A Quiz On Astronomy For Pros

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A Quiz On Astronomy For Pros

Have you always wanted to follow a professional career in astronomy? If so, you can test out how qualified you are to go into the field by taking the challenging quiz below that only true professionals can pass with ease. Believe in yourself and tackle it. All the best and enjoy!


Questions and Answers
  • 1. 
    • A. 

      Planets are smaller than stars.

    • B. 

      All planets are made of rock and all stars are made of gas.

    • C. 

      Planets orbit stars, while stars orbit the center of the galaxy.

    • D. 

      Planets are dimmer than stars.

  • 2. 
    • A. 

      The Sun and several nearby stars, as well as the planets and other objects that orbit these stars

    • B. 

      A few hundred billion stars, bound together by gravity

    • C. 

      The Sun and the nine planets, and nothing else

    • D. 

      The Sun and all the objects that orbit it

  • 3. 
    • A. 

      System consisting of one or a few stars orbited by planets, moons, and smaller objects

    • B. 

      Collection of a few hundred million to a trillion or more stars, bound together by gravity

    • C. 

      Relatively small, icy object orbiting a star

    • D. 

      Nearby object orbiting a planet

    • E. 

      Large, glowing ball of gas powered by nuclear energy

  • 4. 
    • A. 

      The universe is another name for our Milky Way Galaxy.

    • B. 

      All the galaxies in all the superclusters

    • C. 

      A vast collection of stars that number as many as the grains of sand on all the beaches on Earth

    • D. 

      The sum total of all matter and energy

  • 5. 
    • A. 

      The event that marked the beginning of the expansion of the universe

    • B. 

      The explosion of a massive star at the end of its life

    • C. 

      The event that marked the birth of our solar system

    • D. 

      A gigantic explosion that blew all the galaxies in the universe to smithereens

  • 6. 
    • A. 

      Everything in the universe is gradually growing in size.

    • B. 

      The statement is not meant to be literal; rather, it means that our knowledge of the universe is growing.

    • C. 

      Average distances are increasing between star systems within galaxies.

    • D. 

      Average distances between galaxies are increasing.

  • 7. 
    Based on observations of the universal expansion, the age of the universe is about _________.
    • A. 

      14,000 years

    • B. 

      14 trillion years

    • C. 

      14 billion years

    • D. 

      14 million years

  • 8. 
    A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
    • A. 

      It uses "light-years" to talk about time, but a light-year is a unit of distance

    • B. 

      Light-years can only be used to talk about light

    • C. 

      A light-year is an astronomically large unit, so a product could not possibly be so advanced

    • D. 

      It doesn't specify the number of light-years

  • 9. 
    The term observable universe refers to _________.
    • A. 

      That portion of the universe that we have so far photographed through telescopes

    • B. 

      That portion of the universe that we can see in principle, given the finite age of the universe

    • C. 

      The portion of the universe that is not hidden from view by, for example, being below the horizon

    • D. 

      The portion of the universe that can be seen by the naked eye

  • 10. 
    On a scale in which the distance from the Sun to the Earth is about 15 meters, the distance from the Earth to the Moon is _________.
    • A. 

      About 30 meters

    • B. 

      Small enough to fit within your hand

    • C. 

      About 1 meter

    • D. 

      About 5 meters

  • 11. 
    • A. 

      About the distance across the United States

    • B. 

      About the distance across 50 football fields

    • C. 

      About the distance across the state of Delaware

    • D. 

      100 meters

  • 12. 
    The number of stars in the Milky Way Galaxy is approximately _________.
    • A. 

      A few hundred billion

    • B. 

      A few hundred

    • C. 

      A few hundred million

    • D. 

      A few hundred thousand

  • 13. 
    An astronomical unit (AU) is _________.
    • A. 

      The average distance between any two planets

    • B. 

      The average distance between the Sun and Pluto

    • C. 

      The average distance between the Sun and Earth

    • D. 

      Any very large unit, such as a light-year

  • 14. 
    • A. 

      The plane of the Milky Way Galaxy

    • B. 

      The plane of the Earth's orbit around the Sun

    • C. 

      The plane of the Sun's equator

    • D. 

      The plane of the Earth's equator

  • 15. 
    • A. 

      One month

    • B. 

      One week

    • C. 

      The time varies significantly depending on the orbit.

    • D. 

      One day

    • E. 

      One year

  • 16. 
    Which of the following has your "cosmic address" in the correct order? [Hint]
    • A. 

      You, Earth, Local Group, Local Supercluster, solar system, Milky Way Galaxy, universe

    • B. 

      You, Earth, solar system, Local Group, Local Supercluster, Milky Way Galaxy, universe

    • C. 

      You, Earth, solar system, Local Group, Milky Way Galaxy, Local Supercluster, universe

    • D. 

      You, Earth, Milky Way Galaxy, solar system, Local Group, Local Supercluster, universe

    • E. 

      You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe

  • 17. 
    Using the ideas discussed in the text, in what sense are we "star stuff"? [Hint]
    • A. 

      Movie stars and other people are all made of the same stuff, so we all have the potential to be famous.

    • B. 

      Our overall chemical composition is about the same as that of stars.

    • C. 

      Nearly every atom from which we are made was once inside of a star.

    • D. 

      We could not survive without light from our star, the Sun.

  • 18. 
    • A. 

      Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.

    • B. 

      Without galaxies, the universe could not be expanding.

    • C. 

      Deep in their centers, galaxies created the elements from which we are made.

    • D. 

      Without galaxies, there could not have been a Big Bang.

  • 19. 
    When we look at an object that is 1,000 light-years away we see it _________. [Hint]
    • A. 

      As it was 1,000 years ago

    • B. 

      Looking just the same as our ancestors would have seen it 1,000 years ago

    • C. 

      As it is right now, but it appears 1,000 times dimmer

    • D. 

      As it was 1,000 light-years ago

  • 20. 
    • A. 

      Galaxy 2 must be twice as old as Galaxy 1

    • B. 

      Galaxy 1 must be twice as big as Galaxy 2

    • C. 

      We are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2

    • D. 

      We are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2

  • 21. 
    Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like? [Hint]
    • A. 

      They are all much smaller than the Sun and are spread out evenly over a distance about the length of a large classroom.

    • B. 

      They are all much smaller than the Sun. Six planets are located within a few centimeters of the Sun, and three planets are located at distances ranging up to about a meter.

    • C. 

      They are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the remaining planets are spread much farther apart, with Pluto more than a half a kilometer from the Sun.

    • D. 

      The planets range in size from about the size of a marble to the size of a baseball. They are spread out over a region about the size of a football field.

  • 22. 
    • A. 

      Several years

    • B. 

      Several thousand years

    • C. 

      Several days

    • D. 

      Several weeks

  • 23. 
    The total number of stars in the observable universe is about _________. [Hint]
    • A. 

      The same as the number of grains of sand in a large sandbox

    • B. 

      The same as the number of atoms that make up the Earth

    • C. 

      100 billion

    • D. 

      The same as the number of grains of sand on all the beaches on Earth

  • 24. 
    • A. 

      Roughly halfway between the center and the edge of the visible disk of the galaxy

    • B. 

      In the halo of the galaxy

    • C. 

      At the far edge of the galaxy's visible disk

    • D. 

      Very near the center of the galaxy

  • 25. 
    If we imagine the history of the universe compressed into one year, the dinosaurs became extinct _________. [Hint]
    • A. 

      About an hour ago

    • B. 

      About 6 months ago

    • C. 

      Yesterday

    • D. 

      About 3 weeks ago

  • 26. 
    Relative to the age of the universe, how old is our solar system? [Hint]
    • A. 

      It is between about one-quarter and one-half the age of the universe

    • B. 

      It is about 1% as old as the universe.

    • C. 

      It is about the same age as the universe because it formed shortly after the Big Bang.

    • D. 

      It is between about 5% and 10% as old as the universe.

  • 27. 
    How do the speeds at which we are moving with the Earth's rotation and orbit compare to the speeds of more familiar objects? [Hint]
    • A. 

      The Earth's rotation is carrying most people around the axis faster than a commercial jet travels, and the Earth's orbit is carrying us around the Sun faster than the Space Shuttle orbits the Earth.

    • B. 

      The Earth's rotation is carrying most people around the axis faster than a commercial jet travels, and the Earth's orbit is carrying us around the Sun faster than the Space Shuttle orbits the Earth.

    • C. 

      The Earth's rotation is carrying most people around the axis at about the speed at which the Space Shuttle orbits the Earth, and the Earth's orbit is carrying us around the Sun at nearly the speed of light.

    • D. 

      The Earth's rotation is carrying most people around the axis at about the speed of a commercial jet, and the Earth's orbit is carrying us around the Sun at about the speed of a military jet.

  • 28. 
    Why do the patterns of the stars in our sky look the same from year to year? [Hint]
    • A. 

      Although these stars move quite fast by human standards, they are so far away that it would take thousands of years for their motion to be noticeable to the eye.

    • B. 

      Because these stars are not moving.

    • C. 

      Because although these stars move quite fast as they orbit around the Milky Way Galaxy, they all move together so they don't change their relative positions.

    • D. 

      Because although these stars are moving, they move so slowly --- typically about the speed of a snail --- that their motion is not noticeable.

  • 29. 
    Astronomers infer that the universe is expanding because distant galaxies all appear to _________. [Hint]
    • A. 

      Be moving away from us, with more distant ones moving faster

    • B. 

      Be growing in size

    • C. 

      Be made of dark matter

    • D. 

      Rotate rapidly

  • 30. 
    • A. 

      Except for a few nearby galaxies, all other galaxies are moving away from us.

    • B. 

      Some stars are moving closer to us and others are moving farther away from us.

    • C. 

      The mysterious dark matter is the fastest-moving material in the universe.

    • D. 

      Your speed of rotation around Earth's axis is faster if you live near the equator than if you live near the North Pole.

  • 31. 
    About how many stars are visible to the naked eye on a clear, dark night away from city lights? [Hint]
    • A. 

      A couple thousand

    • B. 

      A few dozen

    • C. 

      A few hundred billion

    • D. 

      Several million

  • 32. 
    • A. 

      A constellation is a group of stars that are all located in about the same place in space.

    • B. 

      A constellation is a group of stars related through an ancient story.

    • C. 

      A constellation is a region in the sky as seen from Earth.

    • D. 

      A constellation is any random grouping of stars in the sky.

  • 33. 
    • A. 

      The path the Sun appears to trace around the celestial sphere each year

    • B. 

      The path on the Earth traced by the Moon's shadow during a solar eclipse

    • C. 

      The Sun's daily path from east to west in our sky

    • D. 

      A half-circle extending from your horizon due north, through your zenith, to your horizon due south

  • 34. 
    • A. 

      The celestial sphere is a model that shows the true locations of the Sun and a few thousand of the nearest stars.

    • B. 

      It is a model of how the stars are arranged in the sky relative to our Sun, which is in the middle of the sphere.

    • C. 

      It represents a belief in an Earth-centered universe, and hence is no longer considered to have any use.

    • D. 

      The celestial sphere is a representation of how the sky looks as seen from Earth.

  • 35. 
    • A. 

      We mean the bright stars of the constellations that lie along the ecliptic in our sky.

    • B. 

      We mean the patchy band of light that represents what we see when we look into the plane of the Milky Way Galaxy.

    • C. 

      We mean the whitish patch of light we see when we look toward the center of the Milky Way Galaxy.

    • D. 

      We mean the spiral-shaped galaxy that we can see when we look in the right direction in our sky.

  • 36. 
    • A. 

      The angular distance between those two bright stars in the sky is about 2 meters.

    • B. 

      The angular size of the Sun is about the same as that of the Moon.

    • C. 

      You can use your outstretched hand against the sky to estimate angular sizes and angular distances.

    • D. 

      The angular distance between those two houses in the distance is 30 degrees.

  • 37. 
    Which of the following correctly describes the meridian in your sky? [Hint]
    • A. 

      A half-circle extending from your horizon due east, through the north celestial pole, to your horizon due west

    • B. 

      A half-circle extending from your horizon due north, through your zenith, to your horizon due south

    • C. 

      The point directly over your head

    • D. 

      A half-circle extending from your horizon due east, through your zenith, to your horizon due west

  • 38. 
    The point directly over your head is called _________. [Hint]
    • A. 

      The North Star

    • B. 

      The zenith

    • C. 

      The meridian

    • D. 

      The celestial pole

  • 39. 
    Stars that are visible in the sky on any clear night of the year, at any time of the night, are called _________. [Hint]
    • A. 

      Seasonal

    • B. 

      Circumpolar

    • C. 

      Bright

    • D. 

      Celestial

  • 40. 
    We describe a location on the Earth's surface by stating its _________. [Hint]
    • A. 

      Altitude and direction (or azimuth)

    • B. 

      Latitude and longitude

    • C. 

      Latitude and direction

    • D. 

      Meridian and longitude

  • 41. 
    Which of the following correctly describes a relationship between the sky and your location on Earth? [Hint]
    • A. 

      If you are in the Northern Hemisphere, the altitude of the north celestial pole equals your latitude.

    • B. 

      If you are in the Northern Hemisphere, the longitude of the north celestial pole is circumpolar, and therefore crosses your zenith at the meridian.

    • C. 

      If you are in the Northern Hemisphere, the altitude of the celestial equator equals your latitude.

    • D. 

      If you are in the Northern Hemisphere, the altitude of the north celestial pole equals your longitude.

  • 42. 
    Which of the following best describes why we have seasons on Earth? [Hint]
    • A. 

      The varying speed of the Earth in its orbit around the Sun gives us summer when we are moving fastest and winter when we are moving slowest.

    • B. 

      The varying speed of the Earth in its orbit around the Sun gives us summer when we are moving fastest and winter when we are moving slowest.

    • C. 

      The tilt of the Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

    • D. 

      The varying speed of the Earth in its orbit around the Sun gives us summer when we are moving fastest and winter when we are moving slowest.

  • 43. 
    Each part below describes how a few astronomical phenomena are related to time periods. Which list is correct? (Careful: some lists are partially correct.)
    • A. 

      The Earth's rotation defines a day. The cycle of the Moon's phases takes about a month. The Earth's orbit defines a year. The Earth's cycle of axis precession takes 26,000 years.

    • B. 

      The Earth's rotation defines a day. The saros cycle of eclipses defines a month. The Earth's orbit defines a year. The Earth's cycle of axis precession takes 26,000 years.

    • C. 

      The Earth's rotation defines a day. The Sun's rotation defines a week. The Moon's rotation defines a month. The Earth's orbit defines a year.

    • D. 

      The Earth's rotation defines a day. The cycle of the Moon's phases takes about a week. The Earth's orbit defines a year. The Earth's cycle of axis precession defines a month.

  • 44. 
    If we have a new moon today, when we will have the next full moon? [Hint]
    • A. 

      In about a month

    • B. 

      In about 1 week

    • C. 

      In about 2 weeks

    • D. 

      In about 6 months

  • 45. 
    We cannot see a new moon in our sky because _________. [Hint]
    • A. 

      It is above the horizon during the daytime

    • B. 

      No sunlight is illuminating the Moon

    • C. 

      A new moon is quite near the Sun in the sky

    • D. 

      It is obscured by the Earth's shadow

  • 46. 
    Lunar eclipses can occur only during a _________. [Hint]
    • A. 

      Full moon

    • B. 

      First quarter moon

    • C. 

