stars lose energy.
answer
True
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The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus.
answer
False
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Theory predicts that neutron stars may not exceed 3 solar masses.
answer
True
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If the accretion disk around a black hole emits X-rays outside the event horizon, the X-rays can escape.
answer
True
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To tell the difference between a neutron star and a black hole in an X-ray binary, we must find the temperature of the object.
answer
False
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LMC X-3 is a binary system that is believed to contain a black hole.
answer
True
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A scientific theory can be proven true if the correct experiments are performed.
answer
False
question
When a star, of mass comparable to the Sun, dies it become a black hole.
answer
False
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