# Astronomy A Beginners Guide to the Universe 7th edition by Chaisson – Test Bank

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###### Astronomy A Beginners Guide to the Universe 7th edition by Chaisson – Test Bank

Chapter 2   Light and Matter: The Inner Workings of the Cosmos

1) Radio waves, visible light, and X-rays are all types of electromagnetic radiation.

Diff: 1

Section Ref.:  2.1

2) The frequency of a water wave gives us its height.

Diff: 1

Section Ref.:  2.1

3) If a new wave arrives on shore every two seconds, then its frequency is 2 Hz.

Diff: 2

Section Ref.:  2.1

4) The greater the disturbance of the medium, the higher the amplitude of the wave.

Diff: 2

Section Ref.:  2.1

5) While gravity is always attractive, electromagnetic forces are always repulsive.

Diff: 1

Section Ref.:  2.2

6) Changing the electric field will have no effect on the magnetic fields of a body.

Diff: 1

Section Ref.:  2.2

7) As they move through space, the vibrating electrical and magnetic fields of a light wave must move perpendicular to each other.

Diff: 1

Section Ref.:  2.2

8) Wave energy can only be transmitted through a material medium.

Diff: 2

Section Ref.:  2.2

9) As white light passes through a prism, the red (longer) wavelengths bend less than the blue (shorter) wavelengths, so forming the rainbow of colors.

Diff: 2

Section Ref.:  2.3

10) Observations in the X-ray portion of the spectrum are routinely done from the surface of the Earth.

Diff: 2

Section Ref.:  2.3

11) In blackbody radiation, the energy is radiated uniformly in every region of the spectrum, so the radiating body appears black in color.

Diff: 2

Section Ref.:  2.4

12) According to Wein’s law, the larger the blackbody, the shorter its peak wavelength.

Diff: 1

Section Ref.:  2.4

13) A blue star has a higher surface temperature than a red star.

Diff: 1

Section Ref.:  2.4

14) According to Wein’s law, the higher the surface temperature of a star, the redder its color.

Diff: 2

Section Ref.:  2.4

15) Doubling the temperature of a blackbody will double the total energy it radiates.

Diff: 2

Section Ref.:  2.4

16) As a star’s temperature increases, the frequency of peak emission also increases.

Diff: 2

Section Ref.:  2.4

17) The spectral lines of each element are distinctive to that element, whether we are looking at emission or absorption lines.

Diff: 1

Section Ref.:  2.5

18) An absorption line spectrum, with dark lines crossing the rainbow of the continuum, is produced by a low-density hot gas.

Diff: 2

Section Ref.:  2.5

19) An emission line results from an electron falling from a higher to lower energy orbital around its atomic nucleus.

Diff: 1

Section Ref.:  2.6

20) The shorter a wave’s wavelength, the greater its energy.

Diff: 1

Section Ref.:  2.6

21) Spectral lines are produced when an electron makes a transition from one energy state to another.

Diff: 1

Section Ref.:  2.6

22) In the Bohr model of the atom, an electron can only exist in specific, well-defined energy levels.

Diff: 2

Section Ref.:  2.6

23) When an electron in a hydrogen atom drops from the second to the first excited energy state it emits a bright red emission line called hydrogen alpha.

Diff: 2

Section Ref.:  2.6

24) The Zeeman effect reveals the presence of strong magnetic fields by the splitting of spectral lines.

Diff: 2

Section Ref.:  2.8

25) The broader the spectral line, the higher the pressure of the gas that is creating it.

Diff: 2

Section Ref.:  2.8

26) In the Doppler effect, a red shift of spectral lines shows us the source is receding from us.

Diff: 1

Section Ref.:  2.7

27) The larger the red shift, the faster the distant galaxy is rushing toward us.

Diff: 1

Section Ref.:  2.7

28) If a fire truck’s siren is rising in pitch, it must be approaching us.

Diff: 1

Section Ref.:  2.7

29) You would perceive a change in a visible light wave’s amplitude as a change in its color.

Diff: 1

Section Ref.:  2.3

30) Spectroscopy of a star can reveal its temperature, composition, and line-of-sight motion.

Diff: 1

Section Ref.:  2.8

31) The Doppler effect can reveal the rotation speed of a star by the splitting of the spectral lines.

Diff: 2

Section Ref.:  2.8

32) Which of these is not a form of electromagnetic radiation?

1. A) DC current from your car battery
2. B) light from your camp fire
3. C) X-rays in the doctor’s office
4. D) ultraviolet causing a suntan

Diff: 1

Section Ref.:  2.1

33) A wave’s velocity is the product of the

1. A) frequency times the period of the wave.
2. B) period times the energy of the wave.
3. C) amplitude times the frequency of the wave.
4. D) frequency times the wavelength of the wave.
5. E) amplitude times the wavelength of the wave.

Diff: 1

Section Ref.:  2.1

34) Consider this diagram. Which statement is true?

1. A) The amplitude is 4 and the wavelength is 6.
2. B) The amplitude is 6 and the wavelength is 4.
3. C) The amplitude is 8 and the wavelength is 6.
4. D) The amplitude is 4 and the wavelength is 12.
5. E) The amplitude is 8 and the wavelength is 12.

Diff: 2

Section Ref.:  2.1

35) If a wave’s frequency doubles and its speed stays constant, its wavelength

1. A) is halved.
2. B) is also doubled.
3. C) is unchanged, as c is constant.
4. D) is now 4× longer.
5. E) becomes 16× longer.

Diff: 2

Section Ref.:  2.1

36) The speed of light in a vacuum is

1. A) 300,000 km/sec.
2. B) 768 km/hour.
3. C) 186,000 miles per hour.
4. D) h = E/c.
5. E) not given.

Diff: 1

Section Ref.:  2.2

37) Which of these is the same for all forms of electromagnetic (E-M) radiation in a vacuum?

1. A) amplitude
2. B) wavelength
3. C) frequency
4. D) speed
5. E) photon energy

Diff: 1

Section Ref.:  2.3

38) The two forms of electromagnetic (E-M) radiation that experience the least atmospheric opacity are

1. A) visible light and radio waves.
2. B) visible light and infrared waves.
3. C) microwaves and radio waves.
4. D) X and gamma radiation.
5. E) ultraviolet and infrared waves.

Diff: 2

Section Ref.:  2.3

39) The radiation our eyes are most sensitive to is the color

1. A) red at 6563 Angstroms.
2. B) yellow-green at about 550 nm.
3. C) violet at 7,000 Angstroms.
4. D) blue at 4,321 nm.
5. E) black at 227 nm.

Diff: 2

Section Ref.:  2.3

40) Medium A blocks more of a certain wavelength of radiation than medium B. Medium A has a higher

1. A) transparency.
2. B) seeing.
3. C) clarity.
4. D) opacity.
5. E) albedo.

Diff: 2

Section Ref.:  2.3

41) In the Kelvin scale, absolute zero lies at

1. A) zero K.
2. B) 273 degrees C
3. C) -373 degrees C.
4. D) Both A and B are correct.
5. E) Both A and C are correct.

Diff: 1

Section Ref.:  2.4

42) What is true of a blackbody?

1. A) It appears black to us, regardless of its temperature.
2. B) Its energy is not a continuum.
3. C) Its energy peaks at the wavelength determined by its temperature.
4. D) If its temperature doubled, the peak in its radiation curve would be doubled in wavelength.
5. E) It has a complete absence of thermal energy.

Diff: 1

Section Ref.:  2.4

43) What is the name of the temperature scale that places zero at the point where all atomic and molecular motion ceases?

1. A) Fahrenheit
2. B) Celsius
3. C) Kelvin
5. E) Ransom

Diff: 2

Section Ref.:  2.4

44) The total energy radiated by a blackbody depends on

1. A) the fourth power of its temperature.
2. B) the square of its temperature.
3. C) the square root of its temperature.
4. D) the fourth root of its temperature.
5. E) the cube of its temperature.

Diff: 2

Section Ref.:  2.4

45) Increasing the temperature of a blackbody by a factor of 3 will increase its energy by a factor of

1. A) 3
2. B) 6
3. C) 9
4. D) 12
5. E) 81

Diff: 3

Section Ref.:  2.4

46) If a star was the same size as our Sun, but was 81times more luminous, it must be

1. A) twice as hot as our Sun.
2. B) three times hotter than the Sun.
3. C) four times hotter than the Sun.
4. D) nine times hotter than the Sun.
5. E) 81 times hotter than the Sun.

Diff: 3

Section Ref.:  2.4

47) The Sun’s observed spectrum is

1. A) a continuum with no lines, as shown by the rainbow.
2. B) a continuum with emission lines.
3. C) only absorption lines on a black background.
4. D) a continuum with absorption lines.
5. E) only emission lines on a black background.

Diff: 1

Section Ref.:  2.5

48) The element first found in the Sun’s spectrum, then on Earth 30 years later, is

1. A) hydrogen.
2. B) helium
3. C) solarium.
4. D) technicum.
5. E) aluminum.

Diff: 2

Section Ref.:  2.5

49) A jar filled with gas is placed directly in front of a second jar filled with gas. Using a spectroscope to look at one jar through the other you observe dark spectral lines. The jar closest to you contains

1. A) the hotter gas.
2. B) the cooler gas.
3. C) gas at the same temperature as the other jar.
4. D) the exact same gas as the other jar.
5. E) gas at very high pressure.

Diff: 3

Section Ref.:  2.5

50) Which of these is emitted when an electron falls from a higher to lower orbital?

1. A) another electron
2. B) a positron
3. C) a neutrino
4. D) a photon
5. E) a graviton

Diff: 2

Section Ref.:  2.6

51) In Bohr’s model of the atom, electrons

1. A) only make transitions between orbits of specific energies.
2. B) are not confined to specific orbits.
3. C) are spread uniformly through a large, positive mass.
4. D) can be halfway between orbits.
5. E) move from one orbit to the next orbit in many small steps.

