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80 Cards in this Set
- Front
- Back
The periods of Cepheid variable stars are straightforwardly related to their corresponding
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luminosities
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The escape velocity is greater than the speed of light
within |
a black hole.
a Schwarzschild radius. an event horizon. |
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The value of a Schwarzschild radius is dependent upon
the initial _______ of a collapsing stellar core ("stellar corpse"). |
mass
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Suspected candidates for stellar black holes are detected _________ in a binary star system.
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indirectly as x-ray sources
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The Sun is a member of the Milky Way galactic
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disk
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Observation of distant parts of the Milky Way Galaxy
would be severely limited if used only the visible part of the electromagnetic spectrum. Why? |
interstellar dust blocks visible light
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Radio observations can provide information about the
Milky Way Galaxy that we cannot learn from observations in visible light because |
radio waves are able to pass through clouds of dust
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At a distance of 10 kpc from the center of the Milky Way Galaxy, the Sun takes 225 _______ to complete one orbit.
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million years
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Due to a departure from _________, astronomers have concluded that there is a lot of dark matter in the galactic halo.
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kepler's third law
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halo stars follow
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RANDOMLY INCLINED,
APPROXIMATELY CIRCULAR ORBITS. |
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As a galaxy ages, the percentage of heavier elements
in the newer stars should |
increase
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The density of stars is highest in the galactic
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nucleus
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The Milky Way and the Andromeda Galaxy will collide in about five _______.
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billion years
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The core or nucleus of the Milky Way Galaxy shows evidence of the current existence of a ______ Thus, billions of years ago, the Milky Way would have looked like a ________
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supermassive black hole; quasar
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Cepheid variables are important in calculating
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the distances to galaxies
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Hubble found that the objects that were first called
spiral nebulae are instead spiral galaxies. He achieved this by observing |
cepheid variables in them
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Measurements of the total mass in clusters of galaxies indicate that they contain far more mass than is visible to us. The "missing mass" is now known to be
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cold dark matter
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The Sun is one of about how many stars in the Milky Way Galaxy?
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400 billion
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The Milky Way is a member of a cluster of about _______ called the Local Group.
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30 galaxies
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The Large and Small Magellanic Clouds are
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small nearby galaxies
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The Andromeda Galaxy (M31) is a member of a cluster of _______ called the Local Group
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30 galaxies
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Observations of the ______ of Cepheids in distant galaxies are used to determine the distances
of those galaxies. |
distances and apparent magnitudes
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A megaparsec is equal to
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10^6 parsecs
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The look-back time for a galaxy 1 Mpc away is equal
to 3.26 _______ years. |
million
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Hubble's constant has units of
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VELOCITY DIVIDED BY DISTANCE,
NAMELY, (KM PER SECOND)/MPC. |
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Hubble's law applies to
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individual clusters of galaxies
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The galaxy type with the largest number of stars consists of
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elliptical galaxies
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The Milky Way is
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a barred spiral galaxy
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When galaxies "collide," the individual stars
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mostly do not collide
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The famous neighboring Andromeda galaxy is
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a normal spiral galaxy
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The lobes of a radio galaxy are ______ the visual component of the galaxy
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much larger than
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Quasars, radio galaxies, and Seyfert galaxies are examples of
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active galaxies
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The large redshifts observed in the spectra of quasars
indicate that they appear to be _____ at great velocities. |
receding
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Hubble's-law interpretation of the quasars is that they are
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far away and moving away quickly
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A quasar with a z value of 10 is moving _______ the speed of light.
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AT AN APPRECIABLE FRACTION
OF |
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According to Olbers's paradox, if the Cosmos had ex-
isted forever, then the night sky would be |
bright and hot
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The Big Bang or primordial explosion occurred approximately _______ years ago.