      Third quarter moon

    • D. 

      New moon

  • 47. 
    • A. 

      The annual cycle of the seasons

    • B. 

      The roughly one-month cycle of lunar phases in the sky

    • C. 

      The 26,000-year cycle of the Earth's precession

    • D. 

      The roughly 18-year cycle over which the pattern of eclipses repeats

  • 48. 
    While a planet is experiencing apparent retrograde motion (as seen from Earth), _________. [Hint]
    • A. 

      It moves backwards (clockwise as viewed from far above the Earth's north pole) in its orbit of the Sun

    • B. 

      The planet is getting closer to the Sun in its orbit

    • C. 

      The planet moves westward relative to the stars, rather than the usual eastward relative to the stars

    • D. 

      The planet is getting closer to the Sun in its orbit

  • 49. 
    Which of the following statements about the celestial sphere is NOT true? [Hint]
    • A. 

      The "celestial sphere" is just another name for our universe.

    • B. 

      When we look in the sky, the stars all appear to be located on the celestial sphere.

    • C. 

      The celestial sphere does not exist physically.

    • D. 

      The Earth is placed at the center of the celestial sphere.

  • 50. 
    An angle of 1 arcsecond is _________. [Hint]
    • A. 

      Less than the thickness of a hair held at arm's length

    • B. 

      About the width of your fist held at arm's length

    • C. 

      About the width of a finger held at arm's length

    • D. 

      Slightly more than the width of a basketball held at arm's length

  • 51. 
    When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________. [Hint]
    • A. 

      Higher in the sky

    • B. 

      Brighter

    • C. 

      Dimmer

    • D. 

      Lower in the sky

  • 52. 
    Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________. [Hint]
    • A. 

      Latitude 40 degrees south

    • B. 

      Latitude 40 degrees north

    • C. 

      Latitude 50 degrees south

    • D. 

      Longitude 40 degrees

  • 53. 
    • A. 

      To the right of Polaris; that is, 90 degrees counterclockwise from its current position

    • B. 

      To the left of Polaris; that is, 90 degrees clockwise from its current position

    • C. 

      Directly above Polaris

    • D. 

      Still in the same place, below Polaris

  • 54. 
    In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________. [Hint]
    • A. 

      Our evening view of space depends on where the Earth is located in its orbit around the Sun

    • B. 

      On any particular night, we can only see stars that are directly opposite (180 degrees away from) the Sun in the sky

    • C. 

      Some constellations are circumpolar

    • D. 

      During some times of year, some constellations drop below the southern horizon

  • 55. 
    The Sun's path, as viewed from the equator, is highest on _________. [Hint]
    • A. 

      The day when Earth is closest to the Sun

    • B. 

      The spring and fall equinoxes

    • C. 

      The winter solstice

    • D. 

      The summer solstice

  • 56. 
    • A. 

      The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.

    • B. 

      The region of the Earth where the Sun never rises on the summer solstice would be larger (extending farther south) than it is now.

    • C. 

      Polaris would not be our North star.

    • D. 

      Summers and winters would be more severe (for example, hotter and colder, respectively) than they are now.

  • 57. 
    If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________. [Hint]
    • A. 

      The four seasons would each be twice as long as they are now

    • B. 

      The cycle of precession would take 13,000 years instead of 26,000 years

    • C. 

      The Earth would not have seasons

    • D. 

      Stars would take twice as long to rise and set

  • 58. 
    • A. 

      It is responsible for the fact that the seasons are opposite in the Northern and Southern hemispheres.

    • B. 

      It doesn't --- Earth's orbital distance plays no obvious role in the seasons.

    • C. 

      It makes summer warmer in the Northern Hemisphere than in the Southern Hemisphere.

    • D. 

      It causes the seasons to be more extreme than they would be if the Earth's distance from the Sun were always the same.

  • 59. 
    • A. 

      Your friend will see a gibbous moon.

    • B. 

      Your friend will also see a crescent moon.

    • C. 

      Your friend will see a first quarter moon.

    • D. 

      Your friend won't see the Moon tonight, because it is up only in the morning.

  • 60. 
    Suppose it is full moon. What phase of the Earth would someone on the Moon see at this time? [Hint]
    • A. 

      The Earth does not go through phases as seen from the Moon.

    • B. 

      New Earth

    • C. 

      First quarter Earth

    • D. 

      Full Earth

  • 61. 
    It's 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase? [Hint]
    • A. 

      Full

    • B. 

      First quarter

    • C. 

      New

    • D. 

      Third quarter

  • 62. 
    You observe a full moon rising at sunset. What will you see 6 hours later? [Hint]
    • A. 

      A waning gibbous moon

    • B. 

      A waning gibbous moon

    • C. 

      A full moon on or near your meridian

    • D. 

      A third quarter moon

  • 63. 
    • A. 

      The Moon goes through a complete cycle of phases about every 29 1/2 days.

    • B. 

      The nodes of the moon's orbit precess with an 18-year period.

    • C. 

      The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.

    • D. 

      The Moon is only about 1/4 as large as Earth in diameter.

  • 64. 
    For most of history, the lack of observable stellar parallax was interpreted to mean that _________. [Hint]
    • A. 

      The Earth is stationary at the center of the universe

    • B. 

      Stars were too far away for parallax to be measured with available technology

    • C. 

      Galileo's theories of the universe were essentially correct

    • D. 

      Stars must all lie at the same distance from Earth, on the celestial sphere

  • 65. 
    During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space? [Hint]
    • A. 

      The Earth and Mars are getting closer together.

    • B. 

      Earth is catching up with and passing by Mars in their respective orbits.

    • C. 

      Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun.

    • D. 

      Earth and Mars are on opposite sides of the Sun.

  • 66. 
    Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by _________. [Hint]
    • A. 

      The Arecibo radio telescope in Puerto Rico

    • B. 

      The Keck telescope on Mauna Kea, Hawaii

    • C. 

      The Hubble Space Telescope (which orbits Earth)

    • D. 

      The Galileo spacecraft, when it was orbiting Jupiter

  • 67. 
    • A. 

      It helped them keep track of time and seasons, and it was used by some cultures for navigation.

    • B. 

      It allowed them to predict eclipses with great accuracy.

    • C. 

      It helped them understand our cosmic origins.

    • D. 

      It helped them find uses for ancient structures like Stonehenge.

  • 68. 
    Scientific thinking is _________. [Hint]
    • A. 

      An ancient mode of thinking first invented in Egypt

    • B. 

      Completely different from any other type of thinking

    • C. 

      Based on everyday ideas of observation and trial-and-error experiments

    • D. 

      A difficult process that only a handful of people can do well

  • 69. 
    The names of the seven days of the week are based on _________. [Hint]
    • A. 

      The seven naked-eye objects that appear to move among the constellations

    • B. 

      The names of prophets in the Bible

    • C. 

      The seven most prominent constellations in the summer sky

    • D. 

      The names of the seven planets closest to the Sun

  • 70. 
    Ptolemy was important in the history of astronomy because he _________. [Hint]
    • A. 

      Was the first to create a model of the solar system that placed the Sun rather than the Earth at the center

    • B. 

      Was the first to believe that all orbits are perfect circles

    • C. 

      Developed the first scientific model of the universe

    • D. 

      Developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries

  • 71. 
    The ancient Greeks get a lot of attention for their contributions to science because _________. [Hint]
    • A. 

      They were the first people known to try to explain nature with models based on reason, mathematics, and geometry, without resort to the supernatural

    • B. 

      They were the first people to realize that Earth is a planet orbiting the Sun

    • C. 

      They were the only ancient culture that kept written records of their astronomical observations

    • D. 

      The books of every other culture were lost in the destruction of the library of Alexandria

  • 72. 
    • A. 

      A model designed to explain what we see in the sky while having the Earth located in the center of the universe.

    • B. 

      It is the name given to sphere-shaped models that show all the constellations as they appear in our sky on the celestial sphere.

    • C. 

      A model designed to explain what we see in the sky while having the Earth orbit the Sun.

    • D. 

      A model of the Milky Way Galaxy that has our solar system located at its center.

  • 73. 
    • A. 

      A Sun-centered model of planetary motion described by Ptolemy

    • B. 

      An Earth-centered model of planetary motion described by Ptolemy

    • C. 

      The Earth-centered model of the cosmos in which the Earth was surrounded by seven perfect spheres, one each for the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn

    • D. 

      The first scientific model to successfully predict solar and lunar eclipses

  • 74. 
    The great contribution of Nicholas Copernicus was to _________. [Hint]
    • A. 

      Prove that the Earth is not the center of the universe

    • B. 

      Discover the law of gravity

    • C. 

      Create a detailed model of our solar system with the Sun rather than Earth at the center

    • D. 

      Discover the laws of planetary motion

  • 75. 
    The great contribution of Tycho Brahe was to _________. [Hint]
    • A. 

      Discover four moons orbiting Jupiter, thereby lending strong support to the idea that the Earth is not the center of the universe

    • B. 

      Observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion

    • C. 

      Discover that planets orbit the Sun in elliptical orbits with varying speed

    • D. 

      Offer the first detailed model of a Sun-centered solar system, thereby beginning the process of overturning the Earth-centered model of the Greeks

  • 76. 
    Which of the following was NOT observed by Galileo? [Hint]
    • A. 

      Phases of Venus.

    • B. 

      Mountains and valleys on the Moon

    • C. 

      Stellar parallax

    • D. 

      Four moons orbiting Jupiter

  • 77. 
    Which of the following statements about an ellipse is NOT true? [Hint]
    • A. 

      The focus of an ellipse is always located precisely at the center of the ellipse.

    • B. 

      The semimajor axis of an ellipse is half the length of the longest line that you can draw across an ellipse.

    • C. 

      An ellipse with a large eccentricity looks much more elongated (stretched out) than an ellipse with a small eccentricity.

    • D. 

      A circle is considered to be a special type of ellipse.

  • 78. 
    Which of the following is not one of, nor a direct consequence of, Kepler's Laws? [Hint]
    • A. 

      More distant planets orbit the Sun at slower speeds.

    • B. 

      The orbit of each planet about the Sun is an ellipse with the Sun at one focus.

    • C. 

      The force of attraction between any two objects decreases with the square of the distance between their centers.

    • D. 

      As a planet moves around its orbit, it sweeps out equal areas in equal times.

    • E. 

      A planet or comet in a noncircular orbit travels faster when it is nearer to the Sun and slower when it is farther from the Sun.

  • 79. 
    Scientific models are used to _________. [Hint]
    • A. 

      Prove that past paradigms no longer hold true

    • B. 

      Make specific predictions that can be tested through observations or experiments

    • C. 

      Present the solar system to the general public

    • D. 

      Make miniature representations of the universe

  • 80. 
    In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called _________. [Hint]
    • A. 

      A theory

    • B. 

      A hypothesis

    • C. 

      A paradigm

    • D. 

      A Ptolemaic model

  • 81. 
    • A. 

      A week would have eight days instead of seven.

    • B. 

      Its brightness would make it possible to read by starlight at night.

    • C. 

      Its slow motion through the sky would have led it to be named after the Goddess of Procrastination.

    • D. 

      Its gravity would cause the tides to be much higher than they actually are.

    • E. 

      The discovery that the Earth is a planet going around the Sun would have come hundreds of years earlier.

  • 82. 
    How does a 12-month lunar calendar differ from our 12-month solar calendar? [Hint]
    • A. 

      Its new year always occurs in February instead of on January 1.

    • B. 

      It uses a 23-hour rather than a 24-hour day.

    • C. 

      It has about 11 fewer days.

    • D. 

      It does not have seasons.

  • 83. 
    • A. 

      They were all places used for religious sacrifice.

    • B. 

      They all can be used as lunar calendars.

    • C. 

      They were all used by ancient peoples for astronomical observations.

    • D. 

      They were all built on the orders of ancient kings.

  • 84. 
    • A. 

      It held that the planets moved along small circles that moved on larger circles around the Earth, and that the combined motion sometimes resulted in backward motion.

    • B. 

      It held that sometimes the planets moved backwards along their circular orbits.

    • C. 

      It held that this motion occurs as Earth passes by another planet in its orbit of the Sun.

    • D. 

      It held that the planets resided on giant spheres that sometimes turned clockwise and sometimes turned counterclockwise.

  • 85. 
    • A. 

      Copernicus placed the Sun at the center, but did not realize that the Moon orbits the Earth.

    • B. 

      Copernicus used perfect circles for the orbits of the planets.

    • C. 

      Copernicus misjudged the distances between the planets.

    • D. 

      Copernicus placed the planets in the wrong order going outward from the Sun.

  • 86. 
    Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit? [Hint]
    • A. 

      Winter

    • B. 

      Spring

    • C. 

      Fall

    • D. 

      Summer

  • 87. 
    • A. 

      More massive planets must have more circular orbits.

    • B. 

      A planet's mass has no effect on its orbit around the Sun.

    • C. 

      A more massive planet must have a larger semimajor axis.

    • D. 

      More massive planets orbit the Sun at higher average speed.

  • 88. 
    All the following statements are true. Which one follows directly from Kepler's third law (p2 = a3)? [Hint]
    • A. 

      Venus orbits the Sun at a slower average speed than Mercury.

    • B. 

      Venus takes longer to rotate than it does to orbit the Sun.

    • C. 

      Venus is more massive than Mercury.

    • D. 

      Venus has a thicker atmosphere than Mercury.

  • 89. 
    Galileo challenged the idea that objects in the heavens were perfect by _________. [Hint]
    • A. 

      Inventing the telescope

    • B. 

      Showing that heavy objects fall at the same rate as lighter objects

    • C. 

      Proving Kepler's laws were correct

    • D. 

      Observing sunspots on the Sun and mountains on the Moon

  • 90. 
    Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun? [Hint]
    • A. 

      Four moons of Jupiter.

    • B. 

      Patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face

    • C. 

      Phases of Venus

    • D. 

      The Milky Way is composed of many individual stars.

  • 91. 
    • A. 

      Science consists of proven theories that are understood to be true explanations of reality.

    • B. 

      Scientific explanations should be based solely on natural causes.

    • C. 

      A scientific model must make testable predictions.

    • D. 

      Science progresses through the creation and testing of models that explain observation as simply as possible.

  • 92. 
    Which of the following is NOT part of a good scientific theory? [Hint]
    • A. 

      A scientific theory must explain a wide variety of phenomena observed in the natural world.

    • B. 

      A scientific theory should be based on natural processes and should not invoke the supernatural or divine.

    • C. 

      A scientific theory cannot be accepted until it has been proven true beyond all doubt.

    • D. 

      A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise.

  • 93. 
    Only one of the statements below uses the term theory in its correct, scientific sense. Which one? [Hint]
    • A. 

      I have a new theory about the cause of earthquakes, and I plan to start testing it soon.

    • B. 

      I wrote a theory that is 152 pages long.

    • C. 

      Evolution is only a theory, so there's no reason to think it really happened.

    • D. 

      Einstein's theory of relativity has been tested and verified thousands of times.

  • 94. 
    Which of the following best describes how modern astronomers view astrology? [Hint]
    • A. 

      Astrology is a synonym for astronomy.

    • B. 

      Astrology is new age mumbo-jumbo that was a waste of time when it was invented thousands of years ago and remains a waste of time today.

    • C. 

      Astrology was a great idea until it was disproved by the work of Copernicus, Tycho, Kepler, and Galileo.

