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Review-Questions
(exam next Thursday, April 06
chapter 21-25)
Go Mason!
Go Through My Notes
CHAP21
Stellar Evolution:
After the Main Sequence
Question 1:
•
What is happening in the interior of a star that is on the main sequence on the HertzsprungRussell diagram? </div>
•
A. Stars that have reached the main sequence have ceased nuclear “burning” and are
simply cooling down by emitting radiation.
•
B. The star is slowly shrinking as it slides down the main sequence from top left to bottom
right.
•
C. The star is generating energy by helium fusion, having stopped hydrogen
•
D. The star is generating internal energy by hydrogen fusion.
(D)
Question 2:
• Over which of the following stages of stellar
evolution does the radius of a star remain
approximately constant?
•
•
•
•
A. birth and initial formation
B. red giant
C. asymptotic giant branch phase
D. main-sequence phase
(D)
Question 3:
• Which of the following statements about the mass and lifetime of
a star is true?
• A. Stars of about one solar mass have the shortest lives; less
massive stars evolve slowly and live a longer time, whereas
more massive stars have long lives because of the large amount
of fuel they contain.
• B. The more massive the star, the faster it will evolve through its
life.
• C.The mass of a star has no bearing on the length of a star's life
or the speed of its evolution.
• D. The less massive the star, the shorter its life, because it has
less hydrogen
(B)
Question 4:
• At which phase of a star's life will nuclear fusion
reactions that convert helium into carbon and oxygen
in the central core of a star occur?
• A. during and immediately after the (first) red giant or
supergiant stage
• B. during the protostar stage, before the main
sequence
• C. in the red giant stage, before the helium flash
• D. after the main-sequence phase, before the star
becomes a red giant
(A)
Question 5:
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•
•
•
•
A helium flash occurs in the cores of all stars
A. that contain helium.
B. of more than 2 solar masses.
C. of fewer than 2 solar masses.
D. that have become red giants.
(C)
Question 6:
• The “turnoff” point for a star cluster is the
point in the H-R diagram occupied by the
• A. highest-mass main-sequence stars in the
cluster.
• B. stars undergoing (or about to undergo) the
helium flash.
• C. lowest-mass main-sequence stars in the
cluster.
• D. highest-mass stars that have not yet
reached the main sequence.
(A)
Question 7:
• What characteristic of Cepheid variables makes them
extremely useful to astronomers?
• A. Their absolute magnitude is related directly to their
metal content (heavy element abundance).
• B. Their absolute magnitude is directly related to their
diameter.
• C.Their absolute magnitude is related directly to their
period of pulsation.
• D.Their absolute magnitude is related directly to their
surface temperature.
(C)
Question 8:
• Which factor, more than any other, modifies
the evolutionary tracks of stars in binary
combinations compared to their single star
counterparts?
• A. tidal distortion of the shapes of the stars
• B. radiation from one star heating the surface
of the second star
• C. mass exchange between the stars
• D. reduction of the quantum mechanical
limitation on continued shrinking of one star
by the gravitational field of the second star
(C)
CHAP22
The Death of Stars
Question 1:
• Which physical phenomenon keeps a white
dwarf star from collapsing inward on itself?
• A. electron degeneracy or “quantum
crowding”
• B. normal gas pressure
• C. convection currents or updrafts from the
nuclear furnace
• D. the physical size of the neutrons
(A)
Question 2:
• A sequence of thermonuclear fusion processes inside
massive stars can continue to transform the nuclei of
elements such as carbon, oxygen, etc. into heavier
nuclei AND also generate excess energy, up to a limit
beyond which no further energy-producing reactions
can occur. The element that is produced when this
limit is reached is
• A. silicon.
• B. oxygen.
• C. uranium.
• D. iron.
(D)
Question 3:
• The object seen at the center of a planetary
nebula is
• A. an accretion disk around a black hole.
• B. a planet in the process of forming.
• C. composed almost entirely of neutrons, and
is spinning rapidly.
• D.the former core of a red giant star, now a
white dwarf star.
(D)
Question 4:
• A Type II supernova is the
• A. explosion of a single massive star after
silicon burning has produced a core of iron
nuclei.
• B. explosion of a red giant star as a result of
the helium flash in the core.
• C. collapse of a blue supergiant star to form a
black hole.
• D. explosion of a white dwarf in a binary star
system after mass has been transferred to it
from its companion.
(A)
CHAP23
Neutron Stars
Question 1
• A pulsar is most probably formed
• A. in the core of a star as it evolves through
its main sequence phase.
• B. in the center of a supernova explosion.
• C. within a huge gas cloud, by collisions
between stars.
• D. just after the formation of a protostar by
gravitational condensation.
(B)
Question 2
• Synchrotron radiation is emitted whenever
• A.charged particles are forced to move along
curved paths within a magnetic field.
• B. matter and antimatter meet and annihilate.
