Question 40 (1 point)

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Momentum is defined as

Question 40 options:

	force multiplied by velocity.
	mass multiplied by acceleration.
	mass multiplied by speed.
	mass multiplied by velocity.

Question 41 (1 point)

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Suppose you lived on the Moon. Which of the following would be true?

Question 41 options:

	Both your weight and your mass would be less than they are on Earth.
	Both your weight and your mass would be the same as they are on Earth.
	Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
	Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth.

Question 42 (1 point)

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Newton's Second Law of Motion tells us that the net force applied to an object equals its

Question 42 options:

	mass multiplied by velocity.
	momentum multiplied by velocity.
	mass multiplied by acceleration.
	mass multiplied by energy.

Question 43 (1 point)

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The energy attributed to an object by virtue of its motion is known as

Question 43 options:

	potential energy.
	kinetic energy.
	radiative energy.
	mass-energy.

Question 44 (1 point)

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When an atom's electrons fall down to lower energy levels in a thin cloud of hot gas, what is produced?

Question 44 options:

	an infrared spectrum
	thermal radiation
	new interstellar compounds
	an emission line spectrum
	an absorption line spectrum

Question 45 (1 point)

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We know the Sun is primarily made from hydrogen and helium on the basis of its

Question 45 options:

	age.
	color.
	mass.
	luminosity.
	spectrum.

Question 46 (1 point)

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Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

Question 46 options:

	Its surface is cooler than the surface of the Sun.
	It is moving away from us.
	It is much more massive than the Sun.
	It is much brighter than the Sun.

Question 47 (1 point)

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We know how fast a distant galaxy is moving away from us on the basis of its

Question 47 options:

	luminosity.
	color.
	spectrum.
	mass.
	age.

Question 48 (1 point)

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We can see the Moon because it

Question 48 options:

	emits thermal radiation.
	emits visible light.
	reflects infrared light.
	reflects visible light.
	glows through radioactive decay.

Question 49 (1 point)

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What is the difference between energy and power?

Question 49 options:

	Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
	Power is measured in joules and energy is measured in watts.
	Power is used to describe energy of light, whereas the term energy has a broader meaning.
	There's no difference; energy and power are different names for the same thing.

Question 50 (1 point)

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According to modern science, approximately how old is the Sun?

Question 50 options:

	4 1/2 billion years
	10,000 years
	25 million years
	400 million years

Question 51 (1 point)

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The source of energy that keeps the Sun shining today is

Question 51 options:

	gravitational contraction.
	nuclear fusion.
	chemical reactions.
	nuclear fission.

Question 52 (1 point)

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When we say that the Sun is a ball of plasma, we mean that

Question 52 options:

	the Sun is made of atoms and molecules.
	the Sun is roughly the same color as blood.
	the Sun is made of material that acts like a liquid acts on Earth.
	the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).

Question 53 (1 point)

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The Sun's visible surface (that is, the surface we can see with our eyes) is called the

Question 53 options:

	core.
	chromosphere.
	corona.
	photosphere.

Question 54 (1 point)

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What is the solar wind?

Question 54 options:

	the wind that causes huge arcs of gas to rise above the Sun's surface
	the strong wind that blows sunspots around on the surface of the Sun
	a stream of charged particles flowing outward from the surface of the Sun
	the uppermost layer of the Sun, which lies just above the corona

Question 55 (1 point)

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If star A is closer to us than star B, then Star A's parallax angle is

Question 55 options:

	larger than that of Star B.
	smaller than that of Star B.
	fewer parsecs than that of Star B.
	hotter than that of Star B.

Question 56 (1 point)

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Astronomers can measure a star's mass in only certain cases. Which one of the following cases might allow astronomers to measure a star's mass?

Question 56 options:

	The star is of spectral type G.
	The star is a member of a binary star system.
	The star is of spectral type A.
	We know the star's luminosity and distance.

Question 57 (1 point)

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On an H-R diagram, stellar radii

Question 57 options:

	are impossible to determine.
	decrease from left to right.
	increase diagonally from the lower left to the upper right.
	are greatest in the lower left and least in the upper right.

Question 58 (1 point)

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What is a white dwarf?

Question 58 options:

	It is a type of star that produces energy by gravitational contraction.
	It is a main sequence star of spectral type F, which tends to look white in color.
	It is a star that follows a period-luminosity relation.
	It is the remains of a star that ran out of fuel for nuclear fusion.

Question 59 (1 point)

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Interstellar dust consists mostly of

Question 59 options:

	hydrogen and helium atoms.
	microscopic particles of carbon and silicon.
	ozone "smog."
	the same tiny particles found in household dust.
	tiny grains of water ice.

Question 60 (1 point)

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Most interstellar clouds remain stable in size because the force of gravity is opposed by ________ within the cloud.

Question 60 options:

	thermal pressure
	stellar winds
	degeneracy pressure
	radiation pressure

Question 61 (1 point)

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What kind of gas cloud is most likely to give birth to stars?

Question 61 options:

	a cold, low-density gas cloud
	a hot, low-density gas cloud
	a hot, dense gas cloud
	a cold, dense gas cloud

Question 62 (1 point)

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Which of the following statements about the first stars that were born in the universe is expected to be true?

Question 62 options:

	They were probably orbited only by terrestrial planets but no jovian planets.
	They were made only from hydrogen and helium.
	They were made from pure energy.
	They were made approximately of 98% hydrogen and helium and 2% of heavier elements.

Question 63 (1 point)

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When does a protostar become a main-sequence star?

