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Physics 130
Astronomy
Exam 3
August 11, 2004
Name:______________________________
1._____The final remnant of the evolution of a red giant star that has ejected a planetary
nebula is
a.) a blue super giant
b.) a protostar
c.) a white dwarf star
d.) a supernova
2._____A white dwarf star is about the same size as
a.) the total solar system
b.) a major city
c.) the Earth
d.) the Sun
3._____A white dwarf star is supported from collapse under gravity by
a.) pressure of the gas, heated by nuclear fusion reactions in its core.
b.) pressure of the gas, heated by nuclear fusion reactions in a shell around its
core.
c.) centrifugal force due to rapid rotation.
d.) degenerate-electron pressure in the compact interior.
4._____Which force induces the core to condense and collapse in massive stars at the
conclusion of each episode of nuclear fusion, such as carbon, oxygen and silicon
fusion cycles?
a.) The nuclear attractive force between nuclei and between neutrons and protons.
b.) Gravity
c.) Electron degeneracy pressure
d.) Gas pressure produced by the very high gas temperatures.
5._____What is a pulsar?
a.) A pulsating white dwarf star, fluctuating rapidly in brightness.
b.) Very hot material orbiting a black hole.
c.) A Cepheid variable star with a period of a few days.
d.) A rapidly rotating neutron star, producing beams of radio energy and
occasionally of x-rays and visible light
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6._____A black hole is so named because
a.) it emits no visible light because it is cold, less than 10K.
b.) its spectrum has the same shape as that of a laboratory black body, typically at
a temperature of about 150K.
c.) no light can escape from it because of its powerful gravitational field.
d.) the gravitational field is so high that the wavelength of the emitted light is
shifted to radio wavelengths.
7._____What is the escape velocity from inside a black hole?
a.) Zero
b.) Greater than the speed of light
c.) Infinite
d.) Twice that from a neutron star
8._____X-rays that come from the vicinity of a black hole actually originate
a.) from well inside the event horizon
b.) from just outside the event horizon, on the accretion disk
c.) from its exact center, or singularity
d.) from relatively far away from the black hole, where matter is quite cool.
9._____Variable stars, such as Cyheid variables and RR Lyrae stars, are used in what
important measurement in astronomy?
a.) The measurement of the rotation speeds of galaxies.
b.) The keeping of accurate time.
c.) The measurement of the distances to stars.
d.) The measurement of the surface temperatures of stars.
10._____Galaxies throughout the Universe appear to be distributed
a.) mostly in the single spherical shell surrounding a void in space, presumed to
to have been caused by a vast explosion.
b.) uniformly throughout space.
c.) in groups and surfaces surrounding vast voids, much like the surfaces of giant
bubbles.
d.) Around a single point in space, the presumed location of the original Big
Bang, which created the Universe.
11._____Which component of our galaxy accounts for interstellar extinction, the
dimming of light from distant objects?
a.) Molecules such as H2 and CO, which are strong absorbers, in molecular
clouds.
b.) the so-called hidden or missing matter, since its absorbing properties render it
invisible in the galaxy.
c.) Dust.
d.) Cool hydrogen gas.
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12._____Where in space would you look for a globular cluster?
a.) In the Milky Way galactic halo, orbiting the galactic center in a long
elliptical orbit around the galactic center.
b.) Only in elliptical galaxies, since they are composed of old stars and do not
exist in young systems like spiral galaxies.
c.) In the Milky Way disk, moving in a circular orbit around the galactic center.
d.) In the asteroid belt.
13._____How is cool, neutral hydrogen gas, HI, detected in the spiral arms of galaxies?
a.) By its Balmer line emissions.
b.) By the absorption of infrared radiation from extragalactic sources
c.) By its 21 cm line radio emissions.
d.) By its ultraviolet, Lyman a, hydrogen line emissions.
14._____Where is the solar system located in our galaxy?
a.) In the galactic disk.
b.) In the galactic halo.
c.) It is not in a galaxy, but in the intergalactic space between galaxies.
d.) In the galactic nucleus.