Diff: 2

Section Ref.:  2.6

52) In general, the spectral lines of molecules are

1. A) more complex than those of atoms.
2. B) the same as the atoms they contain.
3. C) only absorption lines.
4. D) less complex than those of atoms.
5. E) nonexistent.

Diff: 2

Section Ref.:  2.6

1. A) can only travel in a dense medium.
2. B) has only the properties of waves.
3. C) can behave both as a wave and as a particle.
4. D) is the same as a sound wave.
5. E) has nothing in common with radio waves.

Diff: 2

Section Ref.:  2.6

54) In a hydrogen atom, a transition from the 2nd to the 1st excited state will produce

1. A) the bright red Balmer alpha emission line.
2. B) no emission line.
3. C) a dark absorption line.
4. D) an ultraviolet spectral line.
5. E) three different emission lines.

Diff: 3

Section Ref.:  2.6

55) For hydrogen, the transition from the first to third excited state produces

1. A) a red emission line.
2. B) a blue green absorption line.
3. C) a violet emission line.
4. D) an infrared line.
5. E) an ultraviolet line.

Diff: 3

Section Ref.:  2.6

56) The observed spectral lines of a star are all shifted towards the red end of the spectrum. Which statement is true?

1. A) This is an example of the photoelectric effect.
2. B) This is an example of the Doppler effect.
3. C) The second law of Kirchhoff explains this.
4. D) The star is not rotating.
5. E) The star has a radial velocity towards us.

Diff: 2

Section Ref.:  2.7

57) If a source of light is approaching us at 3,000 km/sec, then all its waves are

1. A) blue shifted by 1%.
2. B) red shifted by 1%.
3. C) not affected, as c is constant regardless of the direction of motion.
4. D) blue shifted out of the visible spectrum into the ultraviolet.
5. E) red shifted out of the visible into the infrared.

Diff: 2

Section Ref.:  2.7

58) If the rest wavelength of a certain line is 600 nm, but we observe it at 594 nm, then

1. A) the source is approaching us at 1 % of the speed of light.
2. B) the source is approaching us at 0.1 % of the speed of light.
3. C) the source is receding from us at 10% of the speed of light.
4. D) the source is getting 1% hotter as we watch.
5. E) the source is spinning very rapidly, at 1% of the speed of light.

Diff: 2

Section Ref.:  2.7

59) According to the Zeeman effect, the splitting of a sunspot’s spectral lines is due to

1. A) their rapid rotation.
2. B) temperature variations.
3. C) their magnetic fields.
5. E) a Doppler shift.

Diff: 2

Section Ref.:  2.8

60) The distance from a wave’s crest to its undisturbed position is the ________.

Diff: 1

Section Ref.:  2.1

61) The product of the wavelength times the frequency of a wave is its ________.

Diff: 1

Section Ref.:  2.1

62) A wave with a period of .01 seconds has a frequency of ________ Hz.

Diff: 2

Section Ref.:  2.1

63) A frequency of one hundred ________ means the wave is vibrating one hundred million times per second; this is a typical carrier frequency for FM (frequency modulation) radio.

Diff: 2

Section Ref.:  2.1

64) A wave with a frequency of 2 Hz will have a period of ________.

Answer:  one half second (0.5 s)

Diff: 2

Section Ref.:  2.1

65) An FM station broadcasts at a frequency of 100 MHz. The wavelength of its carrier wave is ________.

Diff: 3

Section Ref.:  2.1, 2.3

66) In electromagnetic waves, the electric and magnetic fields vibrate ________ to each other.

Diff: 2

Section Ref.:  2.2

67) A featureless spectrum, such as a rainbow, is said to be ________.

Diff: 1

Section Ref.:  2.4

68) Stars that appear blue or white in color are ________ than our yellow Sun.

Diff: 1

Section Ref.:  2.4

69) According to Wein’s law, the wavelength of the peak energy will be ________ if the temperature of the blackbody is doubled.

Diff: 1

Section Ref.:  2.4

70) The Sun’s blackbody curve peaks in the ________ portion of the spectrum.

Diff: 1

Section Ref.:  2.4

71) Knowing the peak emission wavelength of a blackbody allows you to determine its ________.

Diff: 2

Section Ref.:  2.4

72) Stefan’s law notes that total energy radiated is proportional to the ________ power of the temperature of the blackbody.

Diff: 2

Section Ref.:  2.4

73) A dense, hot body will give off a(n) ________ spectrum.

Diff: 1

Section Ref.:  2.5

74) Fraunhofer was the German astronomer who first noted ________ lines in the Sun’s spectrum.

Diff: 2

Section Ref.:  2.5

75) The common element with bright red, blue-green, and violet emission lines is ________.

Diff: 2

Section Ref.:  2.5

76) The common element discovered in the Sun’s spectrum before it was found here is ________.

Diff: 2

Section Ref.:  2.5

77) When an electron moves from a lower to a higher energy state, a photon is ________.

Diff: 1

Section Ref.:  2.6

78) An electron has a ________ electric charge.

Diff: 1

Section Ref.:  2.6

79) The most energetic photons are ________.

Diff: 2

Section Ref.:  2.6

80) The energy of the photon depends on its ________.

Diff: 2

Section Ref.:  2.6

81) Why can’t we be certain that the Andromeda Galaxy exists today?

Answer:  Since it lies 2.5 million light years distant, the most recent image we have is still 2.5 million years out of date, so we cannot prove it is still there. It probably is, though.

Diff: 2

Section Ref.:  2.1

82) How do sound and light waves differ?

Answer:  Sound waves travel much slower, and need a physical medium, such as air, to be transmitted. Light travels best in the vacuum of space.

Diff: 2

Section Ref.:  2.1

83) An AM station is broadcasting at 980 kHz, while an FM station up the road is assigned 98 MHz. How do their carrier waves compare?

Answer:  As the frequency of the FM station is 100 times higher than the AM station, the FM carrier wave must be 100 shorter in wavelength.

Diff: 3

Section Ref.:  2.1

84) No one can hear you scream (or fire a weapon) in space, regardless of the Hollywood special effects. Explain why.

Answer:  Sound waves must travel though a material medium, and cannot pass through a vacuum. The blast might be seen, but the boom will not be heard.

Diff: 1

Section Ref.:  2.2

85) What two regions of the electromagnetic spectrum are best utilized by ground-based astronomers, and why?

Diff: 2

Section Ref.:  2.3

86) How can you determine the distance to a spacecraft from the time it takes its radio signal to reach Earth?

Answer:  In a vacuum, all electromagnetic radiation, including radio waves, travel at the same speed: 300,000 km/s. Measuring the time it takes the radio signal to reach us and multiplying by 300,000 km/s gives the distance to the spacecraft.

Diff: 3

Section Ref.:  2.2

87) Newton found that when light passed through a prism, it was dispersed into the component colors. Which bent the least, and why?

Answer:  The red waves are bent less by the glass than are the other colors because they have the longest wavelength. Shorter wavelengths bend more than longer wavelengths.

Diff: 2

Section Ref.:  2.3

88) What do infrared and ultraviolet waves have in common? How do they differ?

Answer:  Both are forms of electromagnetic radiation, both travel at c in a vacuum, and both are largely absorbed by our atmosphere. They differ greatly in frequency, wavelength, and photon energy, however, with UV much more energetic than IR.

Diff: 2

Section Ref.:  2.3

89) What do gamma rays, X-rays, light, and radio waves all have in common?

Answer:  While they vary widely in wavelengths and frequencies, they are all forms of electromagnetic radiation and all travel at c, the speed of light, in a vacuum.

Diff: 2

Section Ref.:  2.3

90) How does human vision’s peak in color sensitivity relate to the Sun?

Answer:  Our eyes are tuned to utilize best the type of radiation our star produces the most of, and yellow lies in the middle of the visible spectrum.

Diff: 2

Section Ref.:  2.3

91) Give at least two advantages of the Kelvin temperature scale for astronomers.

Answer:  It is an absolute scale, so there are never any negative readings. Wein’s and Stefan’s laws are only mathematically correct if Kelvin temperatures are used.

Diff: 3

Section Ref.:  2.4

92) The Great Nebula in Orion, M-42, is a low-density cloud of hot gas. Use Kirchhoff’s laws to describe its spectrum.

Answer:  Kirchhoff’s second law notes that a hot thin gas will create an emission spectrum of bright lines through the spectroscope.

Diff: 2

Section Ref.:  2.5

93) According to Kirchhoff’s first law why do dense, hot bodies create the type of spectrum they do?

Answer:  Kirchhoff’s first law states that a dense, hot medium emits light of all wavelengths, creating a continuous spectrum.

Diff: 3

Section Ref.:  2.5

94) If the magnetic fields are very strong, such as around sunspots, how are spectral lines affected by the Zeeman effect?

Answer:  A strong magnetic field will cause the lines to appear split apart.

Diff: 3

Section Ref.:  2.6

95) State the relationship between frequency, photon energy, and wavelength.

Answer:  The higher the frequency, the greater the energy the photon carries, but the shorter its wavelength.

Diff: 2

Section Ref.:  2.3, 2.6

96) Explain how the Zeeman effect allows us to study stellar magnetic fields.

Answer:  The Zeeman effect causes spectral lines to appear split into two. This tells us magnetic fields are present. The greater the observed splitting, the stronger the magnetic fields are.

Diff: 3

Section Ref.:  2.8

97) Explain how Bohr’s model creates emission and absorption lines in the spectrum.

Answer:  Bohr’s model has the electron orbitals quantized into discrete energies. Each upward transition to a higher energy state produces an absorption line (energy is absorbed). Each downward transition produces an emission line (energy is emitted). The energy absorbed or emitted is exactly equal to the difference in energy levels.

Diff: 3

Section Ref.:  2.6

98) What information about a star can be inferred from its Doppler shift?