    • D. 

      Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.

  • 95. 
    The difference between speed and velocity is that _________. [Hint]
    • A. 

      Velocity also includes a direction

    • B. 

      Velocity is the same as acceleration whereas speed is different

    • C. 

      They are expressed in different units

    • D. 

      Velocity is calculated using a physics equation

  • 96. 
    The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds? [Hint]
    • A. 

      30 m/s2

    • B. 

      30 m/s

    • C. 

      20 m/s

    • D. 

      10 m/s2

    • E. 

      10 m/s

  • 97. 
    Momentum is defined as _________. [Hint]
    • A. 

      Force times velocity

    • B. 

      Mass times speed

    • C. 

      Mass times acceleration

    • D. 

      Mass times velocity

  • 98. 
    Suppose you lived on the Moon. Which of the following would be true? [Hint]
    • A. 

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

    • B. 

      Both your weight and your mass would be less than they are on Earth.

    • C. 

      Both your weight and your mass would be the same as they are on Earth.

    • D. 

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

  • 99. 
    In which of the following cases would you feel weightless? [Hint]
    • A. 

      While falling from a roof

    • B. 

      While walking on the Moon

    • C. 

      While accelerating downward in an elevator

    • D. 

      While parachuting from an airplane

  • 100. 
    Which of the following statements is NOT one of Newton's Laws of Motion? [Hint]
    • A. 

      For any force, there always is an equal and opposite reaction force.

    • B. 

      In the absence of a net force acting upon it, an object moves with constant velocity.

    • C. 

      The rate of change of momentum of an object is equal to the net force applied to the object.

    • D. 

      What goes up must come down.

  • 101. 
    Newton's Second Law of Motion tells us that the net force applied to an object equals its _________. [Hint]
    • A. 

      Mass times velocity

    • B. 

      Momentum times velocity

    • C. 

      Mass times acceleration

    • D. 

      Mass times energy

  • 102. 
    Suppose that two objects collide. Which of the following things is NOT the same both before and after the collision? [Hint]
    • A. 

      The total angular momentum of the objects

    • B. 

      The total temperature of the objects

    • C. 

      The total energy of the objects

    • D. 

      The total momentum of the objects

  • 103. 
    • A. 

      There exists an unbalanced reaction force

    • B. 

      There is less friction with the ice

    • C. 

      His angular momentum must be conserved, so reducing his radius must increase his speed of rotation

    • D. 

      There is less friction with the air

  • 104. 
    The energy attributed to an object by virtue of its motion is known as _________. [Hint]
    • A. 

      Radiative energy

    • B. 

      Kinetic energy

    • C. 

      Mass-energy

    • D. 

      Potential energy

  • 105. 
    Radiative energy is _________. [Hint]
    • A. 

      Energy from nuclear power plants

    • B. 

      Heat energy

    • C. 

      Energy of motion

    • D. 

      Energy carried by light

  • 106. 
    Absolute zero is _________. [Hint]
    • A. 

      100 degrees Celsius

    • B. 

      0 degrees Kelvin

    • C. 

      0 degrees Fahrenheit

    • D. 

      0 degrees Celsius

  • 107. 
    • A. 

      The average mass of particles in a substance

    • B. 

      The average kinetic energy of particles in a substance

    • C. 

      The total potential energy of particles in a substance

    • D. 

      The total amount of heat in a substance

  • 108. 
    In the formula E=mc2, what does E represent? [Hint]
    • A. 

      The radiative energy carried by light

    • B. 

      The kinetic energy of a moving object

    • C. 

      The electric field produced by a charge

    • D. 

      The gravitational potential energy of an object held above the ground

    • E. 

      The mass-energy, or potential energy stored in an object's mass

  • 109. 
    According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them _________. [Hint]
    • A. 

      Increases by a factor of 9

    • B. 

      Decreases by a factor of 9

    • C. 

      Decreases by a factor of 3

    • D. 

      Increases by a factor of 3

  • 110. 
    • A. 

      It allows us to calculate distances to distant objects.

    • B. 

      It explains why objects spin faster when they shrink in size.

    • C. 

      It can be used to determine the masses of many distant objects.

    • D. 

      It tells us that more-distant planets orbit the Sun more slowly.

  • 111. 
    • A. 

      Orbital energy is the amount of energy required for the object to leave orbit and escape into space.

    • B. 

      Orbital energy is a measure of the object's speed as it moves through its orbit.

    • C. 

      Orbital energy is the sum of the object's kinetic energy and its gravitational potential energy as it moves through its orbit.

    • D. 

      Orbital energy is the object's kinetic energy as it moves through its orbit.

  • 112. 
    Which statement must be true in order for a rocket to travel from Earth to another planet? [Hint]
    • A. 

      It must carry a lot of extra fuel.

    • B. 

      It must be launched from space, rather than from the ground.

    • C. 

      It must have very large engines.

    • D. 

      It must attain escape velocity from Earth.

  • 113. 
    Approximately where is it currently high tide on Earth? [Hint]
    • A. 

      Anywhere that ocean water laps upon the shore

    • B. 

      Only on the portion of the Earth facing directly toward the Moon

    • C. 

      On the portion of the Earth facing directly toward the Moon and on the portion of the Earth facing directly away from the Moon

    • D. 

      Wherever it is currently noon

  • 114. 
    Which of the following represents a case in which you are NOT accelerating? [Hint]
    • A. 

      Driving in a straight line at 60 miles per hour

    • B. 

      Driving 60 miles per hour around a curve

    • C. 

      Slamming on the brakes to come to a stop at a stop sign

    • D. 

      Going from 0 to 60 miles per hour in 10 seconds

  • 115. 
    Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen? [Hint]
    • A. 

      The 10-pound weight will hit the ground before the 5-pound weight.

    • B. 

      The 5-pound weight will hit the ground before the 10-pound weight.

    • C. 

      Both weights will float freely, since everything is weightless on the Moon.

    • D. 

      Both will hit the ground at the same time.

  • 116. 
    • A. 

      Because the Space Station is moving at constant velocity

    • B. 

      Because the Space Station is traveling so fast

    • C. 

      Because the Space Station is constantly in free-fall around the Earth

    • D. 

      Because there is no gravity in space

  • 117. 
    A net force acting on an object will always cause a change in the object's _________. [Hint]
    • A. 

      Momentum

    • B. 

      Direction

    • C. 

      Mass

    • D. 

      Speed

  • 118. 
    Suppose you are in an elevator that is traveling upward at constant speed. How does your weight compare to your normal weight on the ground? [Hint]
    • A. 

      You are weightless.

    • B. 

      It is greater.

    • C. 

      It is the same.

    • D. 

      It is less.

  • 119. 
    The planets never travel in a straight line as they orbit the Sun. According to Newton's second law of motion, this must mean that _________. [Hint]
    • A. 

      The planets will eventually fall into the Sun.

    • B. 

      The planets have angular momentum.

    • C. 

      A force is acting on the planets

    • D. 

      The planets are always accelerating.

  • 120. 
    • A. 

      This could never happen, because it is impossible for an object to shrink in size without an outside torque.

    • B. 

      The Sun's rate of rotation would slow.

    • C. 

      The Sun would rotate faster than it does now.

    • D. 

      The Sun's angular size in our sky would stay the same.

  • 121. 
    Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight? [Hint]
    • A. 

      The ball's gravitational potential energy is greatest at the instant when the ball is at its highest point.

    • B. 

      The ball's gravitational potential energy is always the same.

    • C. 

      The ball's gravitational potential energy is greatest at the instant the ball leaves your foot.

    • D. 

      The ball's gravitational potential energy is greatest at the instant it returns to hit the ground.

  • 122. 
    Suppose you heat up an oven to 400 degrees F and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven? [Hint]
    • A. 

      The oven has a higher temperature than the water.

    • B. 

      The water has a higher temperature than the oven.

    • C. 

      The molecules in the water are moving faster than the molecules in the oven.

    • D. 

      The water can transfer heat to your arm more quickly than the air.

  • 123. 
    Which of the following scenarios involves energy that we would typically calculate with Einstein's formula E=mc2? [Hint]
    • A. 

      An object accelerated to a great speed has a lot of kinetic energy.

    • B. 

      A mass raised to a great height has a lot of gravitational potential energy.

    • C. 

      When hydrogen is fused into helium, whether in the Sun or a nuclear bomb, some of the mass disappears and becomes energy.

    • D. 

      A burning piece of wood produces light and heat, therefore giving off radiative and thermal energy.

  • 124. 
    • A. 

      The energy goes to producing sound and to heating the ground, rock, and surrounding air.

    • B. 

      The rock keeps the energy inside it in the form of mass-energy.

    • C. 

      It is transformed back into gravitational potential energy.

    • D. 

      The energy goes into the ground, and as a result, the orbit of the Earth about the Sun is slightly changed.

  • 125. 
    Suppose that the Sun shrank in size but that its mass remained the same. What would happen to the orbit of the Earth? [Hint]
    • A. 

      Earth's orbit would be unaffected.

    • B. 

      Earth would change from a bound orbit to an unbound orbit and fly off into interstellar space.

    • C. 

      Earth's orbit would expand, and it would take more than one year to orbit the Sun.

    • D. 

      The size of Earth's orbit would shrink, and it would take less than one year to orbit the Sun.

  • 126. 
    • A. 

      An object on a bound orbit follows the same path around the Sun over and over, while an object on an unbound orbit approaches the Sun just once and then never returns.

    • B. 

      A bound orbit is an orbit allowed by the universal law of gravitation, and an unbound orbit is not.

    • C. 

      A bound orbit is circular, while an unbound orbit is elliptical.

    • D. 

      An object on a bound orbit has a gravitational attraction to the Sun, while an object on an unbound orbit does not.

  • 127. 
    Newton showed that Kepler's laws are _________. [Hint]
    • A. 

      Seriously in error

    • B. 

      The key to proving that the Earth orbits our Sun

    • C. 

      Natural consequences of the law of universal gravitation

    • D. 

      Actually only three of seven distinct laws of planetary motion

  • 128. 
    Each of the following lists two facts. Which pair of facts can be used with Newton's version of Kepler's third law to determine the mass of the Sun? [Hint]
    • A. 

      The Earth is 150 million km from the Sun and orbits the Sun in one year.

    • B. 

      The Earth rotates in one day and orbits the Sun in one year.

    • C. 

      The mass of the Earth is 6 ( 1024 kg and the Earth orbits the Sun in one year.

    • D. 

      Mercury is 0.387 AU from the Sun and Earth is 1 AU from the Sun.

  • 129. 
    • A. 

      Saturn must have lost a very tiny bit of its orbital energy.

    • B. 

      Saturn's rotation must have sped up slightly.

    • C. 

      Voyager 2 must have dipped through Saturn's atmosphere.

    • D. 

      Saturn must have captured an asteroid at precisely the moment that Voyager 2 passed by.

  • 130. 
    Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit that keeps it well above Jupiter's atmosphere and far from all of Jupiter's moons. Which of the following statements would be true? [Hint]
    • A. 

      Jupiter's gravity would suck in the asteroid, causing it to crash into Jupiter.

    • B. 

      Jupiter's gravity would capture the asteroid, making it a new moon of Jupiter.

    • C. 

      There is no way to predict what would happen.

    • D. 

      The asteroid's orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on.

  • 131. 
    Which of the following best describes the origin of ocean tides on Earth? [Hint]
    • A. 

      Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.

    • B. 

      Tides are caused by the 23.5-degree tilt of the Earth's rotational axis to the ecliptic plane.

    • C. 

      Tides are caused on the side of the Earth nearest the Moon because the Moon's gravity attracts the water.

    • D. 

      The Moon's gravity pulls harder on water than on land, because water is less dense than rock.

  • 132. 
    At which lunar phase(s) are tides most pronounced (for example, the highest high tides)? [Hint]
    • A. 

      Both new and full moons

    • B. 

      Full moon only

    • C. 

      Both first and third quarters

    • D. 

      New moon only

    • E. 

      Third quarter moon only

  • 133. 
    • A. 

      Infrared, visible light, ultraviolet, X rays, gamma rays, radio

    • B. 

      Gamma rays, X rays, visible light, ultraviolet, infrared, radio

    • C. 

      Radio, infrared, visible light, ultraviolet, X rays, gamma rays

    • D. 

      Gamma rays, X rays, ultraviolet, visible light, infrared, radio

  • 134. 
    Which forms of light are lower in energy and frequency than the light that our eyes can see? [Hint]
    • A. 

      Infrared and ultraviolet

    • B. 

      Infrared and radio

    • C. 

      Visible light

    • D. 

      Ultraviolet and X rays

  • 135. 
    • A. 

      Frequencies

    • B. 

      Gamma rays

    • C. 

      Photons

    • D. 

      Wavicles

  • 136. 
    Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)? [Hint]
    • A. 

      They have different atomic mass numbers.

    • B. 

      They have different numbers of protons in their nucleus.

    • C. 

      They have different numbers of electrons.

    • D. 

      They have different names.

  • 137. 
    • A. 

      Atomic number = 7; atomic mass number = 13.

    • B. 

      Atomic number = 6; atomic mass number = 7.

    • C. 

      Atomic number = 13; atomic mass number = 6.

    • D. 

      Atomic number = 6; atomic mass number = 13.

  • 138. 
    If we say that a material is opaque to ultraviolet light, we mean that it _________. [Hint]
    • A. 

      Emits ultraviolet light

    • B. 

      Absorbs ultraviolet light

    • C. 

      Reflects ultraviolet light

    • D. 

      Transmits ultraviolet light

  • 139. 
    Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum? [Hint]
    • A. 

      The only way to decide is to make a graph of the intensity of the light at every wavelength, and then analyze the graph carefully.

    • B. 

      The emission line spectrum is produced by electrons jumping up in energy level, while the absorption line spectrum is produced by electrons jumping down in energy level.

    • C. 

      An emission line spectrum consists of a long bright line, while an absorption line spectrum consists of a long dark line.

    • D. 

      An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.

  • 140. 
    An atom that has fewer electrons than protons is called a/an _________. [Hint]
    • A. 

      Ion

    • B. 

      Plasma

    • C. 

      Solid

    • D. 

      Molecule

  • 141. 
    Thermal radiation is defined as _________. [Hint]
    • A. 

      Radiation in the form of emission lines from an object

    • B. 

      Radiation that is felt as heat

    • C. 

      Radiation produced by an extremely hot object

    • D. 

      Radiation with a spectrum whose shape depends only on the temperature of the emitting object

  • 142. 
    According to the laws of thermal radiation, hotter objects emit photons with _________. [Hint]
    • A. 

      A lower average frequency

    • B. 

      A shorter average wavelength

    • C. 

      A higher average speed

    • D. 

      A lower average energy

  • 143. 
    Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you? [Hint]
    • A. 

      The Doppler shift of the star's spectrum

    • B. 

      The peak energy of the star's thermal radiation

    • C. 

      The wavelengths of spectral lines in the star's spectrum

    • D. 

      Whether the star's spectrum has more emission lines or more absorption lines

  • 144. 
    The spectra of most galaxies show redshifts. This means that their spectral lines _________. [Hint]
    • A. 

      Have wavelengths that are longer than normal

    • B. 

      Have wavelengths that are shorter than normal

    • C. 

      Have a higher intensity in the red part of the spectrum

    • D. 

      Always are in the red part of the visible spectrum

  • 145. 
    • A. 

