Question 1

The numerical value given by the Drake equation

Accepted Answer

A)  is exactly 10. 
B)  is generally agreed to be around 10, certainly between 8 and 12. 
C)  could be almost any value from zero up to 1 billion. 
D)  has a lower limit of 1 but could be much larger than 10. 
A)  is exactly 10. 
B)  is generally agreed to be around 10, certainly between 8 and 12. 
C)  could be almost any value from zero up to 1 billion. 
D)  has a lower limit of 1 but could be much larger than 10. D

Question 2

In which of these environments have long-chain carbon-based molecules NOT been found?

Accepted Answer

A)  meteorites 
B)  massive interstellar clouds of gas and dust 
C)  surface of Earth 
D)  surfaces of planets and moons such as Venus and Jupiter's moon Callisto 
A)  meteorites 
B)  massive interstellar clouds of gas and dust 
C)  surface of Earth 
D)  surfaces of planets and moons such as Venus and Jupiter's moon Callisto D

Question 3

An important advance in the search for life elsewhere in the solar system was

Accepted Answer

A)  the discovery of primitive life-forms on Mars. 
B)  the replication in laboratories of silicon-based substitutes for the most important carbon-based life molecules. 
C)  the discovery of liquid water on Europa, Ganymede, and various other places in the solar system. 
D)  the discovery in meteorites of the remains of microbes. 
A)  the discovery of primitive life-forms on Mars. 
B)  the replication in laboratories of silicon-based substitutes for the most important carbon-based life molecules. 
C)  the discovery of liquid water on Europa, Ganymede, and various other places in the solar system. 
D)  the discovery in meteorites of the remains of microbes. C

Question 4

According to the present understanding, on which of these objects in this planetary system is it LEAST likely that life exists or existed at an earlier time?

Accepted Answer

A)  Mars 
B)  Callisto, a moon of Jupiter 
C)  Europa, a moon of Jupiter 
D)  Io, a moon of Jupiter 
A)  Mars 
B)  Callisto, a moon of Jupiter 
C)  Europa, a moon of Jupiter 
D)  Io, a moon of Jupiter

Question 5

Today, the habitable zone around the Sun includes

Accepted Answer

A)  only Earth. 
B)  Earth and Mars. 
C)  Earth and Venus. 
D)  Earth, Mars, and Venus. 
A)  only Earth. 
B)  Earth and Mars. 
C)  Earth and Venus. 
D)  Earth, Mars, and Venus.

Question 6

Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because

Accepted Answer

A)  radio signals that follow a recognizable pattern have been detected from this moon. 
B)  there appears to be large amounts of dark organic material spread on its surface. 
C)  changes seen in the dark lines crossing the icy surface have a spectral signature of vegetation. 
D)  there is strong evidence for liquid water beneath the thick ice layer on its surface. 
A)  radio signals that follow a recognizable pattern have been detected from this moon. 
B)  there appears to be large amounts of dark organic material spread on its surface. 
C)  changes seen in the dark lines crossing the icy surface have a spectral signature of vegetation. 
D)  there is strong evidence for liquid water beneath the thick ice layer on its surface.

Question 7

Which of these is NOT a reason carbon is thought to be the element on which complex extraterrestrial life is based?

Accepted Answer

A)  Carbon forms chemical bonds that are both strong and flexible. 
B)  Every life-form on Earth is carbon-based, over an immense range of conditions. 
C)  Carbon releases a significant amount of energy when it combines with hydrogen. 
D)  Carbon provides a basis for forming long, complex chains of molecules. 
A)  Carbon forms chemical bonds that are both strong and flexible. 
B)  Every life-form on Earth is carbon-based, over an immense range of conditions. 
C)  Carbon releases a significant amount of energy when it combines with hydrogen. 
D)  Carbon provides a basis for forming long, complex chains of molecules.

Question 8

Pioneer 10 and 11 carried plaques intended to show any alien civilization that found them the location of the solar system in the Galaxy. The location was marked relative to various pulsars (as seen in Figure 20-10b in the text). Which one of these is the BEST reason to choose pulsars for this purpose?

Accepted Answer

A)  Pulsars can be detected a long way across the Galaxy and thus presumably would be known to the aliens. 
B)  Pulsars can be identified uniquely by the frequencies of the radiation they emit. 
C)  Pulsar pulse rates are constant, never changing. 
D)  Pulsars form a more-or-less uniform ring around the galactic center (like the globular cluster halo) and thus provide a good coordinate system. 
A)  Pulsars can be detected a long way across the Galaxy and thus presumably would be known to the aliens. 
B)  Pulsars can be identified uniquely by the frequencies of the radiation they emit. 
C)  Pulsar pulse rates are constant, never changing. 
D)  Pulsars form a more-or-less uniform ring around the galactic center (like the globular cluster halo) and thus provide a good coordinate system.

