the eclipses of the x-ray binary cygnus x-1 allow us to determine its
A distance
B mass
C age
D temperature
a black hole is an object
A from which nothing can escape
B whose escape speed is greater than the speed of light
C within which random motion is possible
D all of these
a black hole might result when
A a star 100,000 times more massive than the sun collapses
B a supernova explodes
C a white dwarf ages too much
D a galaxy collapses
a white dwarf, a neutron star and a black hole are roughly the size of ______, ______ and ______ respectively.
A the Earth, a large city, a point.
B a large city, the Earth, a point.
C a point, the Earth, a large city.
D the Earth, a point, a large city.
to about what size would the Earth have to be compressed to become a black hole?
A about a centimeter.
B about 10 kilometers.
C about 100 kilometers.
D the Earth could not become a black hole under any circumstances.
place the above objects in increasing order of density.
A black hole, neutron star, white dwarf.
B neutron star, black hole, white dwarf.
C white dwarf, neutron star, black hole.
D neutron star, white dwarf, black hole.
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.
the size of a stellar black hole is
A one inch
B two miles
C a hundred million light years
D any of the above
a black hole may have been "seen" as
A a star disappeared into it
B the cause of a supernova explosion
C x-rays emitted by matter falling into it
D it sucks in the light of a normal star behind it
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 in.
physics predicts that
A matter or energy can never enter a black hole
B nothing can stop the collapse of a stellar black hole
C black holes will "pop out" of our universe and be undetectable by any means
D pulsars are black holes
which of the following is not observational evidence that cygnus x-1 may b a black hole
A cygnus x-1 has a mass of about 9 solar masses
B x-rays are detected coming from cygnus x-1
C the cygnus x-1 x-ray source orbits around a dwarf star
D the radiation from cygnus x-1 varies very quickly, indicating that the sou is very small
according to Einstein's general theory of relativity, what will happen to an object thrown into a black hole after it crosses the schwarzschild radius?
A it is crushed into a singularity.
B it is thrown back at the speed of light.
C it is trapped forever.
D (a) and (b)
E (a) and (c)
a black hole might be indirectly observed by detecting
A gravity waves emitted as an object is pulled into it
B very high energy light waves which eventually leak out from it
C an empty spot in space
D its effect on the motion of stars
which of the following is not observational evidence that cygnus x-1 may be a black hole.
A cygnus x-1 has a mass of about 9 solar masses.
B x-rays are detected coming from cygnus x-1.
C the x-ray source orbits around a dwarf star.
D the x-ray radiation varies very quickly indicating that the source is very small.
a black hole is
A any object that has a density of 10**28 times the density of water
B any dark, dead star
C any object from which we could not escape with our most powerful current rocket
D any object whose minimum escape velocity is greater than the speed of light
one model for x-ray bursters involves
A matter accreting around a black hole.
B an accretion disk around a white dwarf in a binary.
C matter falling onto a neutron star in a binary.
D rapid pulsation of a neutron star.
E rapid rotations of a neutron star.
which of the following is not a theoretical characteristic of a black hole, according to the general theory of relativity?
A to an outside observer, an object falls into the black hole very quickly.
B an outside observer will never see an object reach the black hole.
C an observer falling into a black hole takes a very short time to reach the object at its center.
D an outside observer loses contact with an observer falling into a black hole when the
black hole boundary is crossed.
cygnus x-1 is one of the best candidates for a black hole. which of the following is not used in the array of observations to infer this result?
A cygnus x-1 emits x-rays.
B the optical counterpart is a blue supergiant star.
C Doppler shifts indicate an orbital period of 5.6 days.
D it is located in the constellation of cygnus.
light which strikes the surface of a black hole is
A totally reflected
B only partially reflected
C totally absorbed
D reflected before it reaches the surface
which of the following can escape from within a "black hole radius" of a black hole?