      About 1 milliarcsecond

    • B. 

      About 1 arcsecond (1/3600 of a degree)

    • C. 

      About 1 degree

    • D. 

      About 1 arcminute, or 1/60 of a degree

  • 146. 
    Which of the following statements best describes the two principle advantages of telescopes over eyes? [Hint]
    • A. 

      Telescopes can collect far more light with far better angular resolution.

    • B. 

      Telescopes can collect far more light with far greater magnification.

    • C. 

      Telescopes collect more light and are unaffected by twinkling.

    • D. 

      Telescopes have much more magnification and better angular resolution.

  • 147. 
    • A. 

      Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.

    • B. 

      Light pollution means contamination of light caused by chemicals in the Earth's atmosphere.

    • C. 

      Light pollution refers to lights from human sources that make it difficult to see the stars at night.

    • D. 

      Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium.

  • 148. 
    The stars in our sky twinkle in brightness and color because of _________. [Hint]
    • A. 

      The bubbling and boiling of gases on the surfaces of stars

    • B. 

      Rapid changes in the brightnesses and colors of stars caused by changes in their spectra

    • C. 

      Light pollution

    • D. 

      Turbulence in the Earth's atmosphere

  • 149. 
    • A. 

      It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere.

    • B. 

      It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects.

    • C. 

      It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

    • D. 

      It allows several small telescopes to work together like a single larger telescope.

  • 150. 
    • A. 

      It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.

    • B. 

      It allows two or more small telescopes to achieve a larger light-collecting area than they would have independently.

    • C. 

      It reduces the twinkling of stars caused by atmospheric turbulence.

    • D. 

      It is designed to prevent light pollution from interfering with astronomical observations.

  • 151. 
    Which of the following best describes why we say that light is an electromagnetic wave? [Hint]
    • A. 

      Light is produced only when massive fields of electric and magnetic energy collide with one another.

    • B. 

      The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

    • C. 

      Light can be produced only by electric or magnetic appliances.

    • D. 

      The passage of a light wave can cause electrically charged particles to move up and down.

  • 152. 
    Which of the following statements about X rays and radio waves is NOT true? [Hint]
    • A. 

      X rays travel through space faster than radio waves.

    • B. 

      X rays and radio waves are both forms of light, or electromagnetic radiation.

    • C. 

      X rays have higher frequency than radio waves.

    • D. 

      X rays have shorter wavelengths than radio waves.

  • 153. 
    Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend? [Hint]
    • A. 

      To the Sun

    • B. 

      Several kilometers

    • C. 

      Several centimeters

    • D. 

      A few meters

  • 154. 
    Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element? [Hint]
    • A. 

      Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electronsAtom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons

    • B. 

      Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electronsAtom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons

    • C. 

      Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electronsAtom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons

    • D. 

      Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electronsAtom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons

  • 155. 
    Which of the following statements is true of green grass? [Hint]
    • A. 

      It transmits all colors of light except green.

    • B. 

      It absorbs red light and emits green light.

    • C. 

      It absorbs red light and reflects green light.

    • D. 

      It means the lawn is healthy.

  • 156. 
    Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? [Hint]
    • A. 

      The cloud is cool and very dense, so that you cannot see any objects that lie behind it.

    • B. 

      The cloud is extremely hot.

    • C. 

      The cloud is cool and lies between you and a hot star.

    • D. 

      The cloud is visible primarily because it reflects light from nearby stars.

  • 157. 
    The following diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. Which labeled transition represents an electron that absorbs a photon with 10.2 eV of energy? [Hint]
    • A. 

      D

    • B. 

      E

    • C. 

      A

    • D. 

      B

    • E. 

      C

  • 158. 
    If an electron at level 1 in a hydrogen atom absorbs 10.2 eV of energy, it moves to level 2. What typically happens next? [Hint]
    • A. 

      The electron remains in level 2 until it absorbs an additional 10.2 eV of energy.

    • B. 

      A different electron drops into level 1, since it is now unoccupied.

    • C. 

      The electron returns to level 1 by emitting an ultraviolet photon with 10.2 eV of energy.

    • D. 

      The electron jumps to level 3 as soon as it absorbs any additional energy.

  • 159. 
    Which of the following statements about thermal radiation is always true? [Hint]
    • A. 

      A cold object produces more total infrared and radio emission per unit surface area than a hot object.

    • B. 

      A hot object produces more total infrared emission than a cooler object.

    • C. 

      A hot object emits more radiation per unit surface area than a cool object.

    • D. 

      All the light emitted by hot object has higher energy than the light emitted by a cooler object.

  • 160. 
    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? [Hint]
    • A. 

      It is much more massive than the Sun.

    • B. 

      Its surface is cooler than the surface of the Sun.

    • C. 

      It is moving away from us.

    • D. 

      It is much brighter than the Sun.

  • 161. 
    From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 486.0 nm. What can we conclude? [Hint]
    • A. 

      The star is getting hotter.

    • B. 

      The star is moving toward us.

    • C. 

      The star is getting colder.

    • D. 

      The star is moving away from us.

  • 162. 
    Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude? [Hint]
    • A. 

      Star X is moving away from us faster than Star Y.

    • B. 

      Star X is hotter than Star Y.

    • C. 

      Star X is moving away from us and Star Y is moving toward us.

    • D. 

      Star X is coming toward us faster than Star Y.

    • E. 

      Star Y is moving away from us faster than Star X.

  • 163. 
    Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which one? [Hint]
    • A. 

      Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us.

    • B. 

      The peak of the star's thermal emission tells us its temperature: hotter stars peak at shorter (bluer) wavelengths.

    • C. 

      We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.

    • D. 

      The total amount of light in the spectrum tells us the star's radius.

  • 164. 
    Suppose that the angular separation of two stars is 0.1 arcseconds, and you photograph them with a telescope that has an angular resolution of 1 arcsecond. How will the stars appear in the photograph? [Hint]
    • A. 

      The two stars will appear to be touching, looking rather like a small dumbbell.

    • B. 

      Since their angular separation is smaller than the telescope's angular resolution, you will not be able to see these stars at all in your photograph.

    • C. 

      You will see two distinct stars in your photograph, separated from one another by a distance of 1 arcsecond.

    • D. 

      Since their angular separation is smaller than the telescope's angular resolution, your photograph will seem to show only one star rather than two.

  • 165. 
    • A. 

      The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope.

    • B. 

      The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

    • C. 

      The answer cannot be determined from the information given in the question.

    • D. 

      The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope.

  • 166. 
    Which of the following is NOT an advantage of the Hubble Space Telescope over ground-based telescopes? [Hint]
    • A. 

      It can observe infrared and ultraviolet light, as well as visible light.

    • B. 

      It never has to close because of cloudy skies.

    • C. 

      Stars do not twinkle when observed from space.

    • D. 

      It is closer to the stars.

  • 167. 
    The Chandra X-ray Observatory must operate in space because: [Hint]
    • A. 

      It was built by NASA.

    • B. 

      X-ray telescopes require the use of grazing incidence mirrors.

    • C. 

      X rays do not penetrate Earth's atmosphere.

    • D. 

      X rays are too dangerous to be allowed on the ground.

  • 168. 
    Which of the following is always true about images captured with X-ray telescopes? [Hint]
    • A. 

      They show us light with extremely long wavelengths compared to the wavelengths of visible light.

    • B. 

      They are always very pretty.

    • C. 

      They are always shown with colors that are not the true colors of the objects that were photographed.

    • D. 

      They always have very high angular resolution.

    • E. 

      They always are made with adaptive optics.

  • 169. 
    Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun? [Hint]
    • A. 

      Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto

    • B. 

      Earth, Mars, Mercury, Venus, Jupiter, Saturn, Uranus, Neptune, Pluto

    • C. 

      Mercury, Venus, Mars, Earth, Saturn, Jupiter, Neptune, Uranus, Pluto

    • D. 

      Mercury, Earth, Venus, Mars, Jupiter, Saturn, Neptune, Uranus, Pluto

  • 170. 
    Suppose you view the solar system from high above Earth's north pole. Which of the following statements about planetary orbits will be true? [Hint]
    • A. 

      All the planets except Uranus orbit the Sun counterclockwise; Uranus orbits in the opposite direction.

    • B. 

      All the planets orbit counterclockwise around the Sun.

    • C. 

      The inner planets orbit the Sun counterclockwise while the outer planets orbit the Sun clockwise.

    • D. 

      The inner planets orbit the Sun clockwise while the outer planets orbit the Sun counterclockwise.

  • 171. 
    Which of the following statements about our Sun is NOT true? [Hint]
    • A. 

      Its diameter is about 5 times that of Earth.

    • B. 

      It is a star.

    • C. 

      It is made mostly of hydrogen and helium.

    • D. 

      It contains more than 99% of all the mass in our solar system.

  • 172. 
    Which of the following statements about Mars is NOT true? [Hint]
    • A. 

      It is frozen today, but once had flowing water.

    • B. 

      It is considered part of our inner solar system.

    • C. 

      We have landed spacecraft on its surface.

    • D. 

      We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks.

  • 173. 
    The planet in our solar system with the highest average surface temperature is _________. [Hint]
    • A. 

      Neptune

    • B. 

      Mercury

    • C. 

      Venus

    • D. 

      Earth

  • 174. 
    The terrestrial planets in our solar system are _________. [Hint]
    • A. 

      Mercury, Venus, Earth, and Mars

    • B. 

      Mercury, Venus, Earth, Mars, and Pluto

    • C. 

      Jupiter, Saturn, Uranus, Neptune, and Pluto

    • D. 

      Jupiter, Saturn, Uranus, and Neptune

  • 175. 
    The jovian planets in our solar system are _________. [Hint]
    • A. 

      Jupiter, Saturn, Uranus, and Neptune

    • B. 

      Jupiter, Saturn, Uranus, Neptune, and Pluto

    • C. 

      Io, Europa, Ganymede, and Callisto

    • D. 

      Mercury, Venus, Earth, and Mars

  • 176. 
    • A. 

      Water

    • B. 

      Carbon dioxide

    • C. 

      Ammonia

    • D. 

      Methane

  • 177. 
    In essence, the nebular theory holds that _________. [Hint]
    • A. 

      Our solar system formed from the collapse of an interstellar cloud of gas and dust

    • B. 

      The planets each formed from the collapse of its own separate nebula

    • C. 

      The nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our Sun and another star.

    • D. 

      Nebulae are clouds of gas and dust in space

  • 178. 
    According to modern science, what was the approximate chemical composition of the solar nebula? [Hint]
    • A. 

      50% hydrogen and helium, 50% everything else

    • B. 

      98% hydrogen and helium, 2% everything else

    • C. 

      98% hydrogen, 2% helium

    • D. 

      Roughly equal proportions of hydrogen, helium, water, and methane

  • 179. 
    According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? [Hint]
    • A. 

      It got hotter, its rate of rotation increased, and it flattened into a disk.

    • B. 

      It gained energy, it gained angular momentum, and it flattened into a disk.

    • C. 

      Its mass, temperature, and density all increased.

    • D. 

      Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the jovian planets, and central temperatures rose to more than a trillion Kelvin.

  • 180. 
    Which of the following types of material can condense into what we call ice at low temperatures? [Hint]
    • A. 

      Hydrogen and helium

    • B. 

      Rock

    • C. 

      Metal

    • D. 

      Hydrogen compounds

  • 181. 
    • A. 

      It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

    • B. 

      It is another way of stating the temperature at which water freezes into ice.

    • C. 

      It is the altitude in a planet's atmosphere at which snow can form.

    • D. 

      It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds.

  • 182. 
    • A. 

      The solidification of ices, rocks, and metal from the gas of the solar nebular

    • B. 

      The growth of the Sun as the density of gas increased in the center of the solar nebula

    • C. 

      The formation of moons around planets

    • D. 

      The growth of planetesimals from smaller solid particles that collided and stuck together

  • 183. 
    According to our theory of solar system formation, what are asteroids and comets? [Hint]
    • A. 

      Chunks of rock or ice that were expelled from planets by volcanoes

    • B. 

      Leftover planetesimals that never accreted into planets

    • C. 

      The shattered remains of collisions between planets

    • D. 

      Chunks of rock or ice that condensed after the planets and moons finished forming

  • 184. 
    • A. 

      The time during which heavy elements condensed into rock and metal in the solar nebula

    • B. 

      The first few hundred million years after the planets formed, which is when most impact craters were formed

    • C. 

      The time before planetesimals finished accreting into planets, during which many growing planetesimals must have shattered in collisions

    • D. 

      The period about 65 million years ago when an impact is thought to have led to the extinction of the dinosaurs

  • 185. 
    • A. 

      The Moon formed when two gigantic asteroids collided with one another.

    • B. 

      The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object.

    • C. 

      The Moon formed just like the Earth, from accretion in the solar nebula.

    • D. 

      The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth.

  • 186. 
    According to modern scientific dating techniques, approximately how old is the solar system? [Hint]
    • A. 

      10,000 years

    • B. 

      4.6 billion years

    • C. 

      4.6 million years

    • D. 

      14 billion years

  • 187. 
    • A. 

      A planet that orbits a star that is not our own Sun

    • B. 

      A planet that is considered an "extra," in that it was not needed for the formation of its solar system

    • C. 

      A planet that is larger than the Sun

    • D. 

      A planet that is extra large compared to what we'd expect

  • 188. 
    Which of the following best describes how we have discovered nearly all of the more than 100 extrasolar planets known to date? [Hint]
    • A. 

      New, powerful telescopes have allowed us to find these planets by taking photographs of them.

    • B. 

      The planets have been observed with infrared and X-ray telescopes.

    • C. 

      They have all been discovered with the Hubble Space Telescope.

    • D. 

      We have not seen the planets directly, but rather have seen slight motions of stars that we attribute to the gravitational influence of orbiting planets.

  • 189. 
    Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is _________. [Hint]
    • A. 

      Just slightly less

    • B. 

      Much smaller

    • C. 

      About the same

    • D. 

      Much larger

  • 190. 
    • A. 

      It explains why the Sun is so massive.

    • B. 

      It explains the fact that the Sun generates thermal energy by losing some 4 million tons of mass each day.

    • C. 

      It explains why the Sun has a magnetic field strong enough influence the atmospheres of the planets.

    • D. 

      It explains why the Sun's surface temperature is about 6,000 °C.

  • 191. 
    In what way is Venus most similar to Earth? [Hint]
    • A. 

      Both planets have warm days and cool nights.

    • B. 

      Both planets are nearly the same size.

    • C. 

      Both planets have very similar atmospheres.

    • D. 

      Both planets have similar surface geology.

  • 192. 
    Imagine that an alien spaceship crashed onto Earth. Which statement would most likely to be true? [Hint]
    • A. 

      It would crash in the ocean.

    • B. 

      The crash would create a noticeable crater.

    • C. 

      The aliens' home world is another planet in our own solar system.

    • D. 

      All the evidence of the crash would be quickly whisked off by the U.S. military to Area 51 in Nevada.

  • 193. 
    Which of the following is NOT a major pattern of motion in the solar system? [Hint]
    • A. 

      The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun.

    • B. 

      Most of the solar system's large moons orbit in their planet's equatorial plane.

    • C. 

      All of the planets orbit the Sun in the same direction --- counterclockwise as viewed from above Earth's north pole.

    • D. 

      Nearly all comets orbit the Sun in same direction and roughly the same plane.