Question 9

Which of these accurately explains the likelihood of technologically advanced civilizations forming within 1 kpc of the galactic center?

Accepted Answer

A)  There are likely to be MORE such civilizations near the galactic center, because the density of stars is so high there. 
B)  There are likely to be FEWER such civilizations near the galactic center, because the density of stars is so high there. 
C)  There are likely to be MORE such civilizations near the galactic center, because the stars are older there. 
D)  There are likely to be FEWER such civilizations near the galactic center, because they would have fallen into the Galaxy's central black hole.. 
A)  There are likely to be MORE such civilizations near the galactic center, because the density of stars is so high there. 
B)  There are likely to be FEWER such civilizations near the galactic center, because the density of stars is so high there. 
C)  There are likely to be MORE such civilizations near the galactic center, because the stars are older there. 
D)  There are likely to be FEWER such civilizations near the galactic center, because they would have fallen into the Galaxy's central black hole..

Question 10

What does the acronym SETI stand for?

Accepted Answer

A)  search for evidence of terrestrial-planet inhabitants 
B)  search for extraterrestrial intelligence 
C)  search for extraterrestrial invaders 
D)  sourcebook of extrasensory transient incidents 
A)  search for evidence of terrestrial-planet inhabitants 
B)  search for extraterrestrial intelligence 
C)  search for extraterrestrial invaders 
D)  sourcebook of extrasensory transient incidents

Question 11

What strategies and electromagnetic frequencies are thought to be the MOST logical for long-range communication across the universe with other intelligent beings?

Accepted Answer

A)  explosion of nuclear devices at specific intervals and in specific patterns across Earth when closest to a nearby star 
B)  night-by-night photography of nearby stars at hydrogen Balmer wavelengths 
C)  continuous radio and microwave listening and transmitting at frequencies at which the natural radio sky noise background is low 
D)  X-ray surveys of space at appropriate times (e.g., when Earth is closest to nearby stars in its orbit), in view of the penetrability of space at these wavelengths 
A)  explosion of nuclear devices at specific intervals and in specific patterns across Earth when closest to a nearby star 
B)  night-by-night photography of nearby stars at hydrogen Balmer wavelengths 
C)  continuous radio and microwave listening and transmitting at frequencies at which the natural radio sky noise background is low 
D)  X-ray surveys of space at appropriate times (e.g., when Earth is closest to nearby stars in its orbit), in view of the penetrability of space at these wavelengths

Question 12

Why do astronomers NOT consider stars with masses more than about 1.5 solar masses in the Drake equation when estimating the number of possible stars in the Milky Way Galaxy around which planets could form that would support intelligent life similar to humans?

Accepted Answer

A)  More massive stars would produce massive planets on which life would not be possible. 
B)  More massive stars would never reach temperatures sufficient to maintain life-supporting conditions on the surfaces of its planets. 
C)  A more massive star would produce so much damaging UV radiation that it would sterilize its planets. 
D)  More massive stars would have evolved so rapidly that an advanced civilization would not have had time to evolve and develop. 
A)  More massive stars would produce massive planets on which life would not be possible. 
B)  More massive stars would never reach temperatures sufficient to maintain life-supporting conditions on the surfaces of its planets. 
C)  A more massive star would produce so much damaging UV radiation that it would sterilize its planets. 
D)  More massive stars would have evolved so rapidly that an advanced civilization would not have had time to evolve and develop.

Question 13

The Drake equation attempts to predict the

Accepted Answer

A)  number of inhabitable planets around stars in the Milky Way Galaxy. 
B)  number of intelligent civilizations that exist in the whole universe. 
C)  probability of primitive life existing elsewhere in the Milky Way Galaxy. 
D)  number of technically advanced civilizations in the Milky Way Galaxy. 
A)  number of inhabitable planets around stars in the Milky Way Galaxy. 
B)  number of intelligent civilizations that exist in the whole universe. 
C)  probability of primitive life existing elsewhere in the Milky Way Galaxy. 
D)  number of technically advanced civilizations in the Milky Way Galaxy.