Answer:  The Doppler shift gives the star’s radial velocity, either towards or away from us.

Diff: 2

Section Ref.:  2.7

99) A binary star system is one with two stars orbiting each other. How can the Doppler Effect be used to find binary stars whose orbital plane is along our line of sight and determine their periods?

Answer:  As the two stars orbit each other rapidly, one will approach us, creating a blue shift of its spectral lines, while its retreating companion shows a red shift. The time to go through two splits and recombinations of their lines is their orbital period.

Diff: 3

Section Ref.:  2.7

100) Explain what types of information can be obtained from a line spectrum.

Answer:  The element which created it, the line-of-sight velocity of the source, its rotation speed, temperature, the pressure of the gas emitting the radiation, and even its magnetic field may also be found.

Diff: 2

Section Ref.:  2.8

101) If we increased the pressure in a gas, how will its spectral lines be affected?

Answer:  The lines will broaden (or even disappear if the density becomes too great)

Diff: 2

Section Ref.:  2.8

102) Contrast the speeds of sound and light in watching a flash of lightning, then listening for the thunder to follow.

Answer:  Light travels at 300,000 km/sec, so the flash of light is almost instantaneous from a few miles away; sound travels at about a fifth of a mile per second, so if the thunder follows the lightning by five seconds, the bolt hit about a mile away.

Diff: 3

Section Ref.:  2.2

103) How can Wein’s law be used to determine the temperature of a star?

Answer:  Careful analysis of the blackbody curve of the star’s entire radiation spectrum will reveal a peak that is unique to a given temperature. Basically, the bluer the star’s radiation, the hotter its surface will be.

Diff: 1

Section Ref.:  2.4

104) Why would a hotter star appear blue-white while a cooler star appear red or not be visible at all?

Answer:  Stefan’s law notes that the higher the temperature, the more luminous the body is, so such stars produce great amounts of visible light. The hotter the star the shorter the wavelength it peaks at. A star that emits light across the entire visible spectrum would appear white. One that peaked beyond the visible would appear blue-white. A cooler star may peak in the red part of the spectrum, or even in the infrared.

Diff: 2

Section Ref.:  2.4

105) How does Stefan’s law and a knowledge of Earth’s history tell us that the Sun’s temperature cannot have varied much in the last 3.5 billion years?

Answer:  Since even a small change in temperature, raised to the fourth power, would result in a large change in the total solar energy radiated, if the Sun had cooled much, our oceans would have frozen and life would have ceased to exist here.

Diff: 3

Section Ref.:  2.4

106) Explain the appearance of the Sun’s spectrum, as noted by Fraunhofer.

Answer:  The Sun is dense, and gives rise to a continuous spectrum, peaked in the color yellow as dictated by the 5800K temperature of its surface. Then the cooler, less dense gas above the surface absorbs some of the energy in transit, revealing its composition by the particular absorption lines we observe from Earth.

Diff: 3

Section Ref.:  2.5

107) How does the energy of a water wave differ from the energy of a photon?

Answer:  Amplitudes of sound (and water) waves can differ greatly and still have the same wavelength and frequency, as they are the result of the motions of large numbers of molecules. For photons, the energy is quantized, so that each photon of a given wavelength must carry the same amount of energy.

Diff: 3

Section Ref.:  2.5

108) Why do we know that the red Balmer emission line in hydrogen represents a smaller quantum leap than the violet line?

Answer:  Red light has a longer wavelength than violet light; therefore a red photon contains less energy than a violet one. Since the photon given off when an electron’s energy level changes has an energy equal to the energy difference between the two levels, the less energetic photon represents a smaller difference.

Diff: 3

Section Ref.:  2.6

109) Give an example of the Doppler Effect being used in a baseball game.

Answer:  The Doppler “gun” can focus on the motion of the baseball, and give us the speed that the pitcher is delivering it to the plate.

Diff: 1

Section Ref.:  2.7

110) Give and explain an example of the use of the Doppler Effect on the highway.

Answer:  The radar gun of a highway patrolman sends out a pulsed beam to be reflected back, thus giving the speed of your car and perhaps netting you a ticket.

Diff: 2

Section Ref.:  2.7

111) How can the Doppler Effect be used to determine if a storm is forming into a tornado?

Answer:  Radar can determine the distance to a storm cloud. Since a tornado rotates very rapidly, Doppler radar can measure the difference in velocity between the two sides of the storm to determine if it is rotating.

Diff: 3

Section Ref.:  2.7

112) Explain how the Doppler Effect has been used to detect invisible planets orbiting other Sun-like stars.

Answer:  The planets are massive enough to pull their star slightly off course as they orbit from one side to the other, producing a cycle of red and blue shifts that allow us to deduce that the planet is present, and how long it takes to orbit its star.

Diff: 3

Section Ref.:  2.7

Astronomy: A Beginner’s Guide to the Universe, 7e (Chaisson/McMillan)

Chapter 8   Moons, Rings, and Plutoids: Small Worlds Among Giants

1) Two of the Galilean moons of Jupiter are the size of Mercury, and the two others are about as big as our own Moon.

Diff: 1

Section Ref.:  8.1

2) Besides Mars, exobiologists find Europa also a good candidate for life.

Diff: 1

Section Ref.:  8.1

3) The surface of Io looks most like the pack ice of the Arctic Ocean of Earth.

Diff: 1

Section Ref.:  8.1

4) Io’s internal heat is due to tidal interactions with Jupiter and Europa.

Diff: 1

Section Ref.:  8.1

5) Like our Moon and most others, all four large Jovian satellites have one side constantly fixed toward Jupiter as they revolve and rotate.

Diff: 1

Section Ref.:  8.1

6) Like Jupiter’s other icy moons, Europa is covered with craters.

Diff: 1

Section Ref.:  8.1

7) The Cassini probe Huygens made a soft landing on Titan.

Diff: 1

Section Ref.:  8.1

8) All four of Jupiter’s big moons, like most moons in the solar system, revolve clockwise (retrograde) around their planet’s equator.

Diff: 2

Section Ref.:  8.1

9) While Ganymede and Callisto are about the same size, the surface of Callisto is much younger, with considerable tectonic reformation.

Diff: 2

Section Ref.:  8.1

10) Of all the Galilean satellites, the surface of Europa is the youngest in age.

Diff: 2

Section Ref.:  8.1

11) Io’s surface volcanism is driven by phase changes of sulfur and its compounds.

Diff: 2

Section Ref.:  8.1

12) Due to tidal stresses, it is likely most of Io is molten, with a relatively thin solid crust.

Diff: 2

Section Ref.:  8.1

13) The weak magnetic field of Europa may originate from a rapidly rotating liquid iron core.

Diff: 2

Section Ref.:  8.1

14) Ganymede is the largest satellite in the solar system.

Diff: 2

Section Ref.:  8.1

15) The processes which produced Ganymede’s groove terrain are on-going, according to the latest Galileo images.

Diff: 2

Section Ref.:  8.1

16) The large, dark mare on Ganymede were created by water that erupted from within the moon.

Diff: 2

Section Ref.:  8.1

17) Alone of all the Galilean moons, Callisto shows no sign of plate tectonics.

Diff: 2

Section Ref.:  8.1

18) It appears that while they are similar in size, Ganymede is much more differentiated than Callisto.

Diff: 2

Section Ref.:  8.1

19) In terms of composition and density, the atmosphere of Titan is closer to our own than any other place we have found in the solar system.

Diff: 1

Section Ref.:  8.2

20) Triton and Pluto both probably originated in the Kuiper Belt.

Diff: 1

Section Ref.:  8.2

21) Because the probe came so close, Voyager 1 sent back high resolution photos of detail on the surface of Titan in 1980.

Diff: 2

Section Ref.:  8.2

22) Titan’s surface has been mapped using Earth based visual telescopes.

Diff: 2

Section Ref.:  8.2

23) Methane drives the weather of Titan, for there it can be liquid, solid, or gas.

Diff: 2

Section Ref.:  8.2

24) Like Titan, Triton has a nitrogen atmosphere.

Diff: 2

Section Ref.:  8.2

25) The tectonic surface features we see on Triton are similar to the grooves of Ganymede.

Diff: 2

Section Ref.:  8.2

26) Alone among all the large moons, Triton orbits Neptune retrograde, and also at a 20 degree inclination to Neptune’s equator.

Diff: 2

Section Ref.:  8.2

27) Spacecraft have imaged erupting volcanoes on Io and Triton.

Diff: 2

Section Ref.:  8.2

28) The retrograde orbit of Triton dooms it to spiral inward toward Neptune, perhaps someday to make a ring system.

Diff: 2

Section Ref.:  8.2

29) Cassini’s probe Huygens returned images of what may have been a shoreline on Saturn.

Diff: 2

Section Ref.:  8.3

30) The haphazard terrain of Miranda suggests it was broken up by impact after it had differentiated, then fell back together as a jumbled maze.

Diff: 2

Section Ref.:  8.3

31) The surface of Saturn’s moon Enceladus is the most reflective of any in the solar system, suggesting very fresh ice is exposed.

Diff: 2

Section Ref.:  8.3

32) The rings of Uranus were discovered when it passed in front of a star, and the dark rings occulted the star several times for brief intervals.

Diff: 1

Section Ref.:  8.4

33) Saturn’s rings appear to be brighter and younger than the dirty, dark rings around Uranus and Neptune.

Diff: 1

Section Ref.:  8.4

34) All four ring systems orbit the equators of Jovian planets outside their Roche limits.

Diff: 2

Section Ref.:  8.4

35) Saturn’s rings are thick, perhaps a few thousand kilometers.

Diff: 2

Section Ref.:  8.4

36) At its equinoxes, Saturn’s rings are most open and double the planet’s brightness.

Diff: 2

Section Ref.:  8.4

37) The F-ring is held in place around Saturn by two shepherd moons.

Diff: 2

Section Ref.:  8.4

38) A resonance with Mimas clears out the ring particles from Cassini’s Division.