  • 194. 
    Which of the following is NOT a major difference between the terrestrial and jovian planets in our solar system? [Hint]
    • A. 

      Terrestrial planets orbit much closer to the Sun than jovian planets.

    • B. 

      Terrestrial planets contain large quantities of ice and jovian planets do not.

    • C. 

      Jovian planets have rings and many moons, while terrestrial planets have few moons (if any) and no rings.

    • D. 

      Jovian planets contain huge amounts of hydrogen and helium gas, while these gases are quite rare on terrestrial planets.

  • 195. 
    The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
    • A. 

      The diameter of Earth's Moon is about 1/4 that of Earth.

    • B. 

      Jupiter has a very small axis tilt.

    • C. 

      Saturn has no solid surface.

    • D. 

      Venus does not have a moon.

  • 196. 
    • A. 

      These first-generation star systems typically had several terrestrial planets in addition to jovian planets.

    • B. 

      There were no comets or asteroids in these first-generation star systems.

    • C. 

      Jovian planets in these first-generation star systems had clouds made of water and other hydrogen compounds.

    • D. 

      Like the jovian planets in our solar system, the jovian planets in these first-generation systems were orbited by rings.

  • 197. 
    According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size? [Hint]
    • A. 

      Einstein's law that E = mc2.

    • B. 

      The law of conservation of angular momentum

    • C. 

      The law of universal gravitation

    • D. 

      The law of conservation of energy

  • 198. 
    According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system? [Hint]
    • A. 

      Because gravity was stronger in the outer solar system, allowing more solid material to collect.

    • B. 

      Because only the outer planets captured hydrogen and helium gas from the solar nebula.

    • C. 

      Because gas in the outer solar system contained a larger proportion of rock, metal, and hydrogen compound than the gas in the inner solar system.

    • D. 

      Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system.

  • 199. 
    According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons? [Hint]
    • A. 

      As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.

    • B. 

      Because of their strong gravity, the jovian planets were able to capture numerous asteroids that happened to be passing nearby, and these became the major moons of the jovian planets.

    • C. 

      The many moons of the jovian planets remains one of the unexplained mysteries of the formation of our solar system.

    • D. 

      The large moons of the jovian planets were originally formed in the inner solar system, and these moons migrated out to join up with the jovian planets.

  • 200. 
    Which of the following is NOT evidence supporting the idea that our Moon formed as a result of a giant impact? [Hint]
    • A. 

      Computer simulations show that the Moon could really have formed in this way.

    • B. 

      The Pacific Ocean appears to be a large crater --- probably the one made by the giant impact.

    • C. 

      The Moon's average density suggests it is made of rock much more like that of the Earth's outer layers than that of the Earth as a whole.

    • D. 

      The Moon has a much smaller proportion of easily vaporized materials than Earth.

  • 201. 
    We know that the Earth has water. However, according to our theory of solar system formation, the inner solar system was too hot for hydrogen compounds like water to condense. What do we conclude? [Hint]
    • A. 

      We conclude that Earth's water likely was brought here by asteroids or comets that formed beyond the frost line.

    • B. 

      We conclude that our theory of solar system formation will need modification, because it is unable to account for the existence of water on Earth.

    • C. 

      We conclude that the water arrived at a time when it rained throughout the inner solar system.

    • D. 

      We conclude that Earth's water probably originated through chemical reactions among the rock and metal of Earth's interior.

  • 202. 
    • A. 

      You'll have 0.75 kilogram of the radioactive substance remaining.

    • B. 

      You'll have 0.25 kilogram of the radioactive substance remaining.

    • C. 

      All the material will have completely decayed.

    • D. 

      You'll have 0.5 kilogram of the radioactive substance remaining.

  • 203. 
    • A. 

      Radiometric dating of meteorites.

    • B. 

      Radiometric dating of Moon rocks.

    • C. 

      Radiometric dating of the oldest Earth rocks.

    • D. 

      From theoretical calculations based on how long it must have taken the planets to evolve to their present forms.

  • 204. 
    Which of the following statements is NOT true about the planets so far discovered around other stars? [Hint]
    • A. 

      Most of them have been discovered by observing Doppler shifts in the spectra of the stars they orbit.

    • B. 

      Photographs reveal that most of them have atmospheres much like that of Jupiter.

    • C. 

      Most (or possibly all) of them are much more massive than Earth.

    • D. 

      Many of them orbit closer to their star than Jupiter orbits the Sun.

  • 205. 
    Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets? [Hint]
    • A. 

      Jovian planets can migrate from the orbits in which they are born.

    • B. 

      Some of the "exceptions to the rules" in our own solar system are likely to have been the result of giant impacts.

    • C. 

      In addition to the categories of terrestrial and jovian, there must be an "in-between" category of planet that has the mass of a jovian planet but the composition of a terrestrial planet.

    • D. 

      In some star systems, it is possible for jovian planets to form in the inner solar system and terrestrial planets to form in the outer solar system.

  • 206. 
    You observe a star, a star very similar to our own Sun in size and mass. You find that this star wobbles very slightly back and forth once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet? [Hint]
    • A. 

      The planet must have a mass about the same as the mass of Jupiter.

    • B. 

      You do not have enough information to say anything at all about the planet.

    • C. 

      The planet must be closer to the star than Earth is to the Sun.

    • D. 

      The planet must be farther from the star than Pluto is from the Sun.

  • 207. 
    The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned in this chapter, what is the most likely explanation for the lack of asteroids between Mercury and Mars? [Hint]
    • A. 

      Gravity was too weak to allow asteroids to form in this part of the solar system.

    • B. 

      There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.

    • C. 

      It was too hot for asteroids to form in this part of the solar system.

    • D. 

      All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter.

  • 208. 
    Based on everything you have learned in this chapter, which of the following statements seems unlikely to be true?
    • A. 

      Just as is the case in our solar system, other planetary systems will have far more numerous asteroids and comets than actual planets.

    • B. 

      Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

    • C. 

      Like the planets in our solar system, planets in other star systems will all orbit their star in the same direction and approximately the same plane.

    • D. 

      Other solar systems will also have planets in the two basic categories of terrestrial and jovian.

  • 209. 
    Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of _________. [Hint]
    • A. 

      A dust speck to a basketball

    • B. 

      A dust speck to a golf ball

    • C. 

      A golf ball to a baseball

    • D. 

      A golf ball to a beach ball

  • 210. 
    From center to surface, which of the following correctly lists the interior layers of a terrestrial world? [Hint]
    • A. 

      Core, crust, lithosphere

    • B. 

      Mantle, core, crust

    • C. 

      Mantle, crust, core

    • D. 

      Core, mantle, crust

  • 211. 
    • A. 

      The five terrestrial worlds all started similarly but ended up looking quite different.

    • B. 

      They lost interior heat to outer space.

    • C. 

      At a time when their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.

    • D. 

      Their surfaces show a variety of different geological features resulting from different geological processes.

  • 212. 
    • A. 

      It is a layer of hot, molten rock encompassing the core and part of the mantle.

    • B. 

      It is the outer layer of relatively strong, rigid rock, encompassing the crust and part of the mantle.

    • C. 

      It is a thin layer of rock that lies between the mantle and crust.

    • D. 

      It is the interior region of a planet in which a magnetic field is generated.

  • 213. 
    • A. 

      The region in a planet's atmosphere where aurorae occur

    • B. 

      The uppermost layer of any planetary atmosphere

    • C. 

      A region of space around a planet in which the planet's magnetic field can trap charged particles

    • D. 

      The layer of a planet in which its magnetic field is generated

  • 214. 
    The processes responsible for virtually all surface geology are _________. [Hint]
    • A. 

      Eruptions, lava flows, and outgassing

    • B. 

      Accretion, differentiation, and radioactive decay

    • C. 

      Impact cratering, volcanisms, tectonics, and erosion

    • D. 

      Convection, conduction, and radiation

  • 215. 
    In the context of planetary geology, what do we mean by outgassing? [Hint]
    • A. 

      The loss of atmospheric gas to outer space

    • B. 

      The evaporation of water that adds water vapor (a gas) to an atmosphere

    • C. 

      The release by volcanism of gases that had been trapped in a planetary interior

    • D. 

      Outgassing is simply another name for a volcanic eruption.

  • 216. 
    Which of the following is the most basic definition of a greenhouse gas? [Hint]
    • A. 

      A gas that reflects a lot of sunlight

    • B. 

      A gas that absorbs infrared light

    • C. 

      A gas that makes a planet much hotter than it would be otherwise, even in small amounts

    • D. 

      A gas that keeps warms air from rising, and therefore warms the surface

  • 217. 
    Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is _________. [Hint]
    • A. 

      About the thickness of a sheet of paper

    • B. 

      About an inch thick

    • C. 

      About a half-inch thick

    • D. 

      About 6 inches thick

  • 218. 
    Which of the following best describes the lunar maria? [Hint]
    • A. 

      Densely cratered regions on the Moon

    • B. 

      Frozen oceans of liquid water on the Moon

    • C. 

      Mountainous regions on the Moon

    • D. 

      Relatively smooth, flat plains on the Moon

  • 219. 
    • A. 

      It is made by the same processes that make powdery sand on Earth.

    • B. 

      It is the result of countless tiny impacts by small particles striking the Moon.

    • C. 

      Recent, large impacts shattered lunar rock to make this soil.

    • D. 

      It exists because the Moon accreted from powdery material after a giant impact blasted the Earth.

  • 220. 
    • A. 

      The presence of many impact craters

    • B. 

      The presence of many long, tall cliffs

    • C. 

      Mercury's unusually high density

    • D. 

      The characteristics of the Caloris Basin

  • 221. 
    Olympus Mons is ______. [Hint]
    • A. 

      A huge volcano on Mars

    • B. 

      A large lava plain on the Moon

    • C. 

      A huge volcano on Venus

    • D. 

      A great canyon on Mars

  • 222. 
    Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface? [Hint]
    • A. 

      The presence of features that look like dried up river beds

    • B. 

      The presence of small, residual pools of water on volcanic plains, recently visited by Mars rovers

    • C. 

      The presence of very old craters that appear to have been eroded by rain

    • D. 

      The presence of what looks like sedimentary layers in some crater bottoms

  • 223. 
    Based on its surface features, the most important event on Venus in the past billion years or so was _________. [Hint]
    • A. 

      The impact of an unusually large asteroid that left a deep scar on one side of the planet

    • B. 

      A global "repaving" that erased essentially all the surface features that had existed earlier

    • C. 

      The onset of mantle convection, which caused Venus's lithosphere to split into plates like those on Earth

    • D. 

      The eruption of a giant volcano that formed one of Venus's "continents"

  • 224. 
    • A. 

      It gets its name because it heats a planet like a greenhouse effect, but it involves a completely different mechanism of heating that doesn't actually involve greenhouse gases.

    • B. 

      A greenhouse effect that heats a planet so much that its surface rock melts

    • C. 

      A greenhouse effect that starts on a planet but later disappears as gases are lost to space

    • D. 

      A greenhouse effect that keeps getting stronger until all a planet's greenhouse gases are in its atmosphere

  • 225. 
    • A. 

      Seafloor crust is thicker, older, and higher in density.

    • B. 

      Seafloor crust is thicker, younger, and lower in density.

    • C. 

      Seafloor crust is thinner, older, and lower in density.

    • D. 

      Seafloor crust is thinner, younger, and higher in density.

  • 226. 
    • A. 

      It makes the growth of continents possible.

    • B. 

      It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.

    • C. 

      It will prevent us from suffering any consequences from global warming.

    • D. 

      It allows for an ultraviolet-absorbing stratosphere.

  • 227. 
    • A. 

      Because we are responsible for many forest fires

    • B. 

      Because we have released large quantities of CFCs into the atmosphere

    • C. 

      Because we are increasing the concentration of greenhouse gases in Earth's atmosphere.

    • D. 

      Because our politicians spout a lot of hot air.

  • 228. 
    Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny? [Hint]
    • A. 

      Whether or not it has liquid water

    • B. 

      Its distance from the Sun

    • C. 

      Its composition

    • D. 

      Its size

  • 229. 
    The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that _________. [Hint]
    • A. 

      Earth contains more metal than the Moon

    • B. 

      A large baked potato takes longer to cool than a small baked potato

    • C. 

      Gas bubbles form and rise upward in boiling water

    • D. 

      Thunderstorms tend to form on hot summer days

  • 230. 
    Suppose we had some kind of device that allowed us to see Earth's interior. If we focused on the mantle to observe mantle convection, what would we see happening? [Hint]
    • A. 

      Hot molten rock rapidly rising upward throughout the mantle, as cool solid rock falls downward

    • B. 

      Dense metals falling downward while low-density rock rises upward

    • C. 

      Not much --- on human time scales, mantle convection is barely noticeable.

    • D. 

      A rapid, up and down churning of the material in the mantle

  • 231. 
    Which of the following most likely explains why Venus does NOT have a global magnetic field like Earth? [Hint]
    • A. 

      It does not have a metallic core.

    • B. 

      Its rotation is too slow.

    • C. 

      It has too thick of an atmosphere.

    • D. 

      Unlike Earth, Venus does not have a liquid outer core.

  • 232. 
    • A. 

      A dense core and plate tectonics

    • B. 

      Mantle convection and a thick atmosphere.

    • C. 

      Plate tectonics and widespread erosion

    • D. 

      Significant volcanism and tectonics

  • 233. 
    Which of the following general statements about Earth's atmosphere is NOT true? [Hint]
    • A. 

      Without the relatively rare gas called ozone, Earth's surface would be bathed in dangerous ultraviolet light from the Sun.

    • B. 

      The oxygen in our atmosphere was released by living organisms.

    • C. 

      The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.

    • D. 

      Gas high in the atmosphere absorbs dangerous X rays from the Sun.

  • 234. 
    • A. 

      Because molecules scatter red light more effectively than blue light

    • B. 

      Because deep space is blue in color.

    • C. 

      Because the Sun emits mostly blue light

    • D. 

      No one knows --- this is one of the great mysteries of science.

    • E. 

      Because gas molecules in the atmosphere scatter blue light more effectively than red light

  • 235. 
    Which of the following best describes how the greenhouse effect works? [Hint]
    • A. 

      The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light and thereby makes the atmosphere much hotter than it would be otherwise.

    • B. 

      Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight heats the lower atmosphere and the surface.

    • C. 

      Greenhouse gases absorb X rays and ultraviolet light from the Sun, and this absorbed radiation then heats the atmosphere and the surface.

    • D. 

      A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.

  • 236. 
    Suppose that Earth's atmosphere had no greenhouse gases. Then the Earth's average surface temperature would be _________. [Hint]
    • A. 

      Slightly cooler, but still above freezing

    • B. 

      Some 30°C cooler, which means well below the freezing point of water

    • C. 

      Slightly warmer, but still below the boiling point of water

    • D. 

      About the same as it is now

  • 237. 
    Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude? [Hint]
    • A. 

      Erosion affects the maria more than it affects other regions of the Moon.

    • B. 

      The maria formed after the heavy bombardment ended.

    • C. 

      The maria formed within the past 1 billion years.

    • D. 

      The regions of the maria were hit by fewer impacts than the densely cratered regions.

  • 238. 
    Which of the following best describes the geological histories of the Moon and Mercury? [Hint]
    • A. 

      Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

    • B. 

      Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics.

    • C. 

      All four geological processes were important in their early histories, but only impact cratering still reshapes their surfaces today.