Question 63 options:

	at the instant that the first hydrogen fusion reactions occur in the protostar's core
	when it becomes luminous enough to emit thermal radiation
	when a piece of a molecular cloud first begins to contract into a star
	when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space

Question 64 (1 point)

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Which of the following stars will live longest?

Question 64 options:

	4 solar-mass star
	2 solar-mass star
	3 solar-mass star
	1 solar-mass star

Question 65 (1 point)

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What is a helium flash?

Question 65 options:

	It is a sudden brightening of a low-mass star, detectable from Earth by observing spectral lines of helium.
	It is another name for the helium fusion reaction.
	It is the sudden onset of helium fusion in the core of a low-mass star.
	It is the ignition of helium shell fusion in a high-mass star with a carbon core.

Question 66 (1 point)

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What is a planetary nebula?

Question 66 options:

	the remains of a high-mass star that has exploded
	gas created from the remains of planets that once orbited a dead star
	interstellar gas from which planets are likely to form in the not-too-distant future
	gas ejected from a low-mass star in the final stage of its life

Question 67 (1 point)

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How are low-mass red giant stars important to our existence?

Question 67 options:

	These stars provide most of the light that reaches us from globular clusters.
	These stars manufactured most of the carbon atoms in our bodies.
	These stars manufactured virtually all the elements out of which we and our planet are made.
	These stars generate the energy that makes life on Earth possible.

Question 68 (1 point)

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A typical white dwarf is

Question 68 options:

	about the same size and mass as the Sun but much hotter.
	as massive as the Sun but only about as large in size as Jupiter.
	as massive as the Sun but only about as large in size as Earth.
	as large in diameter as the Sun but only about as massive as Earth.

Question 69 (1 point)

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What is an accretion disk?

Question 69 options:

	a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole
	a disk of material found around every white dwarf in the Milky Way Galaxy
	any flattened disk in space, such as the disk of the Milky Way Galaxy
	a stream of gas flowing from one star to its binary companion star

Question 70 (1 point)

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A neutron star is

Question 70 options:

	the remains of a star that died by expelling its outer layers in a planetary nebula.
	the remains of a star that died in a massive star supernova (if no black hole was created).
	an object that will ultimately become a black hole.
	a star made mostly of elements with high atomic mass numbers, so that they have lots of neutrons.

Question 71 (1 point)

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A neutron star is

Question 71 options:

	the remains of a star that died in a massive star supernova (if no black hole was created).
	an object that will ultimately become a black hole.
	the remains of a star that died by expelling its outer layers in a planetary nebula.
	a star made mostly of elements with high atomic mass numbers, so that they have lots of neutrons.

Question 72 (1 point)

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Which of the following are typically found in the halo of our galaxy?

Question 72 options:

	stars of spectral types O and B
	cold gas and dust
	globular star clusters
	all of the above
	open star clusters

Question 73 (1 point)

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Which of the following represent the oldest stars of the Milky Way?

Question 73 options:

	Cepheid variable stars
	O stars
	stars in globular clusters
	red giant stars in spiral arms
	the Sun and other stars with similar mass

Question 74 (1 point)

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Why can't we see the center of our galaxy with our eyes?

Question 74 options:

	Interstellar dust and gas absorbs and scatters visible light before it can reach us from the center.
	Stars are too densely spaced in the plane of our galaxy to see all the way to the center.
	We are in the center of the Milky Way.
	There are no stars in the center of the Milky Way, just a supermassive black hole.
	The center of the Milky Way does not emit enough visible light.

Question 75 (1 point)

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Which of the following best describes the orbits of stars in the halo?

Question 75 options:

	Some halo stars orbit around the galactic center but others never pass through the plane of the galactic disk.
	Halo stars have elliptical orbits, with random orientations.
	Halo stars have orbits confined to a relatively thin plane.
	Halo stars have elliptical orbits, but all orbiting in the same direction.
	Halo stars orbit the centers of their globular clusters, but do not orbit the center of the galaxy.

Question 76 (1 point)

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Which types of galaxies have a halo component?

Question 76 options:

	ellipticals only
	spirals only
	irregulars only
	both spirals and ellipticals

Question 77 (1 point)

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White dwarf supernovae are good standard candles for distance measurements because

Question 77 options:

	all white dwarf supernovae occurred at about the same time in the history of the universe.
	all white dwarf supernovae have about the same peak luminosity.
	white dwarf supernovae occur only among very massive stars.
	all white dwarf supernovae start out bright and fade with time.
	all galaxies have at least one white dwarf supernova each year.

Question 78 (1 point)

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Which of the following expresses the major idea of Hubble's Law?

Question 78 options:

	More distant galaxies appear younger.
	The closer a galaxy is to us, the faster it moves away from us.
	All galaxies are moving away from us equally fast.
	There must have been a Big Bang.
	The more distant a galaxy is from us, the faster it moves away from us.

Question 79 (1 point)

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In what sense do telescopes function as "time machines"?

Question 79 options:

	They allow us to observe individual stars and galaxies as they change with time.
	Some of the oldest telescopes are still in use today.
	They allow us to see the Milky Way Galaxy as it was when it was much younger.
	They allow us to see distant objects as they were in the distant past.

Question 80 (1 point)

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What is a central dominant galaxy?

Question 80 options:

	a hypothesized galaxy type that no longer exists, but once dominated the structure of the universe
	a spiral galaxy from which many smaller galaxies form when it is stripped apart by tidal forces
	a giant spiral galaxy that exerts large tidal forces on other nearby galaxies
	a giant galaxy with several bright clumps of stars at the center of a dense cluster
	a galaxy around which many other smaller galaxies orbit