15._____Which parameter is plotted as a function of distance from the galactic center in
a rotation curve of a galaxy?
a.) The speed of stars orbiting the galactic center.
b.) The thickness of the galactic disk.
c.) The mass of matter inside the distance from the galactic center.
d.) The mass of cool hydrogen gas.
16._____The center of our Milky Way Galaxy can be observed most easily at which of
the following electromagnetic wavelengths?
a.) Ultraviolet radiation
b.) Infrared and radio waves
c.) Visible light
d.) High-energy gamma rays
17._____What is the name given to a galaxy with a smooth distribution of brightness and
a round shape?
a.) SBa
b.) Sa
c.) EO
d.) E7
18._____What does a spiral galaxy look like when seen edge-on?
a.) A thick, flat line with a bulge in the center.
b.) Round but without spiral arms because they are hidden.
c.) A thick, flat line.
d.) A thick line curved into a spiral shape.
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19._____In which of the following types of galaxies is star formation no longer
occurring?
a.) Elliptical galaxies
b.) Irregular galaxies
c.) Spiral galaxies
d.) Bared spiral galaxies
20._____The Local Group is
a.) a cluster of galaxies in which the Milky Way is located.
b.) the family of planets around the Sun.
c.) the name of the spiral arm of our Galaxy in which the Sun is located.
d.) A star cluster to which the Sun belongs.
21._____What is believed to be the origin of giant elliptical galaxies?
a.) They grow by devouring smaller galaxies.
b.) The have grown continuously since their formation, by accretion of
intergalactic gas.
c.) They formed that way and have remained unchanged ever since.
d.) Collisions of galaxies in the cluster produces a smooth distribution of stars
through the cluster, which sink to the center of the cluster and form giant
galaxies there.
22._____Dark, unknown forms of matter appear to make up about what fraction of the
mass of a typical rich cluster of galaxies?
a.) Half
b.) 90%
c.) 10%
d.) Much less than 1%
23._____Which two quantities are known to be related to one another in Hubble’s Law?
a.) Distance and brightness
b.) Distance and recession velocity
c.) Brightness and recession velocity
d.) Brightness and the width of the 21 cm radio emission line of hydrogen.
24._____Suppose a galaxy is 400 million parsecs from the Earth. What is the recessional
velocity of this galaxy? Assume Hubble’s consant to be 80 km/s/Mpc.
a.) 5 million km/s
b.) 200,000 km/s
c.) 5 km/s
d.) 32,000 km/s
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25._____”Standard candles”, which are important for finding distances to remote
galaxies, are
a.) stars and other objects of known intrinsic brightness.
b.) standard laboratory light sources with which the brightness of a galaxy can be
compared.
c.) heat sources used for calibrating infrared observations of galaxies.
d.) standard bars of known length with which the size of a galaxy can be
measured.
26._____Astronomers initially had difficulty identifying the emission lines in quasar
spectra at optical wavelengths because
a.) no one expected to see ultraviolet spectral lines in the visible region.
b.) the lines are created by elements which do not exist on Earth.
c.) they were emission lines from ionized atoms which had not been seen before.
d.) the emission lines were smeared out by the extremely high speed of the
quasars, making them hard to measure.
27._____Evidence obtained over the last few years indicates that quasars are most
probably
a.) the remnant cores of exploding stars are supernovae
b.) evidence of very intense star-building activity in certain distant dust and gas
clouds.
c.) The focused effect of a closer galaxy.
d.) The central nuclei of very distant, very active galaxies.
28._____The “central engine” of an active galaxy appears to be
a.) supernova explosions in an extremely dense star cluster at the center of the
galaxy.
b.) the violent merger of two galaxies, in which the collision throws out jets of
matter along the rotation axis of the larger galaxy.
c.) a supermassive black hole at the center of an accretion disk, with material
being projected out perpendicular to the disk.
d.) stars falling into a supermassive black hole, their remnants being thrown out
in all directions.