    • D. 

      Impact cratering is the only major geological process that has affected their surfaces.

  • 239. 
    • A. 

      The fact that parts of Mars have a lot of craters tell us that Mars must once have been much warmer.

    • B. 

      The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.

    • C. 

      We think it for purely theoretical reasons, based on calculations showing that the Sun has brightened with time.

    • D. 

      The presence of inactive volcanoes on Mars tells us that there must once have been a lot of outgassing, and hence a thicker atmosphere.

  • 240. 
    All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space? [Hint]
    • A. 

      Mars probably once had a much higher density of greenhouse gases in its atmosphere than it does today.

    • B. 

      The rock on Mars is probably red because of chemical reactions with oxygen that had been released into the atmosphere through the outgassing of water molecules.

    • C. 

      Mars lost any global magnetic field that it may once have had.

    • D. 

      The axis tilt of Mars is thought to change significantly with time.

  • 241. 
    According to current science, why is Mars red? [Hint]
    • A. 

      The red color of Mars is a result of the scattering of light in the Martian sky.

    • B. 

      The red color is caused by water ice chemically bound in surface rock.

    • C. 

      Martian volcanoes released a much redder lava than volcanoes on Earth.

    • D. 

      Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface.

  • 242. 
    All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450°C hotter than the surface of Earth? [Hint]
    • A. 

      Venus has a much stronger greenhouse effect than Earth.

    • B. 

      Venus is only about 73% as far from the Sun as Earth.

    • C. 

      Venus has a higher atmospheric pressure than Earth.

    • D. 

      Venus has a much higher reflectivity than Earth.

  • 243. 
    Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it? [Hint]
    • A. 

      The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle

    • B. 

      The smaller size of Venus, which has allowed it to lose much more internal heat than Earth

    • C. 

      The slow rotation of Venus

    • D. 

      The apparent lack of plate tectonics on Venus

  • 244. 
    Which of the following best explain what we think happened to outgassed water on Venus? [Hint]
    • A. 

      It is frozen in craters near the poles.

    • B. 

      It turned into carbon dioxide by reacting with nitrogen in Venus's atmosphere.

    • C. 

      Ultraviolet light split the water molecules, and the hydrogen then escaped to space.

    • D. 

      Water was removed from the atmosphere by chemical reactions with surface rock.

  • 245. 
    • A. 

      Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.

    • B. 

      Chemical reactions turned Earth's carbon dioxide into nitrogen.

    • C. 

      Earth once had a lot of carbon dioxide, but it was lost to space during the heavy bombardment early in our solar system's history.

    • D. 

      Earth's volcanoes outgassed far less carbon dioxide than those on Venus.

  • 246. 
    • A. 

      Active volcanism and active tectonics

    • B. 

      Life and atmospheric oxygen

    • C. 

      Life and active volcanism

    • D. 

      Plate tectonics and liquid water oceans

  • 247. 
    Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal? [Hint]
    • A. 

      Cooler temperatures cause volcanoes to become more active, so they release more carbon dioxide into the atmosphere than they do when temperatures are warmer.

    • B. 

      Cooler temperatures allow carbon dioxide to form rain and rain out of the atmosphere.

    • C. 

      Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.

    • D. 

      Cooler temperatures mean more ice and more erosion, which somehow makes the planet warm up.

  • 248. 
    Which of the following would NOT be an expected consequence of global warming? [Hint]
    • A. 

      Melting of polar ice and glaciers.

    • B. 

      The entire Earth will warm up by the same amount.

    • C. 

      An increase in the severity of winter blizzards.

    • D. 

      An increase in the number and intensity of hurricanes.

  • 249. 
    Which of the following is NOT a general characteristic of the four jovian planets in our solar system? [Hint]
    • A. 

      They are much more massive then any of the terrestrial planets.

    • B. 

      They lack solid surfaces.

    • C. 

      They are composed mainly of hydrogen, helium, and hydrogen compounds.

    • D. 

      They are higher in average density than are the terrestrial planets.

  • 250. 
    • A. 

      Liquid core of hydrogen compounds; liquid hydrogen layer; metallic hydrogen layer; gaseous hydrogen layer; cloud layer

    • B. 

      Core of rock and metal; mantle of lower density rock; upper layer of gaseous hydrogen; cloud layer

    • C. 

      Solid rock core; layer of solid metallic hydrogen; layer of pure liquid hydrogen; cloud layer

    • D. 

      Core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer

  • 251. 
    Which of the following statements comparing the jovian interiors is NOT thought to be true? [Hint]
    • A. 

      They all have cores that contain at least some rock and metal.

    • B. 

      They all have cores of roughly the same mass.

    • C. 

      Deep inside them, they all have pressures far higher than that found on the bottom of the ocean on Earth.

    • D. 

      They all have the same exact set of internal layers, though these layers differ in size.

  • 252. 
    Overall, Jupiter's composition is most like that of _________. [Hint]
    • A. 

      A comet

    • B. 

      The Sun

    • C. 

      Earth

    • D. 

      An asteroid

  • 253. 
    Jupiter's colors come in part from its three layers of clouds. Which of the following is NOT the primary constituent of one of Jupiter's cloud layers? [Hint]
    • A. 

      Clouds of sulfuric acid

    • B. 

      Clouds of ammonia

    • C. 

      Clouds of ammonium hydrosulfide

    • D. 

      Clouds of water

  • 254. 
    • A. 

      They are about the same as average winds on Earth.

    • B. 

      They are slightly slower than average winds on Earth.

    • C. 

      They are much faster than hurricane winds on Earth.

    • D. 

      They are slightly faster than average winds on Earth.

  • 255. 
    • A. 

      The Great Red Spot is a hurricane that comes and goes on Jupiter.

    • B. 

      The Great Red Spot is a place where reddish particles from Io impact Jupiter's surface

    • C. 

      The Great Red Spot is a long-lived, high-pressure storm on Jupiter.

    • D. 

      The Great Red Spot is a region on Jupiter where the temperature is so high that the gas glows with red visible light.

  • 256. 
    • A. 

      Water

    • B. 

      Ammonia

    • C. 

      Methane

    • D. 

      Hydrogen

  • 257. 
    • A. 

      Jupiter's magnetic field is about twice as strong as Earth's.

    • B. 

      Jupiter's magnetic field is about 20,000 times as strong as Earth's.

    • C. 

      Jupiter's magnetic field strength is about the same as Earth's.

    • D. 

      Jupiter's magnetic field is much weaker than Earth's.

  • 258. 
    Which of the following statements about the moons of the jovian planets is NOT true? [Hint]
    • A. 

      Many of the moons are made largely of ices.

    • B. 

      The majority of the moons are large enough to be spherical in shape, while only a few have the more potatolike shapes of asteroids.

    • C. 

      Some moons have an atmosphere.

    • D. 

      Some of the moons are big enough that we'd probably call them planets if they orbited the Sun.

  • 259. 
    The most volcanically active body in our solar system is _________. [Hint]
    • A. 

      Triton

    • B. 

      Earth

    • C. 

      Io

    • D. 

      Europa

  • 260. 
    Which moon has a thick atmosphere? [Hint]
    • A. 

      Europa

    • B. 

      Triton

    • C. 

      Titan

    • D. 

      Ganymede

  • 261. 
    Which moon is considered likely to have a deep, subsurface ocean of liquid water? [Hint]
    • A. 

      Triton

    • B. 

      Miranda

    • C. 

      Io

    • D. 

      Europa

  • 262. 
    • A. 

      Io

    • B. 

      Callisto

    • C. 

      Triton

    • D. 

      Titan

  • 263. 
    Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings? [Hint]
    • A. 

      Nothing --- up close, the rings would be so completely invisible that you'd have no way to know they are there. They can be seen only from a distance.

    • B. 

      Countless icy particles, ranging in size from dust grains to large boulders

    • C. 

      Dozens of large "moonlets" made of metal and rock, each a few kilometers across

    • D. 

      A solid, shiny surface, looking much like a piece of a DVD but a lot bigger

  • 264. 
    Which statement about planetary rings is NOT true? [Hint]
    • A. 

      Individual ring particles orbit their planet in accord with Kepler's laws, so that particles closer in orbit faster than particles farther out.

    • B. 

      Rings are always located closer to a planet's surface than any large moons.

    • C. 

      Saturn's rings formed along with its moons 4.6 billion years ago.

    • D. 

      All four jovian planets have rings.

  • 265. 
    Which of the following gases is NOT a significant ingredient of the jovian planet atmospheres? [Hint]
    • A. 

      Helium

    • B. 

      Carbon dioxide

    • C. 

      Hydrogen

    • D. 

      Water

  • 266. 
    Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading? [Hint]
    • A. 

      The materials they are made of are not the kinds of thing we usually think of as gases.

    • B. 

      They really contain relatively little material in a gaseous state. Much more of their mass is liquid, metallic, or in strange high-pressure states that we don't naturally find on Earth.

    • C. 

      Actually, it's a great description, because these worlds are big and gaseous throughout.

    • D. 

      They are not in any sense "giants."

  • 267. 
    • A. 

      It would become a star, with nuclear fusion in its core.

    • B. 

      Its density would increase but its diameter would barely change.

    • C. 

      Its density would stay about the same and its volume would double.

    • D. 

      Its density would decrease and its diameter would double.

  • 268. 
    According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn? [Hint]
    • A. 

      Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.

    • B. 

      Ices were able to condense at the distance of Jupiter and Saturn, but only rock and metal could condense at the distances of Uranus and Neptune.

    • C. 

      The size differences are thought to be a random coincidence.

    • D. 

      The colder gas in the outer regions of the solar nebula had less gravity and therefore could not gather up into such large balls as it could closer in.

  • 269. 
    • A. 

      Jupiter has three different types of wind, each of which makes a different type of cloud.

    • B. 

      The three layers reflect regions of Jupiter's atmosphere with different overall chemical compositions.

    • C. 

      Clouds form randomly, so on average there are always three layers.

    • D. 

      The three layers represent clouds made of gases that condense at different temperatures and therefore different altitudes.

  • 270. 
    Which of the following best describes what is going on in the alternating dark and light "stripes" that we see in photographs of Jupiter and Saturn. [Hint]
    • A. 

      There are three different color stripes corresponding to the three different types of clouds found on these planets.

    • B. 

      Dark stripes are those in which there is a stratosphere and light stripes are those with no stratosphere.

    • C. 

      The dark and light stripes correspond to alternating bands of different chemical composition.

    • D. 

      The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.

  • 271. 
    Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why? [Hint]
    • A. 

      Temperatures on Jupiter and Saturn are too high for methane to condense.

    • B. 

      The rapid rotation of Jupiter and Saturn prevents methane clouds from forming.

    • C. 

      Jupiter and Saturn do not contain any methane gas.

    • D. 

      The stronger gravity on Jupiter and Saturn pulls methane downward so that it can't form clouds.

  • 272. 
    Which jovian planet should have the most extreme seasonal changes? [Hint]
    • A. 

      Saturn

    • B. 

      Uranus

    • C. 

      Jupiter

    • D. 

      Neptune

  • 273. 
    • A. 

      Io's gravity allows this region to capture huge numbers of charged particles from the solar wind.

    • B. 

      The region is full of gases ionized after being expelled from volcanoes on Io.

    • C. 

      An orbital resonance between Io, Europa, and Ganymede makes the radiation intense.

    • D. 

      Jupiter's strong magnetic field makes the radiation intense everywhere, and the region around Io is no different than any other region.

  • 274. 
    Which of the following best explains why so many of the jovian moons have been more geologically active in the past than have the Moon or Mercury? [Hint]
    • A. 

      Jovian moons are made mostly of ice that can melt or deform at much lower temperatures than can the rock and metal that make up the Moon and Mercury.

    • B. 

      The jovian moons are considerably larger than the Moon and Mercury and therefore have retained much more internal heat.

    • C. 

      The jovian moons probably have far more internal heat generated by radioactive decay than do the Moon or Mercury.

    • D. 

      Because of their greater distances from the Sun, the jovian moons receive much less heat from the Sun.

  • 275. 
    All the following statements are true. Which one is most important in leading to the tremendous tidal heating that occurs on Io? [Hint]
    • A. 

      Io orbits Jupiter in the Io torus, and therefore has a surface that is bombarded by many charged particles.

    • B. 

      Io exhibits synchronous rotation, meaning that its rotation period and orbital period are the same.

    • C. 

      Io is the closest to Jupiter of Jupiter's large moons.

    • D. 

      Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites.

  • 276. 
    Which of the following is NOT a piece of evidence supporting the idea that Europa may have a subsurface ocean? [Hint]
    • A. 

      Europa's surface shows very few impact craters.

    • B. 

      Studies of Europa's magnetic field support the existence of a liquid water ocean.

    • C. 

      Astronomers have detected small lakes of liquid water on Europa's surface.

    • D. 

      Photos of Europa's surface show regions that appear to consist of jumbled icebergs frozen in place.

  • 277. 
    Based on our understanding of Titan as discussed in the text, which of the following is unlikely to be found on Titan? [Hint]
    • A. 

      Rain or snow consisting of ethane droplets or ice crystals

    • B. 

      A surface pressure higher than the atmospheric pressure on Earth

    • C. 

      Lakes of liquid ethane and methane

    • D. 

      Lakes of liquid water in the warmer equatorial regions

  • 278. 
    • A. 

      Triton appears to be made mostly of ice.

    • B. 

      Triton is too large to have been formed in the "miniature solar nebula" thought to have surrounded Neptune in its very early history.

    • C. 

      Triton orbits Neptune in a direction opposite that of Neptune's rotation.

    • D. 

      Triton is very small and potato-shaped, which is common of captured moons.

  • 279. 
    Which statement about Saturn's rings is NOT true? [Hint]
    • A. 

      The rings must look much the same today as they did shortly after Saturn formed.

    • B. 

      Some features of the rings are shaped by small moons that actually orbit within the ring system.

    • C. 

      The large gap known as the Cassini Division is shaped by an orbital resonance with the moon Mimas, which orbits well outside the rings.

    • D. 

      The rings are so thin that they essentially disappear from view when seen edge-on.

  • 280. 
    According to current understanding, which of the following is required in order for a planet to have rings? [Hint]
    • A. 

      The planet must once have had a large moon that came too close to it, shattering the moon and creating the ring particles.

    • B. 

      The planet must have many small moons that orbit relatively close to the planet in its equatorial plane.

    • C. 

      The planet must be at least as massive as Saturn.

    • D. 

      The planet must orbit its star at a distance greater than Mars orbits the Sun.

  • 281. 
    Which statement is NOT true? [Hint]
    • A. 

      Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.

    • B. 

      Objects in the asteroid belt are made mostly of rock and metal.

    • C. 

      Objects in the Kuiper belt are made mostly of rock and metal.

    • D. 

      Objects in the Oort cloud are made mostly of ice.

  • 282. 
    A rock found on Earth that crashed down from space is called _________. [Hint]
    • A. 

      An asteroid

    • B. 

      A meteor

    • C. 

      A meteorite

    • D. 

      An impact

  • 283. 
    The asteroid belt is located _________. [Hint]
    • A. 

      Beyond the orbit of Neptune

    • B. 

      Between the orbits of Earth and Mars

    • C. 

      Between the orbits of Jupiter and Saturn

    • D. 

      Between the orbits of Mars and Jupiter

  • 284. 
    A typical meteor is created by a particle about the size of a _________. [Hint]
    • A. 