C.charged particles are accelerated in
straight lines into dense gas such as the
outer atmosphere of a star.
• D.charged particles move at speeds faster
than the speed of light in any medium.
(A)
Question 3
• The fastest pulsars, called millisecond pulsars, have periods of
about 1/1000 second. The reason they pulse so much faster
than (for example) the Crab and Vela pulsars is that they
• A. were formed from much more massive stars than were the
Crab and Vela pulsars, and were spun up more as their cores
collapsed to a smaller volume.
• B.are normal pulsars, whereas the Crab and Vela pulsars have
been slowed down from millisecond speeds over their long
lifetimes. C. are a totally different phenomenon, involving a
black hole rather than a neutron
• D. were spun up by mass transferred on to them from a
companion in a binary star system.
(D)
Question 4
• The nova phenomenon, an occasional and sometimes repeated
intense brightening of a star by a factor of about 106, is caused
by
• A. the beam of radiation from a nearby pulsar illuminating the
surface of a red giant star and inducing rapid and intense
heating.
• B. hydrogen “burning”; explosively on the surface of a white
dwarf star after mass transfer from a companion star in a binary
system.
• C. the capture and rapid compression of matter by a black hole.
• D. the explosion of a single massive star at the end of its
thermonuclear burning phases.
(B )
CHAP24
Black Holes
Question 1:
• Suppose you are in the Space Shuttle in orbit around the Earth
at a speed of 7 km/s, and at some particular time your direction
of travel is straight toward the Sun. The speed of light in a
vacuum is 300,000 km/s. What speed will you measure for the
light from the Sun?
• A. 300,000 km/s
• B. 300,014 km/s because your speed is added to that of the light
and relativistic contraction has shortened your reference meter
sticks
• C. 299,993 km/s because relativistic contraction has shortened
all distances, including your reference meter sticks
• D. 300,007 km/s because your speed is added to that of the light
(A)
Question 2:
• What is the correct explanation of the bending of a beam of light
as it passes close to a massive object like the Sun?
• A. The gravitational field interacts with the electromagnetic field
of the photons to bend the light.
• B. It is traveling across and must follow the curved space
surrounding a massive object.
• C. The gravitational field of the massive object changes the
refractive index of the nearby space, leading to bending of the
light.
• D. The photons of light are attracted by the gravitational field of
the massive object.
(B)
Question 3:
• What is believed to be the maximum
mass for a neutron star?
• A.150 solar masses
• B.12 solar masses
• C.3 solar masses
• D.1.4 solar mass
(C )
Question 4:
• What is the event horizon of a black hole?
• A. the “surface” from the inside of which nothing can
escape
• B. the “surface” at which all “events” or activity
appear to happen because of general relativity
• C. the infinitesimally small volume at the center of the
black hole that contains all of the black hole's mass
• D. the “surface”; inside which any object entering will
leave with greater energy than that with which it
entered
(A)
Question 5:
• If you were watching a friend (or better still, an
enemy!) who has fallen as far as the event horizon of
a black hole, what would you measure as his
heartbeat (apart from effects caused by his
adrenaline level)?
• A. It would appear to be normal because gravity has
no effect on time intervals.
• B. It would appear to have slowed down somewhat,
but not much, because of the change of the speed of
light in the gravity field.
• C. It would appear to be zero, his heart would appear
to have stopped.
• D. It would appear to have speeded up to an
incredible rate.
( C)
CHAP25
Galaxy
Question 1:
• Interstellar matter blocks our view of the disk
of our galaxy
• A. not at all at any wavelength.
• B. more-or-less equally at all wavelengths
from radio waves to light waves.
• C. most at radio wavelengths, where
hydrogen absorbs radio waves efficiently, and
least at optical wavelengths.
• D. more at optical wavelengths, less in the
infrared, and not at all at radio wavelengths.
(D)
Question 2:
• What happens when the electron in a hydrogen atom
flips its direction of spin, from parallel to antiparallel to
that of the proton?
• A. Nothing;this is a forbidden transition and never
occurs.
• B. The atom emits a photon of 656.3 nm wavelength
(H alpha), in the red region of the spectrum.
• C. The atom emits a photon of 121.5 nm wavelength
(Lalpha), in the UV region of the spectrum.
• D. The atom emits a photon of 21-cm wavelength, in
the radio region of the spectrum.
(D)
Question 3:
• The speed of the Sun in its orbit around the
galaxy is deduced from observations of
• A. the galactic center, about which the Sun is
orbiting.
• B.Cepheid variables between spiral arms,
because distances can easily be measured to
them.
• C.the orbital motions of stars near the Sun.
• D. globular clusters in the galactic halo and
distant galaxies.
( D)
Question 4:
• What fraction of the mass of our galaxy
is in a form that we have been able to
see?
• A. about 10%
• B. 100%. Who ever heard of matter that
can't be seen?
• C. about 50%
• D. about 90%
(A )