A photons
B anti-particles
C gamma rays
D none of the above or anything else, for that matter
black holes
A have been proven to exist by direct observation
B probably do not exist
C may be inferred to exist from recent observations
D can be produced in the laboratory
the following are ordered correctly with increasing size
A neutron star, stellar black hole, white dwarf, sun, red giant
B stellar black hole, neutron star, white dwarf, sun, red giant
C neutron star, stellar black hole, sun, white dwarf, red giant
D stellar black hole, white dwarf, sun, neutron star, red giant
there is good evidence that black holes have been detected
A by use of data concerning their chemical compositions.
B in binary systems.
C by observing planets falling into them.
D in planetary nebulae.
E in galactic clusters.
which effects have been useful in the search for and identification of black holes in the universe?
A the effect of their spin upon nearby matter
B the influence of their intense gravitational field upon atoms which are emitting light from the event horizons of the black holes
C their gravitational influence upon nearby matter, particularly companion s
D their magnetic fields and its influence upon nearby matter
the first candidate for a black hole was
A cygnus x-1.
B algol (the "demon star").
C sigma xi.
D centaurus a.
E xi ursa majoris.
if the sun could magically and suddenly become a black hole (of the same mass) the Earth would
A continue in its same orbit.
B be pulled closer, but not necessarily into the black hole.
C be pulled into the black hole.
D fly off into space.
if the entire universe is a black hole, which theory of cosmology would be favored
A Hubble's
B steady state
C single big bang
D oscillating or multiple big bang
binary x-ray sources are known to be binary because
A the two stars are observed visually as visual binary stars
B they are astrometric binaries
C eclipses are observed
D the name is a misnomer since no x-ray objects are known to be binary
an object which is believed to be a black hole in our galaxy is
A the central "star" in the crab nebula
B the central star in the ring nebula in Lyra
C the so-far undetected 10th planet in our solar system, because of its gravitational influence upon the outer planets
D cygnus x-1, a powerful x-ray source
all black holes are
A dense
B small
C collapsing
D none of these
a black hole is
A any black, nonreflective object
B an object from which nothing can escape
C a concentration of the matter of billions of stars
D the end point in the life of all stars
black holes definitely can be "observed" as
A quasars
B pulsars
C radio galaxies
D x-ray sources
which of the following probably has been seen indirectly as an x-ray source in the sky
A white dwarf
B neutron star
C black hole
D all of these
suspected black holes can be detected
A because they block our view of objects behind them
B from their black body radiation
C by x-rays emitted by the black hole
D by x-rays emitted by material swirling about the black hole
we can suspect that cygnus x-1 and lmc x-3 are black holes if the masses of the unseen companions are
A less than about 3 solar masses
B more than about 3 solar masses
C between 0.4 and 1.4 solar masses
D less than 0.4 solar mass
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 in
typically, black holes are recognized from their
A x-ray radiation
B radio signal
C visible light output
D ultraviolet radiation
whether a collapsed star is a white dwarf, a neutron star, or a black hole depends on its
A mass
B metal abundance
C helium abundance
D apparent brightness
the most massive stars are thought to end up as
A white dwarfs
B planetary nebulae
C neutron stars
D black holes
which of the following seems to rule out the theory that cygnus x-1 is a neutron star
A neutron stars could not emit x-rays
B if cygnus x-1 were a neutron star, it would have to be a pulsar, and that is not observed
C the mass of the object in cygnus x-1 is too large to be a neutron star
D neutron stars cannot exist in binary systems
which of the following lists the objects in order of decreasing maximum ma
A neutron star, white dwarf, black hole
B black hole, neutron star, white dwarf
C white dwarf, black hole, neutron star
D they all have approximately the same mass
in a black hole the density
A depends on the amount of material present
B is never very great
C is always tremendously large
D depends on the rest of the universe
black holes necessarily have
A high densities
B small size
C no random motion inside
D strong force of gravity
the velocity necessary to escape from a black hole is
A greater than or equal to the speed of light
B infinite
C undefinable
D less than the speed of light but very large
which of the following is necessarily a property of black holes
A immense mass
B high escape velocity
C immense density
D small size
x-rays which come from the vicinity of a black hole actually originate
A from relatively far away from the black hole, where matter is still relatively cool
B from its exact center, or singularity
C from just above the event horizon, on the accretion disk
D from well inside the event horizon
the escape velocity of matter from the center of a black hole whose mass I 3 solar masses is
A greater than the speed of light
B quite small
C relatively small, about 1/10 of the speed of light
D about half the speed of light
black holes were discovered in the real world by analysis of
A pulsar observations
B observations of white dwarfs
C events near the center of the milky way galaxy
D celestial x-ray sources
motion inside a black hole is
A impossible because of the large force of gravity
B impossible because of the high density
C greatly restricted and distorted
D not necessarily restricted except by the ordinary (that is, nonrelativistic) laws of physics
stellar black holes are observed by
A the x-rays emitted from matter being pulled in from a companion star
B the distortion of space around them
C their gravitational influence on the motion of objects near them
D their rapid collapse and disappearance
if an unseen component of a x-ray binary system has a mass greater than about 3 solar masses, theory tells us it must be a
A white dwarf
B neutron star
C black hole
D none of the above; no objects have unseen components, since we would not k of the
existence of such components!