29._____In relation to the universe, what does “isotropy” mean?
a.) The expansion is the same in all directions.
b.) The speed of expansion is the same at all distances.
c.) The speed of expansion at any given distance is the same at all times.
d.) The universe is the same everywhere, neither expanding nor contracting.
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30._____Which one of the following statements is a correct description of the expansion
of the universe?
a.) Space is a vacuum, but the vacuum has real properties, as galaxies (or
superclusters of galaxies) hurtle outwards, the expansion is gradually slowing
down by the resistance of space to the passage of the galaxies.
b.) Space time is static, but exerts an outwards pressure on the galaxies in it,
this pressure is accelerating the galaxies (or superclusters of galaxies)
outwards through space time and away from each other.
c.) Space time is something real, with galaxies inside it; as space time expands,
the galaxies (or superclusters of galaxies) are carried along by expansion.
d.) Space is a vacuum, which is really nothing at all; the galaxies (or
Superclusters of galaxies) are hurtling outwards through this nothingness.
31._____What major problem would arise if the value of Hubble’s constant turned out to
to be 100 km/s/Mpc?
a.) Galaxies would be traveling too fast for the Universe to be gravitationally
bound.
b.) Galaxies would be traveling faster than observations allow.
c.) The age of the Universe would be less than the ages of some of the stars in it.
d.) Some galaxies would be farther away than the edge of the Universe.
32._____What is the cosmic microwave background radiation?
a.) An almost uniform background of radiation from distant, unresolved,
overlapying galaxies.
b.) a uniform background of radiation from electrons spiraling in weak
intergalactic magnetic fields.
c.) Radiation left over from the Big Bang, after the universe expanded and
cooled.
d.) Radiation from a very tenuous, ionized gas that fills the universe equally in all
directions.
33.______What are the particles that make up protons and neutrons?
a.) Quarks
b.) Neutrinos
c.) Muons
d.) Gravitons
34._____In high energy physics, when two gamma ray photons meet, they can
a.) produce a huge number of low-energy photons.
b.) disappear, creating two negative electrons.
c.) disappear, creating a particle-antiparticle pair.
d.) disappear completely, leaving nothing behind.
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35._____In the present theory of the Big Bang, what significant event occurred at
roughly 1 million years after the universe starting expanding?
a.) The universe became transparent to photons of radiation
b.) The universe became transparent to neutrinos.
c.) The primordial helium in the universe was produced.
d.) The temperature of the cosmic background radiation had cooled to its present
level of about 3K.
36._____What condition is necessary for the universe to be unbounded (infinite in
extent)?
a.) The density of the universe must be greater than some critical value.
b.) The density of the universe must be equal to some critical value.
c.) The density of the universe must be less than some critical value
d.) The universe must have no mass in it.
37._____What kind of curvature (geometry of space) does the universe have if the
universe is just bounded?
a.) Flat
b.) Spherical
c.) Parabolic
d.) Hyperbolic
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TRUE OR FALSE:
38._____White dwarfs have masses between 2 and 3 solar masses.
39._____Since a nova explosion tends to destroy the exploding star, a given star can
become a nova only once.
40._____At a black hole singularity, density and pressure become zero.
41._____The entire Milky Way Galaxy rotates like a solid body, that is, like a rotating
plate.
42._____The density of stars in the galactic disk is nearly the same in the spiral arms as
between them.
43._____The Sun appears red at sunset because the blue light has been scattered away by
the Earth’s atmosphere.
44._____Young stars in our Galaxy tend to be found in the galactic halo.
45._____Globular clusters are Population II objects.
46._____All known galaxies have sizes and masses near the values for the Milky Way
galaxy.
47._____An EO galaxy is more flattened than an E7 galaxy.
48._____The temperature of the 3K background radiation is 10K.
49._____If quasars are at great distances, we see them as they were when the universe
was young.
50._____The statement that the structure of the universe is the same everywhere is the
assuption of universality.
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