Diff: 2

Section Ref.:  8.4

39) Two sets of rings around Jovian planets were found by Earth-based observers, while two others were first imaged by the Voyagers.

Diff: 2

Section Ref.:  8.4

40) Probably the next satellite to get turned into ring debris will be Neptune’s backward moon, Triton.

Diff: 2

Section Ref.:  8.4

41) Saturn’s rings are extremely old, possibly older than four billion years.

Diff: 2

Section Ref.:  8.4

42) The particles in Saturn’s E ring probably come from volcanic eruptions on Enceladus.

Diff: 3

Section Ref.:  8.4

43) Neptune has a single, broad ring that is extremely thin.

Diff: 3

Section Ref.:  8.4

44) Like Saturn’s more famous ring system, Jupiter’s ring is also made of ice, just older and dirtier than the bright fresh material at Saturn.

Diff: 3

Section Ref.:  8.4

45) Pluto is smaller than many moons in the solar system.

Diff: 1

Section Ref.:  8.5

46) The initial prediction by Percival Lowell of Pluto’s position was close to the place it was, in fact, found by Clyde Tombaugh in 1930.

Diff: 2

Section Ref.:  8.5

47) Both Pluto and Charon are tidally locked to always keep the same faces toward each other, rotating and revolving around their common center of mass every 14.2 hours.

Diff: 2

Section Ref.:  8.5

48) Pluto is probably one of the largest of the Kuiper Belt bodies beyond Neptune.

Diff: 2

Section Ref.:  8.5

49) Based on our current knowledge of the motions of Uranus and Neptune, it is obvious that Pluto’s discovery was a triumph of physics, on par with Adams and Leverrier’s work in finding Neptune.

Diff: 3

Section Ref.:  8.5

50) Pluto is visible to the naked eye on extremely dark nights.

Diff: 2

Section Ref.:  8.5

51) Pluto is no longer classified as a planet.

Diff: 1

Section Ref.:  8.5

52) Pluto has only a single moon, Charon.

Diff: 1

Section Ref.:  8.5

53) Which element is critical to the formation of the volcanic surface of Io?

1. A) iron
2. B) silicon
3. C) sulfur
4. D) phosphorus
5. E) carbon

Diff: 1

Section Ref.:  8.1

54) What is thought to be the cause of Io’s volcanoes?

1. A) Jupiter’s magnetosphere and its charged particles
2. B) energy emitted by Jupiter
3. C) gravitational tidal stresses from both Jupiter and Europa
4. D) solar radiation focused by Jupiter’s gravity
5. E) radioactive decay in Io’s interior

Diff: 1

Section Ref.:  8.1

55) Which of the Galilean moons is densest and most geologically active?

1. A) Io
2. B) Europa
3. C) Ganymede
4. D) Callisto
5. E) Titan

Diff: 1

Section Ref.:  8.1

56) Which are the four Galilean moons of Jupiter?

1. A) Europa, Titan, Ganymede, and Callisto
2. B) Io, Ganymede, Callisto, and Titan
3. C) Europa, Ganymede, Io, and Triton
4. D) Io, Europa, Ganymede, and Callisto
5. E) Io, Titan, Triton, and Charon

Diff: 2

Section Ref.:  8.1

57) The surface of Europa is most like the Earth’s

1. A) tundra.
2. B) deserts.
3. C) Arctic Ocean.
4. D) Himalayan peaks.
5. E) South Pole.

Diff: 2

Section Ref.:  8.1

58) The weak magnetic fields around Europa and Ganymede were found during flybys of

1. A) Voyager 1.
2. B) Pioneer 10.
3. C) Cassini.
4. D) Galileo.
5. E) Stardust.

Diff: 2

Section Ref.:  8.1

59) In size and density, both Io and Europa resemble

1. A) Mercury.
2. B) our Moon.
3. C) Mars.
4. D) Pluto.
5. E) Charon.

Diff: 2

Section Ref.:  8.1

60) The mare on Ganymede were formed by

1. A) basalt erupting onto the surface.
2. B) plate tectonics.
3. C) gravitational interactions with Callisto and Europa.
4. D) water erupting and spreading over the surface.
5. E) sulfur spewed from volcanoes.

Diff: 2

Section Ref.:  8.1

61) In terms of dark, smoother mare and cratered highlands, which Jovian moon most resembles the near side of our own?

1. A) Io
2. B) Europa
3. C) Ganymede
4. D) Triton
5. E) Titan

Diff: 2

Section Ref.:  8.1

62) Of the Jovian satellites, which shows the oldest, most cratered surface?

2. B) Callisto
3. C) Triton
4. D) Ganymede
5. E) Miranda

Diff: 2

Section Ref.:  8.1

63) The largest moon in the solar system, bigger but not as massive as Mercury, is

1. A) Europa.
2. B) Ganymede.
3. C) Callisto.
4. D) Titan.
5. E) Triton.

Diff: 2

Section Ref.:  8.1

64) A moon with a smooth, uncratered surface would imply

1. A) meteorites have never struck the moon.
2. B) a strong magnetic field surrounds the moon.
3. C) the surface is very young.
4. D) the moon lies within the planet’s Roche Limit.
5. E) the surface is completely liquid.

Diff: 3

Section Ref.:  8.1

65) Which of these moons has the densest atmosphere?

1. A) Io
2. B) Europa
3. C) Callisto
4. D) Titan
5. E) Triton

Diff: 1

Section Ref.:  8.2

66) Which of these moons are most interesting to exobiologists?

2. B) Europa and Titan
3. C) Titan and Triton
4. D) Europa and Miranda
5. E) Triton and Charon

Diff: 2

Section Ref.:  8.2

67) At Titan, the lakes are made mostly of liquid

1. A) water.
2. B) carbon dioxide.
3. C) ethane.
4. D) metallic hydrogen.
5. E) nitrogen.

Diff: 2

Section Ref.:  8.2

68) The Huygens probe of the ESA made a successful landing on

1. A) Mars.
2. B) Europa.
3. C) Saturn.
4. D) Titan.
5. E) Triton.

Diff: 2

Section Ref.:  8.2

69) The atmosphere of Titan is composed mostly of

1. A) oxygen.
2. B) methane.
3. C) carbon dioxide.
4. D) hydrogen.
5. E) nitrogen.

Diff: 2

Section Ref.:  8.2

70) The grooves and ridges on Ganymede are thought to

1. A) be due to crustal tectonics motion (plate tectonics)
2. B) have formed within the last thousand years.
3. C) have grown considerably larger since the Voyager spacecraft discovered them.
4. D) be part of an ongoing volcanic process.
5. E) be due to the moon’s rapid rotation.

Diff: 3

Section Ref.:  8.2

71) What is true of Titan’s atmosphere?

1. A) It is similar to Earth’s in composition and density.
2. B) It is primarily hydrogen.
3. C) It is oxygen rich.
4. D) It was discovered by the Voyager 1
5. E) It has produced a runaway greenhouse effect.

Diff: 3

Section Ref.:  8.2

72) The erupting geysers of nitrogen gas on Triton

1. A) can be viewed by the Hubble Space Telescope.
2. B) are caused by a not yet determined internal energy source.
3. C) produced the large liquid oceans.
4. D) are increasing the moon’s rotation rate.
5. E) produced the frozen nitrogen surface.

Diff: 3

Section Ref.:  8.2

73) Voyager 1 was unable to image Titan’s surface because

1. A) of “smog” in Titan’s atmosphere.
2. B) of Titan’s high reflectivity.
3. C) the moon was in shadow during the mission.
4. D) the cameras were damaged by Saturn’s magnetic field.
5. E) volcanic activity spewed sulfur clouds, obscuring the surface.

Diff: 3

Section Ref.:  8.2

74) The brightest and probably youngest surface of any moon of Saturn belongs to

1. A) Titan.
2. B) Tethys.
3. C) Mimas.
5. E) Iapetus.

Diff: 2

Section Ref.:  8.3

75) Which Jovian moon shows the most diverse terrain, suggesting a violent impact broke it into many pieces, some of which reformed it as a jumbled puzzle?

1. A) Io
2. B) Ganymede
4. D) Miranda
5. E) Triton

Diff: 2

Section Ref.:  8.3

76) What statistic below has changed the most in the last decade?

1. A) the masses of the Galilean moons
2. B) the compositions of moons of Uranus
3. C) the rotational period of the Jovian moons
4. D) the densities of the larger moons
5. E) the number of known Jovian moons

Diff: 2

Section Ref.:  8.3

77) Which moon of Saturn shows the largest impact crater, relative to its size?

1. A) Titan
2. B) Callisto
3. C) Mimas
4. D) Miranda

Diff: 2

Section Ref.:  8.3

78) For a moon the same density as its planet, the Roche limit lies at ________ times the radius of its planet.

1. A) 1.4
2. B) 2.5
3. C) 3.6
4. D) 5.2
5. E) 7

Diff: 2

Section Ref.:  8.4

79) Why are the rings of Saturn so bright?

1. A) They are made of frozen metallic hydrogen.
3. C) They are made of metallic iron, never rusted by exposure to oxygen.
4. D) Light reflected off of gigantic Titan reinforces the sunlight.
5. E) They are made of young, fresh water ice.

Diff: 2

Section Ref.:  8.4

80) Which statement about Jupiter’s rings is true?

1. A) They are larger than Saturn’s, but darker.
2. B) They lie inside Jupiter’s Roche Limit.
3. C) They are made, in part, of material ejected by Europa’s volcanoes.
4. D) They are dark because their ices are dirtier than Saturn’s.
5. E) They were discovered by Galileo at the same time he discovered the moons.

Diff: 2

Section Ref.:  8.4

81) When Saturn is at Equinox, its rings will

1. A) double the planet’s brightness.
2. B) lie in the plane of the ecliptic.
3. C) contract closer to the planet’s surface.
4. D) appear face-on to the earth.
5. E) lie perpendicular to the plane of the ecliptic.