      Basketball

    • B. 

      Pea

    • C. 

      Baseball

    • D. 

      Car

  • 285. 
    • A. 

      A piece of rock that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago

    • B. 

      A meteorite that was discovered by primitive people

    • C. 

      A type of meteorite that is usually made mostly of high-density metals

    • D. 

      A meteorite that fell to Earth at least 4 billion years ago

  • 286. 
    • A. 

      Being a fragment from the surface of the Moon

    • B. 

      Being a fragment of a shattered asteroid

    • C. 

      Being a fragment from the surface of Mars

    • D. 

      Being a fragment from Comet Halley

  • 287. 
    Which statement is NOT thought to be true of all comets? [Hint]
    • A. 

      All comets orbit the Sun.

    • B. 

      All comets are icy in composition.

    • C. 

      Comets are always followed by long tails.

    • D. 

      All comets are leftover planetesimals that originally condensed beyond the frost line in the solar nebula.

  • 288. 
    Which direction do a comet's dust and plasma tails point? [Hint]
    • A. 

      Perpendicular to the ecliptic plane

    • B. 

      Straight behind the comet in its orbit

    • C. 

      Generally away from the Sun

    • D. 

      Always almost due north

  • 289. 
    • A. 

      The Oort core

    • B. 

      The plasma tail

    • C. 

      The nucleus

    • D. 

      The coma

  • 290. 
    The total number of comets orbiting the Sun is estimated to be about _________. [Hint]
    • A. 

      1,000

    • B. 

      A trillion

  • 291. 
    • A. 

      The largest known Kuiper belt comet

    • B. 

      Pluto's moon

    • C. 

      A captured moon of Neptune

    • D. 

      The largest known asteroid

  • 292. 
    According to current ideas, Pluto is best explained as _________. [Hint]
    • A. 

      A terrestrial planet that is surprisingly far from the Sun

    • B. 

      An escaped moon of Jupiter or Saturn

    • C. 

      A very small jovian planet

    • D. 

      One of the larger (if not the largest) Kuiper belt comets

  • 293. 
    • A. 

      The ninth impact witnessed by astronomers in modern times

    • B. 

      The impact that created the Moon's largest crater

    • C. 

      The impact thought to have wiped out the dinosaurs

    • D. 

      The impact of a fragmented comet on Jupiter, carefully observed by astronomers when it occurred in 1994

  • 294. 
    In the impact theory of the extinction of the dinosaurs some 65 million years ago, the dinosaurs died off largely because _________. [Hint]
    • A. 

      Of injuries suffered from direct hits of pieces of the asteroid or comet

    • B. 

      Radiation from iridium in the asteroid caused the dinosaurs to die of cancer

    • C. 

      The impact caused massive earthquakes worldwide

    • D. 

      Of global climate effects initiated by dust and smoke that entered the atmosphere after the impact

  • 295. 
    • A. 

      The extinction of any species of plant or animal is considered a mass extinction

    • B. 

      The extinction of large animals, such as dinosaurs

    • C. 

      The extinction of a large fraction of the world's plant and animal species occurring in a relatively short period of time

    • D. 

      An extinction caused by the impact of an asteroid or comet

  • 296. 
    • A. 

      It is no larger than a typical mountain on one of the terrestrial planets.

    • B. 

      It is about the size of a terrestrial planet.

    • C. 

      It is smaller than the terrestrial planets but larger than Pluto.

    • D. 

      It is about half the diameter of Pluto, the smallest planet.

  • 297. 
    If we could put all the asteroids together, their total mass would be _________. [Hint]
    • A. 

      Greater than the mass of Earth but less than the mass of Jupiter

    • B. 

      About the mass of Earth

    • C. 

      About the mass of Mercury

    • D. 

      Much less than the mass of any terrestrial planet

  • 298. 
    • A. 

      The temperature in this portion of the solar nebula was just right to prevent rock from sticking together.

    • B. 

      There was not enough material in this part of the solar nebula to form a planet.

    • C. 

      Gravitational tugs from Jupiter prevented material from collecting together to form a planet.

    • D. 

      There was too much rocky material to form a terrestrial planet, but not enough gaseous material to form a jovian planet.

  • 299. 
    Gaps in the asteroid belt (often called Kirkwood gaps) are caused by _________. [Hint]
    • A. 

      Tidal forces from Jupiter

    • B. 

      Tidal forces from the Sun

    • C. 

      The competing gravitational tugs of Mars and Jupiter

    • D. 

      Orbital resonances with Jupiter

  • 300. 
    • A. 

      A star that has suddenly shot across the sky

    • B. 

      Emission of visible light from a particle that has not yet entered Earth's atmosphere

    • C. 

      The glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere

    • D. 

      The flash that occurs when a speeding rock from space hits the ground

  • 301. 
    Suppose you find a meteorite made almost entirely of metal. According to current theory, which of the following statements must be true? [Hint]
    • A. 

      Your meteorite was blasted off the surface of Mars by an impact.

    • B. 

      Your meteorite is a fragment from the core of a large asteroid that had undergone differentiation and then was shattered by a collision.

    • C. 

      Your meteorite is a fragment of an object from the Kuiper belt.

    • D. 

      Radiometric dating will show the age of your meteorite to be 4.6 billion years.

  • 302. 
    Which of the following objects are probably NOT located in the same general region of the solar system in which they originally formed? [Hint]
    • A. 

      Pluto

    • B. 

      Kuiper belt comets

    • C. 

      Oort cloud comets

    • D. 

      Asteroids of the asteroid belt

  • 303. 
    Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different? [Hint]
    • A. 

      It would have only one tail instead of two.

    • B. 

      It would be much brighter in appearance.

    • C. 

      It would not have a nucleus.

    • D. 

      It would not have a coma.

  • 304. 
    Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude? [Hint]
    • A. 

      It came from the Kuiper belt.

    • B. 

      It came from the Oort cloud.

    • C. 

      It has been on its current orbit for only a very short time compared to the age of our solar system.

    • D. 

      It has a coma and tail during most of each orbit.

  • 305. 
    • A. 

      You should duck and run for cover to avoid being blasted on the head by a rock from space

    • B. 

      An Earth-approaching asteroid has recently come very close to our planet

    • C. 

      Earth is crossing the orbit of a comet

    • D. 

      The solar wind is unusually strong

  • 306. 
    • A. 

      Pluto is always much farther from the Sun than Neptune.

    • B. 

      Pluto orbits the Sun exactly two times for every three Neptune orbits, which ensures the two planets never come close together.

    • C. 

      Actually, a collision of the two is inevitable within the next billion years.

    • D. 

      Pluto's orbit never comes anywhere close to Neptune's orbit.

  • 307. 
    • A. 

      They have the same basic composition.

    • B. 

      Both probably formed as a result of giant impacts.

    • C. 

      The same average density.

    • D. 

      They have the same approximate mass.

  • 308. 
    Which of the following is NOT a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt? [Hint]
    • A. 

      Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.

    • B. 

      Pluto's orbit is very similar to the orbits of other known Kuiper belt comets.

    • C. 

      Triton, which must once have orbited the Sun before being captured by Neptune, is larger than Pluto.

    • D. 

      Pluto's composition appears to match that of other known Kuiper belt comets.

  • 309. 
    Fossil evidence suggests a mass extinction occurring 65 million years ago. Which of the following is NOT a piece of evidence supporting the idea that an impact caused this mass extinction? [Hint]
    • A. 

      Unusually large abundances of iridium and other rare metals in a layer of clay that dates to 65 million years ago.

    • B. 

      An impact crater along the coast of Mexico that dates to 65 million years ago

    • C. 

      Grains of quartz that must have formed under very high temperature and pressure are found in a layer of clay that dates to 65 million years ago

    • D. 

      Fossilized dinosaur bones that contain fragments of rock that must have been shot out by the impact

  • 310. 
    On average, how often should an impactor strike the Earth with as much energy as that of a hydrogen bomb (like the Tunguska impact)? [Hint]
    • A. 

      Once every 10,000 years

    • B. 

      Once every 100 million years

    • C. 

      Once a century

    • D. 

      Once every million years

  • 311. 
    According to modern science, approximately how old is the Sun? [Hint]
    • A. 

      10,000 years

    • B. 

      4.6 billion years

    • C. 

      25 million years

    • D. 

      400 million years.

  • 312. 
    • A. 

      The Sun is made of atoms and molecules

    • B. 

      The Sun is made of material that acts like a liquid acts on Earth

    • C. 

      The Sun consists of gas in which many or most of the atoms are ionized (missing electrons)

    • D. 

      The Sun is roughly the same color as blood

  • 313. 
    Which of the following correctly describes how the process of gravitational contraction can make a star hot? [Hint]
    • A. 

      Gravitational contraction involves nuclear fusion, which generates a lot of heat.

    • B. 

      When a star contracts in size, gravitational potential energy is converted to thermal energy.

    • C. 

      Heat is generated when gravity contracts, because gravity is an inverse square law force.

    • D. 

      Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal.

  • 314. 
    • A. 

      The gravitational force and outward pressure

    • B. 

      The strong force and the electromagnetic force

    • C. 

      The strong force and the weak force

    • D. 

      The gravitational force and surface tension

  • 315. 
    The source of energy that keeps the Sun shining today is _________. [Hint]
    • A. 

      Gravitational contraction

    • B. 

      Chemical reactions

    • C. 

      Nuclear fission

    • D. 

      Nuclear fusion

  • 316. 
    • A. 

      100% hydrogen and helium

    • B. 

      50% hydrogen, 25% helium, 25% other elements

    • C. 

      90% dark matter, 10% ordinary matter

    • D. 

      70% hydrogen, 28% helium, 2% other elements

  • 317. 
    From center outward, which of the following lists the "layers" of the Sun in the correct order? [Hint]
    • A. 

      Core, radiation zone, convection zone, photosphere, chromosphere, corona

    • B. 

      Core, corona, radiation zone, convection zone, photosphere, chromosphere

    • C. 

      Core, radiation zone, convection zone, corona, chromosphere, photosphere

    • D. 

      Core, convection zone, radiation zone, corona, chromosphere, photosphere

  • 318. 
    • A. 

      Watts

    • B. 

      Joules

    • C. 

      Newtons

    • D. 

      Kilograms

  • 319. 
    The Sun's surface, as we see it with our eyes, is called the _________. [Hint]
    • A. 

      Core

    • B. 

      Photosphere

    • C. 

      Corona

    • D. 

      Chromosphere

  • 320. 
    • A. 

      It is the strong winds that blow across the surface of the Sun, causing sunspots to move around randomly.

    • B. 

      It is the wind that causes huge arcs of gas to rise above the Sun's surface, sometimes staying aloft for weeks.

    • C. 

      It is the name we give to the gas (or plasma) particles flowing outward from the surface of the Sun into the solar system.

    • D. 

      It is the uppermost layer of the Sun, lying just above the corona.

  • 321. 
    The fundamental nuclear reaction occurring in the core of the Sun is _________. [Hint]
    • A. 

      Nuclear fusion of helium to carbon

    • B. 

      Radioactive decay

    • C. 

      Nuclear fusion of hydrogen to helium

    • D. 

      Nuclear fission

  • 322. 
    • A. 

      It is the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.

    • B. 

      It is another name for the force that holds protons together in atomic nuclei.

    • C. 

      It is an alternative way of generating energy by nuclear fusion besides fusing hydrogen into helium.

    • D. 

      It describes the linkage between protons into long chains that occurs when temperatures are very high.

  • 323. 
    • A. 

      They have no mass.

    • B. 

      They are extremely rare.

    • C. 

      No one knows: this is the essence of the "solar neutrino problem."

    • D. 

      They have a tendency to pass through just about any material without any interactions.

  • 324. 
    To estimate the central temperature of the Sun, scientists _________. [Hint]
    • A. 

      Send probes to measure the temperature

    • B. 

      Monitor changes in Earth's atmosphere

    • C. 

      Use computer models to predict interior conditions

    • D. 

      Create a version of the Sun in a laboratory

  • 325. 
    Which statement best describes the solar neutrino problem? [Hint]
    • A. 

      No one understands how it can be possible for neutrinos to be produced in the Sun.

    • B. 

      It refers to the fact that neutrinos are extremely difficult to detect.

    • C. 

      Our current understanding of fusion in the Sun suggests that all neutrinos should be destroyed before they arrive at the Earth, yet neutrinos are being detected.

    • D. 

      Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected.

  • 326. 
    The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about _________. [Hint]
    • A. 

      One thousand years ago

    • B. 

      One hundred years ago

    • C. 

      A few hundred thousand years ago

    • D. 

      Three days ago

  • 327. 
    • A. 

      Energy is produced in the convection zone by thermal radiation.

    • B. 

      Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.

    • C. 

      Energy is produced in the convection zone by nuclear fusion.

    • D. 

      Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.

  • 328. 
    • A. 

      They are all shaped by the solar wind.

    • B. 

      They are all strongly influenced by magnetic fields on the Sun.

    • C. 

      They all occur only in the Sun's photosphere.

    • D. 

      They all have about the same temperature.

  • 329. 
    Which of the following is NOT a characteristic of the 11-year sunspot cycle? [Hint]
    • A. 

      The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.

    • B. 

      The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.

    • C. 

      The Sun's entire magnetic field flip-flops at the end of each cycle (at solar minimum).

    • D. 

      The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.

  • 330. 
    • A. 

      The sunspot cycle strongly influences Earth's weather.

    • B. 

      The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth.

    • C. 

      The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.

    • D. 

      Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.

  • 331. 
    In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea? [Hint]
    • A. 

      It predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size.

    • B. 

      It predicted that Earth would also shrink in size with time, which would make it impossible to have stable geology on our planet.

    • C. 

      It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

    • D. 

      It is physically impossible to generate heat simply by making a star shrink in size.

  • 332. 
    • A. 

      It is important during periods when the Sun is going from solar maximum to solar minimum.

    • B. 

      It is the primary energy generation mechanism in the Sun today.

    • C. 

      It has played a role throughout the Sun's history, but it was most important right after nuclear fusion began in the Sun's core.

    • D. 

      It was important when the Sun was forming from a shrinking interstellar cloud of gas.

  • 333. 
    • A. 

      The Sun maintains a steady temperature.

    • B. 

      The Sun always has the same amount of mass, creating the same gravitational force.

    • C. 

      The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.

    • D. 

      There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.

  • 334. 
    Which of the following is the best answer to the question "Why does the Sun shine?" [Hint]
    • A. 

      The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.

    • B. 

      As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.

    • C. 

      The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.

    • D. 

      As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.

  • 335. 
    • A. 

      The Sun's mass is about 300 times the mass of the Earth.

    • B. 

      The Sun's mass is about 300,000 times the mass of the Earth.

    • C. 

      The Sun's mass is about 30 times the mass of the Earth.

    • D. 

      Both have approximately the same mass.

  • 336. 
    The Sun's average surface (photosphere) temperature is about _________. [Hint]
    • A. 

      5,800 K

    • B. 

      37,000 K

    • C. 

      1,000,000 K

    • D. 

      1,000 K

  • 337. 
    Which of the following best describes why the Sun emits most of its energy in the form of visible light? [Hint]
    • A. 

      The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.

    • B. 

      Nuclear fusion in the Sun's core produces visible light photons.

    • C. 

      The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.

    • D. 

      Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.