which of the following can escape from a black hole?
A photons
B neutrinos
C gamma rays
D none of the above or anything else, for that matter
a black hole is defined to be any object whose minimum escape speed is
A infinite
B greater than the speed of light
C does not exist
D larger than is obtainable by any existing rocket
if black holes exist, we might expect them to form
A from stars that slowly cool off, becoming a cinder
B from stars whose cores are too massive to allow a neutron star to form when the core collapses
C from solar type stars when they stop giving off light
D from neutron stars that are less massive than white dwarfs
how might a celestial object be proven to be a black hole?
A by measuring its mass and diameter directly
B by measuring its gravitational effects on nearby material
C by noting that nothing comes out of it
D since a black hole emits no radiation of any kind, it is impossible to even detect one, let
alone prove anything about it
we can suspect that cygnus x-1 and lmc x-3 are black holes if the masses of the unseen companions are
A less than 3 solar masses.
B more than 3 solar masses.
C between 0.4 and 1.4 solar masses.
D less than 0.4 solar mass.
one feature which distinguishes a black hole from all other objects in the universe is that
A the escape velocity from this object is greater than the speed of light
B it emits large quantities of x-rays
C its total mass exceeds 3 solar masses
D the shape of its gravitational field is always different from that of an ordinary massive
object, even at large distances from it
if black holes exist, we might expect them to form from
A stars that slowly cool off, becoming cinders.
B stars whose cores are too massive to become neutron stars when they collapse.
C solar type stars when they stop giving off light.
D neutron stars that are less massive than white dwarfs.
supermassive black holes
A can only be formed when the most massive (70 or more solar masses) stars explode
B are less dense than "stellar" black holes formed in stellar supernova explosions
C might explain the violent activity in the cores of some galaxies (including our own) and in quasars
D both b and c
the observed x-rays that are thought to be coming from the region around a black hole are from
A the gas particles splatting on the surface of the black hole
B the singularity at the center of the black hole
C an accompanying white hole
D the hot gas of the accretion disk
matter tends to swirl about a black hole instead of falling straight in because
A the force of gravity is too strong
B there is always too much matter in the way
C it can survive longer before crossing the event horizon
D of its orbital motion around the black hole
imagine a rocket leaves the Earth with just the escape velocity from the Earth. which of these best describes its motion?
A the rocket slows down and falls back to Earth.
B the rocket speeds up as it moves out into space.
C the rocket slows down and has zero velocity far away.
D the rocket slows down and has some velocity far away.
far away from a black hole (say 50 light-years), which of the following is a way to detect it?
A notice how it blocks the star light from behind it
B look for the pulsed radio waves it gives off as it rotates like a light-house
C search for the x-rays it gives off as it eats away at a neighbor star
D you can't fool me; there is no way to detect a black hole from that faraway
an observer who, at a safe distance, watches an astronaut travel toward and into a black hole will see
A the astronaut reach the singularity in a short time.