Diff: 2

Section Ref.:  8.4

82) What best explains the darkness of the rings beyond Saturn’s?

1. A) The sunlight is much fainter out there.
2. B) old, sooty debris and radiation darkening
3. C) Water ice reflects light poorly at the low temperatures beyond Saturn.
4. D) Rocky debris doesn’t reflect as well as water ice.
5. E) They are pieces of captured comets.

Diff: 2

Section Ref.:  8.4

83) The Cassini Division is a gap in Saturn’s rings caused by

1. A) Saturn’s excess heat.
2. B) two shepherding moons.
3. C) Saturn’s magnetic field.
4. D) gravitational interaction with Mimas.
5. E) the icy ring particles melting.

Diff: 2

Section Ref.:  8.4

84) Inside the Roche Limit

1. A) large moons are torn apart.
2. B) is where large moons form.
3. C) ring systems cannot exist.
4. D) there is a gap in a planet’s magnetic field.
5. E) hydrogen can only exist in its liquid metallic form.

Diff: 2

Section Ref.:  8.4

85) If Saturn takes about 30 years to orbit the Sun, and its rings were seen edge-on in 1995, when did they next appear most open at solstice?

1. A) 1998
2. B) 2002
3. C) 2005
4. D) 2007
5. E) 2010

Diff: 3

Section Ref.:  8.4

86) If Uranus takes 84 years to orbit the Sun, and Voyager 2 found its rings wide open at solstice in 1989, when will or did they next appear edge on, as seen from Earth?

1. A) 1995
2. B) 2003
3. C) 2010
4. D) 2025
5. E) They can never appear edge on, due to Uranus’ 98 degree axial tilt.

Diff: 3

Section Ref.:  8.4

87) Which was not a Voyager discovery about the rings of Saturn?

1. A) They have dark spokes that defy gravity.
2. B) They are made of tens of thousands of narrow ringlets.
3. C) There are hundreds of smaller moons imbedded in them, creating the gaps.
4. D) The F ring particles are herded by two shepherd moons.
5. E) The E ring may have been made by volcanic eruptions from Enceladus.

Diff: 3

Section Ref.:  8.4

88) Which of the following rings of Saturn lies closest to the planet?

1. A) the A ring
2. B) the B ring
3. C) the C ring
4. D) the E ring
5. E) the F ring

Diff: 3

Section Ref.:  8.4

89) Which moon orbits a body only twice as big as it is?

1. A) Triton
2. B) our Moon
3. C) Charon
4. D) Miranda
5. E) Mimas

Diff: 2

Section Ref.:  8.5

90) Pluto’s density is most similar to

1. A) the terrestrial planets.
2. B) the jovian planets.
3. C) the moons of the jovian planets.
4. D) Mercury, but not Venus, Earth, or Mars.
5. E) Saturn, but not Jupiter, Uranus, or Neptune.

Diff: 2

Section Ref.:  8.5

91) Pluto was discovered in

1. A) ancient times.
2. B) 1789.
3. C) 1859.
4. D) 1930.
5. E) 1992.

Diff: 2

Section Ref.:  8.5

92) The two names most associated with the discovery of Pluto are

2. B) Herschel and Bode.
3. C) Kuiper and Whipple.
4. D) Lowell and Tombaugh.
5. E) Shoemaker and Levy.

Diff: 2

Section Ref.:  8.5

93) Charon’s orbit

1. A) lies exactly in Pluto’s orbital plane.
2. B) is highly inclined to Pluto’s orbital plane.
3. C) is perpendicular to Pluto’s equator.
5. E) has not been determined yet.

Diff: 3

Section Ref.:  8.5

94) Pluto is most similar to

1. A) Europa.
2. B) Miranda.
3. C) Triton.
4. D) our Moon.
5. E) Mercury.

Diff: 2

Section Ref.:  8.5

95) What is so unusual about Pluto’s orbit?

1. A) It lies exactly on the ecliptic.
2. B) It has the lowest eccentricity of any planet’s orbit.
3. C) It is more inclined to the ecliptic than any of the eight planets.
4. D) It has an unexpectedly short orbital period.
5. E) Its orbital period is exactly twice that of Neptune’s.

Diff: 2

Section Ref.:  8.5

96) Ganymede and Callisto have densities suggesting they are made of rocky cores and mantles of ________.

Diff: 1

Section Ref.:  8.1

97) In general, the less cratered a moon’s surface, the ________ it is.

Diff: 1

Section Ref.:  8.1

98) To explain its magnetic field, Europa must have an ocean of ________.

Diff: 2

Section Ref.:  8.1

99) As we go outward from Io to Ganymede, the density of the moons ________.

Diff: 2

Section Ref.:  8.1

100) The Galilean moon of most interest to exobiologists is ________.

Diff: 2

Section Ref.:  8.1

101) The element erupting from the volcanoes of Io is ________.

Diff: 2

Section Ref.:  8.1

102) Europa is covered with an ocean of ________.

Diff: 2

Section Ref.:  8.1

103) A moon whose surface is smooth, with no craters, is probably ________.

Diff: 2

Section Ref.:  8.1

104) Compared to the size of Mercury, Ganymede is ________.

Diff: 2

Section Ref.:  8.1

105) The tidal stresses that create Io’s volcanism come from Jupiter and ________.

Diff: 3

Section Ref.:  8.1

106) The atmosphere of Titan is chiefly ________.

Diff: 1

Section Ref.:  8.2

107) The atmospheres of both Titan and Triton are mainly ________.

Diff: 1

Section Ref.:  8.2

108) The orbit of Triton is ________, very different from all other major moons.

Diff: 1

Section Ref.:  8.2

109) The lakes of Titan consist of liquid ________.

Answer:  ethane, methane, or just hydrocarbons

Diff: 2

Section Ref.:  8.2

110) On Neptune’s moon ________, geysers of liquid nitrogen rise 10 km high.

Diff: 2

Section Ref.:  8.2

111) The only Jovian moon to orbit its planet retrograde and out of the equatorial plane is ________.

Diff: 2

Section Ref.:  8.2

112) The Saturnian moon of most interest to exobiologists is ________.

Diff: 2

Section Ref.:  8.2

113) The next moon likely to be broken up into a ring is ________.

Diff: 3

Section Ref.:  8.2

114) The cantaloupe skin terrain of Triton is thought to be due to ________.

Answer:  faulting and deformation, or tectonic activity.

Diff: 3

Section Ref.:  8.2

115) One hemisphere of Enceladus may have the youngest surface of any of the jovian moons, with volcanoes spewing “ash” and “lava flows” of ________.

Diff: 2

Section Ref.:  8.3

116) The moon ________ may have erupted to create the E rings around Saturn.

Diff: 3

Section Ref.:  8.3

117) All four ring systems lie around their planet’s ________.

Diff: 1

Section Ref.:  8.4

118) All four rings systems lie within their planet’s ________.

Diff: 2

Section Ref.:  8.4

119) The striking gap between Saturn’s A and B rings is called the ________.

Diff: 2

Section Ref.:  8.4

120) The planet with the least obvious ring system is ________.

Diff: 2

Section Ref.:  8.4

121) The dusty ring around Jupiter was discovered in 1979 by ________.

Diff: 2

Section Ref.:  8.4

122) The F Ring around Saturn is maintained by ________.

Diff: 3

Section Ref.:  8.4

123) Pluto was named after the Roman god of the dark underworld, and also for ________.

Diff: 2

Section Ref.:  8.5

124) Pluto was discovered in 1930 by ________.

Diff: 2

Section Ref.:  8.5

125) It is likely that both Pluto and Triton were originally ________.

Answer:  Kuiper Belt Objects or KBOs

Diff: 2

Section Ref.:  8.5

126) It takes the Pluto-Charon system ________ to rotate around its common center of mass.

Diff: 3

Section Ref.:  8.5

127) Discovered in the 1990s, the ________ is a vaster, darker version of the more famed asteroid belt between Mars and Jupiter.

Diff: 1

Section Ref.:  8.5

128) Most astronomers now regard Pluto as the largest ________, and not a planet.

Answer:  Kuiper Belt Object, or KBO

Diff: 2

Section Ref.:  8.5

129) How are the large amounts of heating at Io generated?

Answer:  Io’s elliptical orbit causes variations in the gravitation pull of Jupiter and Europe. The changing force of gravity causes tidal stressing on Io’s interior by Jupiter and Europa, heating the moon.

Diff: 2

Section Ref.:  8.1

130) Contrast the volcanism of Io and Triton.

Answer:  Both are driven by tidal flexing, but at Io, it is sulfur erupting, while Triton is much colder, with liquid nitrogen geysers.

Diff: 2

Section Ref.:  8.2

131) In what two ways is the orbit of Triton unusual?

Answer:  It is 20 degrees off the equator of Neptune, and revolves clockwise or in retrograde motion, the only big moon to behave this way.

Diff: 3

Section Ref.:  8.2

132) What is the smallest of the Galilean moons? Why is it then the brightest?

Answer:  Europa has a very young, bright ice crust that reflects light well.

Diff: 3

Section Ref.:  8.2

133) What is the likely origin of Triton? Why do we believe this?

Answer:  It is probably a captured KBO. It orbits Neptune backwards (or retrograde), and well off from the planet’s equator.

Diff: 3

Section Ref.:  8.2

134) What is the future of Triton?

Answer:  In retrograde orbit, it will spiral inside Neptune’s Roche Limit, to be broken up into a new, spectacular ring around the blue world.

Diff: 3

Section Ref.:  8.2

135) Describe the Cassini mission to Saturn in 2004-5.

Answer:  The orbiter went into orbit about Saturn, to keep track of the weather on Saturn and survey the moons with higher resolution than the Voyagers could. It did the same kind of survey that Galileo did at Jupiter. But the Huygens lander touched down on the moon Titan, instead of going to Saturn itself.