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14 billion
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The age of the universe is approximately _____ years old
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14 billion
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A closed Universe, with spherical geometry, starting
with a Big Bang and ending with a Big Crunch, is one in which the average density is ______ the critical density. |
greater than
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an open universe is one that
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will never stop expanding
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present knowledge indicates that the universe
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is open
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If the average density of the universe were smaller
than the critical density, the universe would be |
negatively curved and open
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The measured primordial or cosmic background radiation can be explained by
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the big bang model
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If galaxy X is four times more distant than galaxy Y,
then according to Hubble's law, galaxy X appears to be receding |
four times faster
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The main observational problem in determining the
Hubble constant for galaxies at great distances lies in the measurement of their _____. This problem has been overcome (but only in the past 15 years!) with the systematic use of Type Ia supernovae as standard candles. |
distance
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The primordial nucleosynthesis predicted by the laws
of nuclear/particle physics provides the overall proportions of ______ and other light elements in the Cosmos (such as lithium-7). These values are in excellent agreement with their observed counterparts. |
hydrogen, helium
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Only one of the following is not manifestly support-
ing evidence in favor of the Big Bang (it does not contradict it either). |
galactic rotation curves
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What is the primary form of evidence that has led
astronomers to conclude that the expansion of the universe is accelerating? |
observation of type Ia supernovae
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The determination of distances to far-away galaxies
has led to the conclusion that the universe is expanding at |
an accelerated rate
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The fact that the universe is "accelerated" is explained by the assumption that it contains large amounts of "exotic stuff" known a
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dark energy, vaccuum energy, quintessence, cosmological-constant energy
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The list of all distinct fundamental interactions of the present Cosmos consists of
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weak, strong, electromagnetic, and gravitational
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The weak (nuclear) force is responsible for
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radioactivity and cosmic alchemy
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the strong (nuclear) force is responsible for
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THE BINDING OF QUARKS IN-
SIDE PROTONS AND NEUTRONS, AS WELL AS THE BINDING OF PROTONS AND NEUTRONS INSIDE THE NUCLEUS. |
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A proton is made up of more elementary particles known as
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up and down quarks
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The list of all distinct fundamental interactions during the era of "grand unication" (before 10
35 seconds after the Big Bang) is thought to consist of (a) gravitational interaction (1 force). |
GRAND-UNIFIED ELECTRONU-
CLEAR FORCE AND GRAVITATION (2 FORCES). |
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The inflationary model of the Big Bang provides an early period of exponential inflation at about 10^-35 seconds after the Big Bang. This inflation is qualitatively reminiscent of (but more dramatic than) the
current ______ of the Cosmos and is also due to ______. |
ACCELERATION;
A COSMOLOGICAL CONSTANT |
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Our current knowledge of the early Cosmos can be extrapolated, with more or less precision, to almost the
end of the Planck era. This is the era when all the fundamental interactions, even gravity, were unified. However, our best theories fail there: we have candidates known as quantum gravity, superstrings, etc, but space and time cease to have their usual meaning. The end of this era is where science ends and speculation begins; this time happened approximately _____ after the Big Bang! |
10^-43 seconds
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The Tully-Fisher method of measuring distances to spiral galaxies depends on the relationship between a galaxy's absolute magnitude (luminosity) and its
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rotation rate
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the horizon and flatness problems
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ARE SOLVED BY THE INFLATION-
ARY MODEL OF THE BIG BANG. |
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As the universe cooled, it eventually reached a temperature of 3,000 K and protons were able to capture and hold electrons to form neutral hydrogen. This process is known as
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recombination
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the cosmological background radiation is
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the redshifted radiation from the
time atoms were first formed in the early universe. |
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In the early universe
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Only light elements were synthesized.
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Which of the following statements denes what we mean by dark energy?
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It is a name given to whatever
is causing the expansion of the universe to accelerate with time. |
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Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?
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Dark matter is the dominant form of mass in both clusters and in individual galaxies.
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What is the distinguishing characteristic of what we call ordinary or baryonic matter?
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It consists of atoms or ions with
nuclei made from protons and neutrons. |
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Some matter may consist of what astronomers call
MACHOs (massive compact halo objects). Which of the following would not be considered a type of MACHO if it were found in the halo of the galaxy? |
neutrino
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When we speak of the large-scale structure of the universe, we mean
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the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe.
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Which of the following best sums up current scientic
thinking about the nature of dark energy? |
Dark energy probably consists of
the quantum fluctuations of the vacuum. |
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The event horizon of a black hole that results from the collapse of a 5MSun body will be
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15 km in radius
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The beautiful red supergiant Betelgeuse is a single star with a mass of approximately 17MSun this qualifies it as a "heavyweight." What is its eventual fate?
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It will produce a supernova and
leave behind a black hole. |
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Which of the following is not a piece of observational evidence that one of the bodies in the binary system Cygnus X-1 is a black hole?
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The companion star is an "old"
supergiant. |
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X-rays emitted from the vicinity of a black hole actually originate
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from just above the event horizon, on the accretion disk.
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Imagine that our Sun were suddenly replaced by a
black hole of the same mass (1 solar mass). What would happen to the Earth in its orbit? |
Nothing- the Earth's orbit would remain the same
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X-rays emitted from the vicinity of a black hole actually originate
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from just above the event horizon, on the accretion disk.
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What do we mean by the singularity of a black hole?
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It is the center of the black hole,
a place of infinite density where the known laws of physics break down. |
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Which statement concerning black hole masses and Schwarzschild radii is not true?
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In a binary system with a black
hole, the Schwarzschild radius depends on the distance from the black hole to the companion star. |
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Consider a black hole, surrounded by an accretion disk, in a close binary star system. One foolhardy
day, a daring space traveller decides to become a hero by crossing the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least to start the process of killing him first)? |
X-rays from the accretion disk.
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Consider a binary star system consisting of a 30MSun black hole and a 70MSun red supergiant. They orbit about their common center of mass in 1/10 of a year
(i.e., say, 36.5 days) in approximately circular orbits. What is their separation distance a in AUs? |
1 AU
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The relative wavelength change =0 of a receding galaxy (i.e., moving away from us) is 10%. What is the recession speed of this galaxy?
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c/10
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Suppose that we know that a galaxy 5 million lightyears away is receding at 20 miles per second. What would be the Hubble constant based on this single
galaxy |
(4 mi/s)/mly
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