  • 338. 
    The Sun's surface seethes and churns with a bubbling pattern. Why? [Hint]
    • A. 

      The churning is an illusion created by varying radiation, as the gas on the Sun's surface is actually quite still.

    • B. 

      The Sun's surface is boiling.

    • C. 

      The churning gas is being stirred up by the strong solar wind.

    • D. 

      We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.

  • 339. 
    Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants? [Hint]
    • A. 

      Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium.

    • B. 

      The Sun generates energy through fission while nuclear power plants generate energy through fusion.

    • C. 

      The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

    • D. 

      The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions.

  • 340. 
    Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together? [Hint]
    • A. 

      Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are very close together.

    • B. 

      Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together.

    • C. 

      Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

    • D. 

      Fusion can proceed only by the proton-proton chain, and therefore requires that protons come close enough together to be linked up into a chain.

  • 341. 
    The overall result of the proton-proton chain is _________. [Hint]
    • A. 

      4 H + 1 He + energy

    • B. 

      Individual protons are joined into long chains of protons

    • C. 

      P + p + 2H + energy

    • D. 

      6 H + 1 He + energy

  • 342. 
    Every second, the Sun converts 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons _________. [Hint]
    • A. 

      Are converted to an amount of energy equal to 4 million tons times the speed of light squared

    • B. 

      Are ejected into space in a solar wind

    • C. 

      Are reabsorbed as molecular hydrogen

    • D. 

      Are ejected into space by solar flares

  • 343. 
    Suppose that, for some unknown reason, the core of the Sun suddenly became hotter and the rate of nuclear fusion thereby increased. What would happen next? [Hint]
    • A. 

      The Sun would quickly run out of hydrogen, causing the temperature to return to its original value.

    • B. 

      The core would expand, reducing the pressure and temperature, and the rate of fusion would decrease until it returned to its original level.

    • C. 

      The rate of fusion would almost instantly skyrocket, causing the Sun to explode.

    • D. 

      The temperature would continue to increase, causing higher and higher fusion rates.

  • 344. 
    • A. 

      They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.

    • B. 

      They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

    • C. 

      They are too cold to emit any visible light.

    • D. 

      They are extremely hot and emit all their radiation as X rays rather than visible light.

  • 345. 
    • A. 

      Fusion in the Sun's core creates neutrinos as a byproduct.

    • B. 

      Solar flares create neutrinos with magnetic fields.

    • C. 

      The Sun does not emit neutrinos.

    • D. 

      Convection releases neutrinos, which random walk through the radiation zone.

  • 346. 
    Which of the following best describes the current status of our understanding of the solar neutrino problem? [Hint]
    • A. 

      Recent evidence suggests that the solar neutrino problem really was not a problem at all, and only seemed to be a problem because experimental data were being misinterpreted.

    • B. 

      Experimental evidence suggests that solar neutrinos can change from electron neutrinos to other types of neutrinos during their journey to Earth. If confirmed, the solar neutrino problem appears to be solved.

    • C. 

      The solar neutrino problem remains as perplexing as ever, and indeed makes everything we think we know about stars suspect.

    • D. 

      We have learned that the Sun's interior undergoes fusion at a far lower rate than we had expected, and that is why we had observed fewer neutrinos than expected.

  • 347. 
    • A. 

      The chromosphere is best observed with infrared telescopes and the corona is best observed with ultraviolet telescopes.

    • B. 

      The chromosphere and corona are both best studied with radio telescopes.

    • C. 

      The chromosphere and corona are both best studied with visible light.

    • D. 

      The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

  • 348. 
    The intricate patterns visible in an X-ray image of the Sun generally show _________. [Hint]
    • A. 

      Helioseismological fluctuations

    • B. 

      Granulation on the photosphere

    • C. 

      Extremely hot plasma flowing along magnetic field lines

    • D. 

      Structure within sunspots

  • 349. 
    • A. 

      We measure the magnetic field strength by observing the sizes of sunspots: bigger sunspots mean a stronger field.

    • B. 

      Magnetic fields can cause some spectral lines to split, so we can measure the Sun's magnetic field strength by carefully studying lines in the Sun's spectrum.

    • C. 

      Careful observations of auroras here on Earth allow us to determine the strength of the Sun's magnetic field.

    • D. 

      The Sun's magnetic field strength must be calculated using sophisticated computer models, because there are no direct ways of measuring it through observations of the Sun.

  • 350. 
    Satellites in low-Earth orbits are more likely to crash to Earth during the solar maximum periods of the sunspot cycle because _________. [Hint]
    • A. 

      They are more likely to have their electronics "fried" by a solar flare during solar maximum, and this will cause them to crash to Earth

    • B. 

      Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits

    • C. 

      Of increased magnetic interference

    • D. 

      It is too dangerous to send the Space Shuttle to service satellites during solar maximum

  • 351. 
    • A. 

      98% hydrogen, 2% helium

    • B. 

      Three quarters hydrogen, one quarter helium, no more than 2% heavier elements

    • C. 

      Half hydrogen and half helium

    • D. 

      95% hydrogen, 4% helium, no more than 1% heavier elements

  • 352. 
    The total amount of power (in watts, for example) that a star radiates into space is called its _________. [Hint]
    • A. 

      Luminosity

    • B. 

      Absolute magnitude

    • C. 

      Apparent brightness

    • D. 

      Flux

  • 353. 
    According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us doubles? [Hint]
    • A. 

      Its apparent brightness will decrease by a factor of 2.

    • B. 

      Its apparent brightness will increase by a factor of 4.

    • C. 

      Its apparent brightness will increase by a factor of 2.

    • D. 

      Its apparent brightness will decrease by a factor of 4.

  • 354. 
    Assuming that we can always measure the apparent brightness of a star, what does the inverse square law for light allow us to do? [Hint]
    • A. 

      It allows us to determine both distance and luminosity from the apparent brightness.

    • B. 

      It allows us to calculate a star's surface temperature if we know either its luminosity or its distance.

    • C. 

      It allows us to determine the distance to a star from its apparent brightness.

    • D. 

      It allows us to calculate a star's luminosity if we know its distance, or calculate its distance if we know its luminosity.

  • 355. 
    If star A is closer to us than star B, then Star A's parallax angle is _________. [Hint]
    • A. 

      Hotter than that of Star B

    • B. 

      Smaller than that of Star B

    • C. 

      Larger than that of Star B

    • D. 

      Fewer parsecs than that of Star B

  • 356. 
    Ten parsecs is about _________. [Hint]
    • A. 

      10 parallax seconds of angle

    • B. 

      150 million kilometers

    • C. 

      10,000 seconds

    • D. 

      32.6 light-years

  • 357. 
    If star A has an apparent magnitude of 3 and star B has an apparent magnitude of 5, which star is brighter in our sky? [Hint]
    • A. 

      Star A

    • B. 

      Star B

    • C. 

      The two stars have the same brightness in our sky, but Star A is closer to us than Star B.

    • D. 

      There is not enough information to answer the question.

  • 358. 
    From hottest to coolest, the order of the spectral types of stars is _________. [Hint]
    • A. 

      OBAFGKM

    • B. 

      OMKGFBA

    • C. 

      ABCDEFG

    • D. 

      OBAGFKM

    • E. 

      ABFGKMO

  • 359. 
    Our Sun is a star of spectral type _________. [Hint]
    • A. 

      S

    • B. 

      G

    • C. 

      F

    • D. 

      M

  • 360. 
    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? [Hint]
    • A. 

      We know the star's luminosity and distance.

    • B. 

      The star is a member of a binary star system.

    • C. 

      The star is of spectral type G.

    • D. 

      The star is of spectral type A.

  • 361. 
    Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts? [Hint]
    • A. 

      Eclipsing binary

    • B. 

      Spectroscopic binary

    • C. 

      Visual binary

    • D. 

      Double star

  • 362. 
    The axes on a Hertzsprung-Russell (H-R) diagram represent _________. [Hint]
    • A. 

      Mass and radius

    • B. 

      Luminosity and surface temperature

    • C. 

      Luminosity and apparent brightness

    • D. 

      Mass and luminosity

  • 363. 
    • A. 

      Its radius

    • B. 

      Its mass

    • C. 

      Its surface temperature

    • D. 

      Its age in years

  • 364. 
    On an H-R diagram, stellar radii _________. [Hint]
    • A. 

      Increase diagonally from the lower left to the upper right

    • B. 

      Are greatest in the lower left and least in the upper right

    • C. 

      Decrease from left to right

    • D. 

      Are impossible to determine

  • 365. 
    On an H-R diagram, stellar masses _________. [Hint]
    • A. 

      Decrease from left to right

    • B. 

      Can be determined from a star's position in the diagram only for main sequence stars, and decrease from upper left to lower right

    • C. 

      Are impossible to determine

    • D. 

      Are greatest in the lower left and least in the upper right

  • 366. 
    • A. 

      More massive stars live considerably longer lives than less massive stars.

    • B. 

      More massive stars live slightly longer lives than less massive stars.

    • C. 

      More massive stars live slightly shorter lives than less massive stars.

    • D. 

      More massive stars live considerably shorter lives than less massive stars.

  • 367. 
    Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant? [Hint]
    • A. 

      Spectral type O9, luminosity class I

    • B. 

      Spectral type M1, luminosity class V

    • C. 

      Spectral type G2, luminosity class V

    • D. 

      Spectral type M2, luminosity class I

  • 368. 
    • A. 

      They generate energy through hydrogen fusion in their core.

    • B. 

      They are all spectral type G.

    • C. 

      They all have approximately the same mass.

    • D. 

      They are in the final stage of their lives.

  • 369. 
    Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true? [Hint]
    • A. 

      Earth would fly off into interstellar space.

    • B. 

      The supergiant's surface temperature would be much hotter than the surface temperature of our Sun.

    • C. 

      The supergiant would appear as large as the full Moon in our sky.

    • D. 

      Earth would be inside the supergiant.

  • 370. 
    • A. 

      It is a main sequence star of spectral type F, which tends to look white in color.

    • B. 

      It is the remains of a star, composed mostly of carbon, that no longer produces energy by nuclear fusion.

    • C. 

      It is a star that follows a period-luminosity relation.

    • D. 

      It is a type of star that produces energy by gravitational contraction.

  • 371. 
    Which of the following statements comparing open and globular star clusters is NOT true? [Hint]
    • A. 

      Open and globular clusters each typically contain a few hundred stars.

    • B. 

      Open clusters are found only in the disk of the galaxy while globular clusters may be found both in the disk and the halo of the galaxy.

    • C. 

      Stars in open clusters are relatively young while stars in globular clusters are very old.

    • D. 

      For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age.

  • 372. 
    • A. 

      It is the spectral type of the hottest main sequence star in a star cluster, and it tells us the cluster's age.

    • B. 

      It is the point in a star cluster beyond which main sequence stars are not found, and it tells us the cluster's distance.

    • C. 

      It is the luminosity class of the largest star in a star cluster, and it tells us the cluster's age.

    • D. 

      It is the mass of the most massive star in the star cluster, and it tells us the cluster's size.

  • 373. 
    All stars are born with the same basic composition, yet stars can look quite different from one another. Which two factors primarily determine the innate characteristics of a star? [Hint]
    • A. 

      Its mass and its stage of life

    • B. 

      Its age and its location in the galaxy

    • C. 

      Its apparent brightness and its distance

    • D. 

      Its apparent brightness and its luminosity

    • E. 

      Its mass and its surface temperature

  • 374. 
    Based on the definition of apparent brightness, which units are appropriate for its measurement? [Hint]
    • A. 

      Watts

    • B. 

      Watts per square meter

    • C. 

      Joules

    • D. 

      Newtons

  • 375. 
    Suppose two stars are identical except that one is twice as far away from us as the other. Which statement is true? [Hint]
    • A. 

      Both stars have the same luminosity, but the apparent brightness of the closer star is four times as great as that of the more distant star.

    • B. 

      Both stars have the same luminosity, but the apparent brightness of the more distant star is four times as great as that of the closer star.

    • C. 

      Both stars have the same luminosity, but the apparent brightness of the closer star is twice as great as that of the more distant star.

    • D. 

      Both stars have the same apparent brightness, but the luminosity of the closer star is four times as great as that of the more distant star.

  • 376. 
    Suppose that a star has a parallax angle of 1/20 arcsecond. If so, it is _________. [Hint]
    • A. 

      20 light-years away

    • B. 

      20 parsecs away

    • C. 

      1/20 parsec away

    • D. 

      10 parsecs away

  • 377. 
    Which of the following statements about spectral types of stars is NOT generally true? [Hint]
    • A. 

      The spectral type of a star can be used to determine its distance.

    • B. 

      The spectral type of a star can be determined by identifying lines in its spectrum.

    • C. 

      The spectral type of a star can be used to determine its color.

    • D. 

      The spectral type of a star can be used to determine its surface temperature.

  • 378. 
    • A. 

      Sirius has a higher core temperature than Rigel.

    • B. 

      Sirius has a higher surface temperature than Rigel.

    • C. 

      Rigel has a higher core temperature than Sirius.

    • D. 

      Rigel has a higher surface temperature than Sirius.

  • 379. 
    Astronomers generally can measure a star's mass only if it is a member of a binary star system. What characteristics of the stars must we know to measure the masses of the stars in a binary system? [Hint]
    • A. 

      Their luminosities and distance from Earth

    • B. 

      Their spectral types and their distance from Earth

    • C. 

      Their absolute magnitudes and their luminosities

    • D. 

      Their orbital period and average orbital distance

  • 380. 
    Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The most likely explanation is that _________. [Hint]
    • A. 

      The star is a Cepheid variable

    • B. 

      The star is a white dwarf

    • C. 

      The star is periodically ejecting gas into space, every 73 hours

    • D. 

      The star is a member of an eclipsing binary star system

  • 381. 
    To answer this question, refer to the labels (a) through (e) on the following sketch of an H-R diagram. [Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choices (c) or (d) offer better answers to the question than (a), use the best choice.] Which group represents stars that are cool and dim? [Hint]
    • A. 

      A

    • B. 

      B

    • C. 

      C

    • D. 

      D

    • E. 

      E

  • 382. 
    You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the _________. [Hint]
    • A. 

      Mass of the star

    • B. 

      Spectral type of the star

    • C. 

      Apparent brightness of the star in our sky

    • D. 

      Distance to the star

  • 383. 
    The approximate main-sequence lifetime of a star of spectral type O is _________. [Hint]
    • A. 

      10,000 years

    • B. 

      3 million years

    • C. 

      10 billion years

    • D. 

      300 million years

  • 384. 
    • A. 

      Astronomers discovered the relationship by measuring the masses of main-sequence stars in binary systems, and they assume that the same relationship holds for single stars as well.

    • B. 

      Astronomers understand the process of hydrogen fusion and stellar structure so well that they can predict the masses of main-sequence stars.

    • C. 

      The luminosity of any star, main sequence or not, tells us its mass.

    • D. 

      Astronomers have measured stellar radii of main-sequence stars in eclipsing binary systems when one star eclipses its companion; from the radii, astronomers can then calculate the mass of the main sequence star.

  • 385. 
    The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest? [Hint]
    • A. 

      The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.

    • B. 

      The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.

    • C. 

      The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.

    • D. 

      The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.

  • 386. 
    The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is most likely to be located in the halo of our galaxy? [Hint]
    • A. 

      The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.

    • B. 

      The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.

    • C. 

      The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.

    • D. 

      The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.