Diff: 3

Section Ref.:  8.2

136) In what way could the Huygens probe be considered a first?

Answer:  It made the first successful soft landing on a moon other than Earth’s.

Diff: 3

Section Ref.:  8.2

137) The lakes on Titan have not been observed to have any waves. What does this suggest?

Answer:  This suggests the presence of viscous, tar-like hydrocarbons.

Diff: 3

Section Ref.:  8.2

138) Which moon of Saturn has the surface with the widest range of ages? Why?

Answer:  Enceladus has one ancient hemisphere, very cratered, but the other has been reworked with tectonic ridges and possibly volcanism as well. As with the mare on our own Moon, tidal forces act differentially on the two hemispheres.

Diff: 2

Section Ref.:  8.3

139) What makes the surface of Mimas so striking?

Answer:  The huge crater Herschel is a third as large as the moon.

Diff: 3

Section Ref.:  8.3

140) Which four moons are believed to have large bodies of liquid water?

Diff: 3

Section Ref.:  8.2, 8.3

141) How were the rings of Uranus discovered?

Answer:  In 1977, they passed in front of a star, and the star blinked off as its light was occulted by the dark rings.

Diff: 2

Section Ref.:  8.4

142) What do all four ring systems have in common?

Answer:  They are made of small debris orbiting in the equatorial place of Jovian planets, and within their Roche Limit.

Diff: 2

Section Ref.:  8.4

143) What is the relationship between Mimas and Saturn’s rings?

Answer:  The tidal resonance of Mimas causes ice to be cleared out from the Cassini Division.

Diff: 2

Section Ref.:  8.4

144) Define shepherd moons and give an example of them at work.

Answer:  The two small moons on each side of Saturn’s F ring herd the particles into this narrow, twisted ring.

Diff: 2

Section Ref.:  8.4

145) Define the Roche Limit.

Answer:  It is a region where the tidal stresses of a planet’s gravity would break apart any major moon that tried to orbit that close; it lies about 2.5 planetary radii out.

Diff: 2

Section Ref.:  8.4

146) The volcanic activity of Enceladus has what effect outside the moon itself?

Answer:  It is believed to have created the E ring of Saturn, which shares the same orbit as this moon.

Diff: 3

Section Ref.:  8.4

147) What would happen to a large moon inside the Roche Limit?

Answer:  Tidal forces would pull and tug the moon out of shape until it was torn apart. The pieces would eventually form a ring around the planet.

Diff: 3

Section Ref.:  8.4

148) Describe the odd rotations of Pluto and Charon.

Answer:  They are tidally fixed to keep the same faces toward each other during their 6.4-day periods of rotation.

Diff: 2

Section Ref.:  8.5

149) What is the closest thing to a binary planet we find in the solar system? Why?

Answer:  Pluto’s moon Charon is half as big as Pluto, and both objects are tidally fixed to always face each other during their 6.4 day rotations.

Diff: 2

Section Ref.:  8.5

150) What role did Percival Lowell play that led to the discovery and naming of Pluto?

Answer:  He predicted the existence of “Planet X” and its position, and began the search for it at his observatory before his death. When Clyde Tombaugh found it while continuing the search at Lowell Observatory, Pluto was close to the position Lowell had expected, but this turned out to be just luck.

Diff: 3

Section Ref.:  8.5

151) Contrast the densities and compositions of the four Galilean moons.

Answer:  Closer to Jupiter and dried out by its tides and radiation, Io and Europa are about as dense as our own Moon and made chiefly of rock. But larger Ganymede and Callisto are less stressed, less dense, and have extensive mantles of water and ice above their rock cores.

Diff: 2

Section Ref.:  8.1

152) How does counting craters help us estimate the age of a moon’s surface?

Answer:  Surface bombardment was much heavier early in the solar system’s history. A surface with few craters implies many, or all, of the early craters were covered up by lava flows or other activity. The fewer the craters and the smoother the surface, the younger we assume it to be. The smoothest surfaces are the youngest.

Diff: 3

Section Ref.:  8.1, 8.3

153) Why does the surface of Triton appear so young?

Answer:  When this KBO was trapped into orbit around Neptune recently, the tidal stresses of the retrograde capture orbit heated the interior, leading to the tectonic cantaloupe skin terrain and the liquid nitrogen geysers that covered almost all the craters.

Diff: 2

Section Ref.:  8.2

154) Why did Saturn’s rings appear very different in 1995 and 2003?

Answer:  At equinox in 1995, the thin rings almost disappeared as seen from Earth. By solstice in 2003, the rings were tilted 27 degrees toward the Sun and more than doubled the planet’s brightness.

Diff: 2

Section Ref.:  8.4

155) Name three ways that Saturn’s ring system is unique.

Answer:  It contains a lot more debris than all the other systems, it is made of young, bright shiny ice, it shows spoke patterns driven by the magnetic fields, and at solstice it is so bright it doubles the brightness of the planet.

Diff: 2

Section Ref.:  8.4

156) Using Jupiter’s axial tilt, explain why its rings are harder to observe from Earth than even the dark rings of Uranus.

Answer:  Like Saturn, the rings of Uranus can appear at a variety of tilts. But Jupiter has only a 5 degree axial tilt, so its rings are seen almost edge-on all the time.

Diff: 3

Section Ref.:  8.4

157) How would most planetary scientists classify Pluto? Why was this not done when it was found in 1930, misleading generations of elementary school children?

Answer:  It is the largest of the Kuiper Belt Objects, certainly neither a Jovian nor a terrestrial planet. It is comparable to Neptune’s moon Triton, which is also a captured KBO as well. We did not know about the Kuiper Belt until its discovery in 1992. Other similar Kuiper Belt Objects are now known as Plutoids.

Diff: 2

Section Ref.:  8.5

158) Why were the mass and density of Pluto unknown until Charon was found?

Answer:  Pluto is so distant that its disk was not resolved well, and it had no discernable gravitational influence on Uranus and Neptune (Lowell’s prediction was just luck). But Charon’s orbit let us find the mass of both objects, and the series of eclipses allowed us to calculate the sizes of both bodies with great accuracy.

Diff: 3

Section Ref.:  8.5

159) How did discovering the KBOs demote Pluto’s planetary status?

Answer:  If Pluto were to be considered a major planet, then many Kuiper Belt Objects are almost as big as Pluto, also orbit the Sun, some of them have moons also, and most are in more circular orbits closer to the ecliptic, behaving more like planets than Pluto does. Should they not also have been counted as planets as well?

Diff: 2

Section Ref.:  8.5

160) Based on its orbit, give two reasons to revoke Pluto’s planetary status.

Answer:  It does not orbit in the ecliptic, but off by 17 degrees. It also has a more eccentric orbit than even Mercury or Mars, and cut inside of the orbit of Neptune between 1979 and 1999 at perihelion.

Diff: 1

Section Ref.:  8.5

Chapter 18   Life in the Universe: Are We Alone?

1) From the beginnings of life on Earth, it took less than a billion years for single-celled organisms to evolve to multicellular organisms.

Diff: 1

Section Ref.:  18.1

2) Living cells have already been recreated in our laboratories.

Diff: 1

Section Ref.:  18.1

3) Organic molecules can only be made by living things.

Diff: 1

Section Ref.:  18.1

4) The definition of “life” requires only that an entity be able to reproduce itself.

Diff: 1

Section Ref.:  18.1

5) The Miller-Urey experiment did produce amino acids and proteins.

Diff: 2

Section Ref.:  18.1

6) The Miller-Urey experiment sought to recreate conditions in Earth’s early atmosphere.

Diff: 2

Section Ref.:  18.1

7) Life emerged on Earth about a billion years after the solar system formed.

Diff: 2

Section Ref.:  18.1

8) The Miller-Urey experiment relied on special conditions found only on Earth.

Diff: 2

Section Ref.:  18.1

9) Comets were likely a major agent in bringing both water and organic molecules to the surface of the early Earth.

Diff: 2

Section Ref.:  18.1

10) The transition from single to multicellular life took over two billion years.

Diff: 2

Section Ref.:  18.1

11) Astronomical events, such as an asteroid impact or nearly supernova, have probably altered the course of evolution on Earth.

Diff: 2

Section Ref.:  18.1

12) Europa is one of the most promising of the bodies in the outer solar system for life in its salty seas.

Diff: 2

Section Ref.:  18.2

13) Of the terrestrial planets, Mars seems most promising to exobiologists.

Diff: 1

Section Ref.:  18.2

14) NASA has found definite proof for the past existence of life on Mars.

Diff: 1

Section Ref.:  18.2

15) A Martian meteorite has revealed carbonate rocks and microfossils.

Diff: 2

Section Ref.:  18.2

16) Interest in life on Mars has died since the latest surveys have found no signs of liquid water on its surface now.

Diff: 2

Section Ref.:  18.2

17) The Murchison meteorite, a carbonaceous chondrite, contained many of the amino acids needed by living things on Earth.

Diff: 2

Section Ref.:  18.2

18) We have found Titan’s surface to have perfect living conditions for Earthlike life.

Diff: 2

Section Ref.:  18.2

19) The one term of the Drake equation whose value remains completely unknown is the average lifetime of a technological civilization.

Diff: 1

Section Ref.:  18.3

20) Binary star systems are considered good candidates in SETI.

Diff: 1

Section Ref.:  18.3

21) Each factor in the Drake Equation has a well-known, established value.

Diff: 1

Section Ref.:  18.3

22) The Drake Equation seeks to estimate the number of technological civilizations in the galaxy.

Diff: 1

Section Ref.:  18.3

23) Earth-like planets have been observed outside our solar system orbiting in the habitable zone.

Diff: 2

Section Ref.:  18.3

24) Of the billions of possible combinations of atoms into organic molecules, only about 1500 actually occur.