B the astronaut never crossing the event horizon.
C light flashes sent by the astronaut blue shifted.
D light flashes sent by the astronaut arrive more and more rapidly.
E none of the above.
if the sun were suddenly to be replaced by a solar-mass black hole the gravitational force on Earth would
A double
B become so strong that the Earth would be "sucked" into the black hole
C decrease because black holes cause gravity at large distances to disappear
D remain the same
a supermassive black hole might form in the center of a galaxy
A from the central collapse of the gas that formed the galaxy
B from the merger of closely interacting stars
C after many supernovae create many small black holes, which then merge to form a single large black hole
D from the concentration of the unseen "missing matter" found there
for a 6 solar mass remnant of a star, what will stop the gravitational collapse
A heating of the gas from the collapse
B electron degeneracy
C neutron degeneracy
D none of the above
x-rays are emitted around a black hole when
A a star is pulled into the black hole
B new matter is created around the black hole
C individual atoms are pulled into the black hole
D star light is pulled into the black hole
a black hole must have
A a very high density
B a small size compared to a normal star
C a minimum escape velocity greater than the speed of light
D all of these
which of the following is not a result of the theory of relativity
A measurement of time is relative to the velocity of a moving object
B all motion is relative
C measurement of size and mass is relative to the velocity of a moving object
D energy and mass are interchangeable quantities
travel by humans in the fourth dimension (time)
A has probably already happened
B is a distinct possibility for the future
C cannot occur according to the current laws of physics
D is neither predicted or ruled out by physics
the fundamental principle of the special theory of relativity is that
A all velocities should be measured relative to a fixed luminiferous ether
B any physical experiment will give the same result in any unaccelerated system
C gravitation may be regarded as due to the curvature of space
D space and time are interchangeable coordinates in a four dimensional space-time
continuum
Einstein's special theory of relativity predicts that particles moving faster than the speed of light
A do not exist in our real universe
B are tachyons
C annihilate when they interact with normal matter
D might affect the orbits of the planets.
the theory of relativity predicts that in order to accelerate a material object to the speed of light
A gravity would have to be turned off
B an infinite mass would be required
C an infinite force would be required
D the object would have to be stronger than diamond
if a runner holding a flat mirror in front of himself could run at nearly the speed of light, he would
A immediately see his undistorted reflection
B see his reflection only after a long time interval
C see a greatly reduced reflection of himself
D not be able to receive any light at all
Einstein's first theory of relativity assumes that
A an upper limit to the speed of an object is the speed of light
B time and length are relative concepts
C that energy and mass are interchangeable
D that the speed of light in a vacuum is a constant
gravity waves can be detected by
A looking for the light given off by oscillating electrons
B measuring changes in the orbits of the planets
C measuring the oscillations of large objects
D no known phenomena
the bending of starlight by the gravitational field of the sun
A is much too small to ever observe
B should be observable but has not yet been detected
C has been detected
D should not exist
a space traveler moving away from the Earth at very high speed
A ages at a different rate than we do on the Earth
B seems to age at a different rate than we do on the Earth
C does not age at all until his return
D does not "see" any aging on the Earth at all
according to the theory of relativity which of the following is not relative quantity
A the speed of a rocket ship
B the speed of light sent from the rocket ship
C the size of the rocket ship
D the weight of the rocket ship
a light signal from a rocket ship moving away from the Earth at nearly the speed of light would reach the Earth at
A the rate of very nearly zero velocity
B twice the ordinary speed of light
C an unmeasurable rate because of the motion of the rocket ship
D 186,000 miles/sec
which of the following is not a consequence of the general theory of relativity
A the bending of light rays passing near to the sun
B the advance of the perihelion of Mercury
C the red shift of light from dense stars
D the conversion of matter to energy in the atom bomb
the special theory of relativity was developed principally by
A michelson and morley
B Lorenz
C Fitzgerald
D Einstein
the advance of the perihelion of Mercury can be used to test
A newton's laws
B Einstein's laws
C both (a) and (b)
D neither (a) and (b)
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