Diff: 2

Section Ref.:  18.3

25) An F-type star would have a larger habitable zone that does our Sun.

Diff: 2

Section Ref.:  18.3

26) Most bright blue stars we see with the naked eye are good candidates for life, since they have much larger habitable zones than does the Sun.

Diff: 2

Section Ref.:  18.3

27) The Milky Way Galaxy is forming about ten stars per month.

Diff: 2

Section Ref.:  18.3

28) Around Sun-like stars, we have, to date, only found Jupiter-like planets.

Diff: 2

Section Ref.:  18.3

29) The radio signals from Earth are greater than those from the Sun.

Diff: 1

Section Ref.:  18.4

30) Due to the first strong commercial radio stations, our radio presence has now extended out to approximately 70 light years.

Diff: 1

Section Ref.:  18.4

31) The water hole lies between 18 and 21 cm in wavelength in the radio spectrum.

Diff: 2

Section Ref.:  18.4

32) Most radio telescope searches for signs of intelligent life are performed in the water hole.

Diff: 2

Section Ref.:  18.4

33) Earth behaves as an artificial pulsar, with the strongest pulses for alien observers when North America is either rising or setting.

Diff: 2

Section Ref.:  18.4

34) As yet, no human probe has left our solar system and approached another star.

Diff: 2

Section Ref.:  18.4

35) Thanks to the far-flung Voyager and Pioneers, knowledge of our presence has now spread out over 30 light years.

Diff: 2

Section Ref.:  18.4

36) The water hole is a radio region with very low background noise.

Diff: 2

Section Ref.:  18.4

37) The water hole is a region around Sun-like stars where liquid water can exist on the surfaces of terrestrial planets.

Diff: 2

Section Ref.:  18.4

38) The probes sent out of our solar system were carefully designed to hide any trace of their origin.

Diff: 2

Section Ref.:  18.4

39) The Allen Telescope Array is one of the many radio searches for extraterrestrial life.

Diff: 2

Section Ref.:  18.4

40) As an artificial radio source, the spinning Earth would have a period of about a day.

Diff: 3

Section Ref.:  18.4

41) Which of the following appears most favored by natural selection?

1. A) intelligence
2. B) opposable thumbs
3. C) bipedal locomotion
4. D) binocular vision
5. E) live birth

Diff: 1

Section Ref.:  18.1

42) What important molecules of life did Miller and Urey brew up?

1. A) RNA
2. B) fatty acids
3. C) lean acids
4. D) amino acids
5. E) antacids

Diff: 1

Section Ref.:  18.1

43) Organic molecules are

1. A) living cells.
2. B) carbon-based.
3. C) silicon-based.
4. D) found only on Earth.

Diff: 1

Section Ref.:  18.1

44) The simplest life forms appeared on Earth when it was how old?

1. A) five million years
2. B) one billion years
3. C) 2.5 billion years
4. D) 3.5 billion years
5. E) 4.5 billion years

Diff: 1

Section Ref.:  18.1

45) How long between the evolution of single versus multicellular organisms?

1. A) 4.5 billion years
2. B) 2.5 billion years
3. C) one billion years
4. D) 600 million years
5. E) 63 million years

Diff: 2

Section Ref.:  18.1

46) Which of the following appears least important in the evolution of life here?

1. A) the stable luminosity of the Sun for billions of years
2. B) the magnetic field of the Earth
3. C) the presence of water and carbon atoms
4. D) an Earth-like atmosphere
5. E) the correct distance from the Sun

Diff: 2

Section Ref.:  18.1

47) How long ago did multicellular life forms appear in the fossil record?

1. A) 4.5 billion years ago
2. B) 3.8 billion years ago
3. C) one billion years ago
4. D) 63 million years ago
5. E) 30 million years ago

Diff: 2

Section Ref.:  18.1

48) The Murchison meteorite contained

1. A) living cells.
2. B) DNA.
3. C) 12 amino acids.
4. D) bacteria.
5. E) RNA.

Diff: 2

Section Ref.:  18.2

49) Large molecules found in meteorites and interstellar clouds are evidence that

1. A) life is abundant in the galaxy.
2. B) life has definitely formed in other places than Earth.
3. C) chemical evolution has taken place elsewhere in the universe.
4. D) organic molecules are extremely rare.
5. E) life originated on Mars before Earth.

Diff: 2

Section Ref.:  18.2

50) Which jovian moon has gotten the most attention from exobiologists?

1. A) Io
2. B) Ariel
3. C) Triton
4. D) Miranda
5. E) Europa

Diff: 2

Section Ref.:  18.2

51) What encouragement for life on Mars came from the Global Surveyor?

1. A) spectral evidence for chlorophyll
2. B) Hellas has a lake of salt water in its bottom.
3. C) The ice of the south polar cap is water, not dry ice.
4. D) strong photographic evidence for flowing and standing water on Mars in the past
5. E) The face on Mars is an artificial construct.

Diff: 2

Section Ref.:  18.2

52) Which type of molecules, vital to our life, were found to have survived a fiery descent to Earth on meteorites?

1. A) amino acids
2. B) DNA
3. C) lipids
4. D) sugars
5. E) vitamins

Diff: 3

Section Ref.:  18.2

53) According to our definition, we have been a technological civilization for about

1. A) 1000 years.
2. B) 10,000 years.
3. C) 100 years.
4. D) 10 years.
5. E) 500 years.

Diff: 1

Section Ref.:  18.3

54) Assuming the conditions ripe for life and intelligence abound in the Galaxy, what factor limits the number of galactic civilizations currently in existence?

1. A) the lack of metals for technology
2. B) the number of supernova explosions
3. C) the expansion of the universe
4. D) the average survival time of the civilizations
5. E) the speed of technological development

Diff: 1

Section Ref.:  18.3

55) Why do we feel type O and B stars are poor candidates for extraterrestrial life?

1. A) They do not have a habitable zone.
2. B) They don’t produce enough yellow light.
3. C) Their lifetime is too short.
4. D) They don’t produce a planetary system.
5. E) Their habitable zone lies too close to the star.

Diff: 2

Section Ref.:  18.3

56) If we are optimistic in our assumptions about the development of life and intelligence, then the number of technological civilizations currently in the galaxy should equal the

1. A) average lifetime of a civilization.
2. B) number of stars forming per year.
3. C) average number of planets per star.
4. D) number of stars in the galaxy’s habitable zone.
5. E) average number of planets that produce life.

Diff: 2

Section Ref.:  18.3

57) What is meant by the “habitable zone”?

1. A) the zone in which water can be a liquid around the center of the Galaxy
2. B) the region around each star in which terrestrial planets could have liquid water on their surfaces
3. C) the zone in which terrestrial-sized planets could form around each star
4. D) the region in dense atmospheres like Jupiter’s in which water droplets could form
5. E) the regions near the poles of Mercury in which liquid water might exist

Diff: 2

Section Ref.:  18.3

58) The Drake Equation is attempting to find

1. A) the number of planets in the Milky Way Galaxy.
2. B) the number of planets with life on them in the whole universe.
3. C) the number of stars that might have planets orbiting them.
4. D) the number of technological civilizations in the Galaxy at a given moment.
5. E) the total number of terrestrial planets ever created.

Diff: 2

Section Ref.:  18.3

59) How does Drake define a technological civilization?

1. A) one that can get into space
2. B) one that can communicate over interstellar distances
3. C) one that has a written language
4. D) one that can construct metal tools
5. E) one that can have the intelligence not to destroy itself

Diff: 2

Section Ref.:  18.3

60) In Drake’s equation, which of the following is the closest estimate for the number of stars that are formed in the Milky Way Galaxy?

1. A) a star a day
2. B) a star a month
3. C) a star a year
4. D) a star a decade
5. E) a star a century

Diff: 2

Section Ref.:  18.3

61) Considering both longevity and luminosity, which of these stars would be the most likely candidate for seeking extraterrestrial intelligence?

1. A) Spica, a B3 main-sequence star
2. B) 61 Cygni, a K2 main-sequence star
3. C) Sirius B, a white dwarf
4. D) Antares, a M3 supergiant
5. E) Barnard’s star, a M5 dwarf

Diff: 3

Section Ref.:  18.3

62) Most SETI searches are done at

1. A) X-ray wavelengths.
2. B) infrared wavelengths.
3. C) visual wavelengths.
5. E) gamma wavelengths.

Diff: 1

Section Ref.:  18.4

63) An extraterrestrial observer would pick up the strongest radio signals when

1. A) the Earth was at perihelion.
2. B) North America was either rising or setting for the observer.
3. C) North America was directly in front of the observers.
4. D) at new or full moon.
5. E) Saturday Night Live is on.

Diff: 2

Section Ref.:  18.4

64) As a radio source, the period of “pulsar Earth” is

1. A) 30 minutes.
2. B) 23 hours, 56 minutes.
3. C) 24 hours.
4. D) 29.5 days.
5. E) 365.25 days.

Diff: 3

Section Ref.:  18.4

65) Which of these radio waves would fall in the “water hole”?

1. A) 15,000 cm in wavelength.
2. B) 6.563 × 10-5cm in wavelength.
3. C) 19 cm wavelength
4. D) 150 cm in wavelength.
5. E) 243 cm in wavelength

Diff: 3

Section Ref.:  18.4

66) In addition to asteroids, ________ impacts also provided the primitive Earth with water and organics.

Diff: 2

Section Ref.:  18.1

67) Our earliest atmosphere, formed by outgassing, was much poorer in ________ than now.

Diff: 2

Section Ref.:  18.1

68) In the Miller-Urey experiment, the electric discharge was meant to simulate ________.

Diff: 2

Section Ref.:  18.1

69) Conducted in 1953, the ________ experiments were designed to show what types of complex molecules might have formed in the Earth’s primitive environment.

Diff: 3

Section Ref.:  18.1

70) Single-celled life ruled the Earth from ________ to ________ billion years ago.

Diff: 3

Section Ref.:  18.1

71) Outside our Earth, the most likely places for life are the planet ________ and jovian moon ________.

Diff: 1

Section Ref.:  18.2

72) The Murchison meteorite in Australia was found to contain ________.

Diff: 2

Section Ref.:  18.2

73) The ________ equation was written to assess the probabilities of technological, intelligent life existing in the Galaxy.

Diff: 1

Section Ref.:  18.3

74) In addition to the proper chemistry, it is ________ that determines the feasibility of life on a given planet.

Diff: 1

Section Ref.:  18.3

75) In the habitable zone, surface water must be at least partially ________ in phase.

Diff: 2

Section Ref.:  18.3

76) Cultural evolution has primarily taken place over the last ________ years.

Diff: 2

Section Ref.:  18.3

77) Besides comets and meteorites, we also find organic molecules in the ________ clouds in deep space.

Diff: 2

Section Ref.:  18.3

78) Compared to a G-type star, an F-type will have a ________ habitable zone.

Diff: 2

Section Ref.:  18.3

79) In a galaxy like ours, the best place for life to form would be in the ________.

Diff: 2

Section Ref.:  18.3

80) On average, the Milky Way forms about ________ stars per year.

Diff: 2

Section Ref.:  18.3

81) As the average estimated lifetime of a technical civilization increases, then the distances between neighboring civilizations would ________.

Diff: 2

Section Ref.:  18.3

82) We believe binary stars to be the ________ likely to have an extraterrestrial civilization.

Diff: 2

Section Ref.:  18.3

83) The cheapest and probably most effective means of interstellar communication is ________.

Diff: 1

Section Ref.:  18.4

84) As one of the strongest sources of radio waves in the solar system, the ________ has an observed period of about a day.

Diff: 1

Section Ref.:  18.4

85) The range of wavelengths for the “water hole” is ________ cm.

Diff: 2

Section Ref.:  18.4

86) The water hole is important to SETI because it is a ________ part of the radio spectrum.

Diff: 2

Section Ref.:  18.4

87) If a star system 30 parsecs distant is found to be broadcasting intelligent radio signals, then their news is already approximately ________ years old.

Diff: 2

Section Ref.:  18.4

88) How did the Miller-Urey experiment attempt to recreate early conditions on Earth?

Answer:  They combined gasses thought to be present in Earth’s early atmosphere and passed an electrical discharge through it to simulate lightning.

Diff: 2

Section Ref.:  18.1

89) What is an organic molecule based on? Why are they important?

Answer:  Carbon atoms. They can form the basic building blocks of life as we know it, such as amino acids and nucleotide bases.

Diff: 2

Section Ref.:  18.1

90) Compare the Copernican principle with the assumptions of mediocrity.

Answer:  Both assume we are nothing special, not in the center of anything, and without anything remarkable happening here that could not occur elsewhere.

Diff: 3

Section Ref.:  18.1

91) Why does Europa’s surface promise life of some kind?

Answer:  Europa has an icy surface below which there may be liquid water.

Diff: 2

Section Ref.:  18.2

92) What evidence did probes to Mars find that makes it a prime candidate for life?

Answer:  Water ice at the poles, photographic evidence of past flowing and standing water, and the rover Opportunity found its landing site was once drenched with water.

Diff: 2

Section Ref.:  18.2

93) Which factor in the Drake equation is the most uncertain?

Diff: 2

Section Ref.:  18.3

94) What is the primary determinant of whether a planet resides in the “habitable zone” of a planetary system?

Answer:  The distance from its star and hence the temperature of the planet’s surface to allow for formation of liquid water for life to evolve in.

Diff: 2

Section Ref.:  18.3

95) Which classes of stars with large habitable zones probably don’t last long enough for life to evolve to use them?

Answer:  Classes O through A are all probably too short-lived for life to get technical.

Diff: 2

Section Ref.:  18.3

96) Which class of stars probably has too small a habitable zone for life to arise?

Answer:  Class M stars are too cool to generate a large habitable zone.

Diff: 2

Section Ref.:  18.3

97) Why is Earth a stronger radio emitter than the Sun?

Answer:  Since many commercial FM radio stations came on the air we have been emitting a large amount of radio signals into space.

Diff: 1

Section Ref.:  18.4

98) Why does SETI concentrate on the water hole?

Answer:  The interval between the H and hydroxyl molecules is a very quiet part of the radio spectrum.

Diff: 2

Section Ref.:  18.4

99) Why is life difficult to define?

Answer:  Life must be able to react, grow, reproduce, and evolve. However, these rules are not hard and fast; things that are not alive, such as stars, may satisfy several of these requirements. Viruses do most of these things but are not generally considered to be alive either.

Diff: 2

Section Ref.:  18.1

100) Discuss the nature of the Miller-Urey experiments. What are the results of these experiments?

Answer:  The Miller-Urey experiments involved passing an electrical charge (“lightning”) through a “primordial soup” of chemicals believed to be similar to those which existed on early Earth. The result was the same simple amino acids found today in all living things on Earth.

Diff: 2

Section Ref.:  18.1

101) What do we mean by “life as we know it”?

Answer:  Our life is based on chains of carbon atoms with DNA, RNA, and proteins formed out of amino acids and nucleotides. Life as we know it depends on liquid water as its medium. It’s possible other atoms may also be suitable for life to be based on, which would be radically different from ours.

Diff: 2

Section Ref.:  18.1

102) What is meant by the idea life on Earth had an “interstellar origin”?

Answer:  Organic molecules have been found in comets and some meteorites. The large amount of water on Earth implies it was impacted by many comets in the past. Thus, organic molecules would have been introduced onto the Earth. Also, interstellar molecular clouds contain many complex molecules, which may have rained down on Earth during its formation.

Diff: 2

Section Ref.:  18.1

103) Why might the Cassini-Huygens probe to Titan be considered disappointing to exobiologists?

Answer:  Titan has a nitrogen atmosphere shrouded with dense hydrocarbon rich clouds, with lakes of liquid hydrocarbons, not unlike the Miller-Urey experiment. So it was thought to be a prime candidate for life as we know it. However, the conditions Huygens found were too cold for this.

Diff: 2

Section Ref.:  18.2

104) What three classes of stars are most likely to house life like ours? Why?

Answer:  F, G, and K are all similar enough to our Sun to have long life spans on the main sequence, and also hot enough to have fairly wide “habitable zones.”

Diff: 2

Section Ref.:  18.3

105) Define “technological civilization” according to Drake.

Answer:  Drake defined a technological civilization as a species capable of developing the technology to communicate with other species throughout the Galaxy

Diff: 2

Section Ref.:  18.3

106) What happened to the dinosaurs? How does that enter into the Drake Equation?

Answer:  Much of the life on Earth died in the Chicxulub impact 63 million years ago. The progress of life to intelligence can be set back by such impacts.

Diff: 2

Section Ref.:  18.3

107) Name each of the factors in the Drake equation.

Answer:  Number of technical civilizations is equal to:

average rate of star formation in the Galaxy x

fraction of stars with planets x

average number of planets suitable for life x

fraction of planets on which life arises x

fraction of these where life rises to intelligence x

fraction of these where the intelligence develops technology x

average life span of these technical civilizations.

Diff: 2

Section Ref.:  18.3

108) Describe the reasoning leading to the idea that the number of technological civilizations in the galaxy is equal to the average lifetime of a technological civilization.

Answer:  We know the rate of star formation, about 10 stars per year. Based on observations, we make a reasonable guess that there is one inhabitable planet in every 10 star systems. The factors involving the chance of intelligent, technological life arising we assign the maximum possible value of 1. The only factor we have no reasonable guess for is the lifetime of a technological civilization. So one times this is the number of civilizations we can expect to find.

Diff: 3

Section Ref.:  18.3

109) Why are type O, A, and M stars considered poor candidates to find a technological civilization?

Answer:  Considering the time it took life on Earth to arise, type O and A stars have too short a lifetime to give life a chance to evolve into higher forms. Type M stars are so cool that they have a very small habitable zone, thus reducing the likelihood a planet would be in the right position.

Diff: 3

Section Ref.:  18.3

110) What is the “water hole”? Why is so promising to radio astronomers?

Answer:  The “water hole” is the region of the radio spectrum between 18 cm (natural wavelength of the hydroxyl, OH, molecule) and 21 cm (natural wavelength of atomic hydrogen, H). Hydroxyl and hydrogen combine to form water, and the 18- to 21-cm region of the spectrum is relatively free of background noise. Thus it is believed that the so-called “water hole” is a natural band for communication between galactic civilizations.

Diff: 2

Section Ref.:  18.4

111) How would the radio Earth appear to extraterrestrials?

Answer:  Earth would be a stronger source of FM and TV waves than even our Sun. The peak signals would happen when eastern North America was rising or setting for the observer, and the entire pattern would repeat as the Earth rotated.

Diff: 2

Section Ref.:  18.4

112) Contrast space flight and radio communication as possible means of SETI.

Answer:  With current technology, space flight to the closest stars would still take thousands of years. Radio waves travel at the speed of light, and we have been broadcasting our location with commercial radio stations since the late 1930s. Everyone interested in such contact within 70 light years has been able to receive our signals by now.

Diff: 2

Section Ref.:  18.4

113) What is SETI? How is it being done?

Answer:  The Search for ExtraTerrestrial Intelligence is a systematic project listening to radio waves worldwide, by many teams and individuals, in the hope of detecting the first proof that an intelligent civilization beyond our solar system is broadcasting signals, either to contact us, or from random broadcasts, much as we are now sending our radio signals all over the Galaxy.

Diff: 2

Section Ref.:  18.4

114) What role did Frank Drake play in SETI?

Answer:  Frank Drake developed the equation that attempts to provide the number of technological, intelligent civilizations now present in the Galaxy by breaking it up into 7 different factors that might be individually analyzed.

Diff: 3

Section Ref.:  18.4

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