Question 14

Probably the MOST difficult factor to estimate in the Drake equation is

Accepted Answer

A)  R*, the rate at which solar-type stars form in the Galaxy. 
B)  fp, the fraction of stars that have planets. 
C)  ne, the number of planets per solar system that are Earthlike (suitable for life). 
D)  L, the lifetime of a technologically advanced civilization. 
A)  R*, the rate at which solar-type stars form in the Galaxy. 
B)  fp, the fraction of stars that have planets. 
C)  ne, the number of planets per solar system that are Earthlike (suitable for life). 
D)  L, the lifetime of a technologically advanced civilization.

Question 15

In which type of meteorite has evidence been found for organic molecules, some of which are in contrast to MOST life molecules on Earth?

Accepted Answer

A)  iron meteorite 
B)  stony iron meteorite 
C)  stony meteorite 
D)  carbonaceous chondrite 
A)  iron meteorite 
B)  stony iron meteorite 
C)  stony meteorite 
D)  carbonaceous chondrite

Question 16

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 103 and 104 MHz. What is the principal source of the natural signals in this frequency band?

Accepted Answer

A)  emissions from the water molecule 
B)  emissions from oxygen molecules 
C)  cosmic microwave background radiation 
D)  radio emission from terrestrial sources 
A)  emissions from the water molecule 
B)  emissions from oxygen molecules 
C)  cosmic microwave background radiation 
D)  radio emission from terrestrial sources

Question 17

The galactic habitable zone is sometimes defined as a torus around the galactic center with an outer radius of 10 kpc and an inner radius of 4 kpc. The volume of such a torus is roughly 5600 (kly)3. Adopting the text's value of N = 100 technologically advanced civilizations in the Galaxy, then, on the average, each volume of 56 (kly)3 within the galactic habitable zone is occupied by one such civilization. Also adopting the value L = 500 years as the technological lifetime of such a civilization (the time over which they have been sending out radio signals at the speed of light), then through what volume of space would these signals have spread? What are the chances of two civilizations being within the same signal volume?

Accepted Answer

A)  The volume of signals is 0.01 (kly)3, so the chances of two civilizations being within the same signal volume are very small. 
B)  The volume of signals is 0.5 (kly)3, so the chances of two civilizations being within the same signal volume are very small. 
C)  The volume of signals is 50 (kly)3, so the chances of two civilizations being within the same signal volume are reasonably good. 
D)  The volume of signals is 500 (kly)3, so the chances of two civilizations being within the same signal volume are very great. 
A)  The volume of signals is 0.01 (kly)3, so the chances of two civilizations being within the same signal volume are very small. 
B)  The volume of signals is 0.5 (kly)3, so the chances of two civilizations being within the same signal volume are very small. 
C)  The volume of signals is 50 (kly)3, so the chances of two civilizations being within the same signal volume are reasonably good. 
D)  The volume of signals is 500 (kly)3, so the chances of two civilizations being within the same signal volume are very great.

Question 18

Which of these observations regarding the likelihood of life existing elsewhere in the universe has NOT yet been made?

Accepted Answer

A)  discovery of assemblies of organic molecules into cell-like, self-replicating structures in the soils of Mars and the atmosphere of Venus 
B)  discovery of long-chain carbon-based molecules in interstellar clouds by radio astronomers 
C)  manufacture of organic compounds in laboratory simulations of primordial planetary atmospheres 
D)  discovery of long-chain amino acid protein molecules in meteorites 
A)  discovery of assemblies of organic molecules into cell-like, self-replicating structures in the soils of Mars and the atmosphere of Venus 
B)  discovery of long-chain carbon-based molecules in interstellar clouds by radio astronomers 
C)  manufacture of organic compounds in laboratory simulations of primordial planetary atmospheres 
D)  discovery of long-chain amino acid protein molecules in meteorites

Question 19

Part of determining the Drake factor R* is determining what is a "Sunlike star," a star around which a habitable planet could orbit. What is the thinking concerning low-mass stars, that is, stars with masses less than about half a solar mass? (These are stars cooler than M0 type main-sequence stars.)

Accepted Answer

A)  Low-mass stars are highly desirable here because they tend to live longer and allow more time for life to develop and form a civilization. 
B)  Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But they are still acceptable as Sunlike stars. 
C)  Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But this means they will be tidally locked into synchronous rotation, with one very hot side and one very cold side- not an acceptable situation. 
D)  Photosynthesis, the main energy-production mechanism in green plants on Earth, works best with shorter wavelengths of light. These low-mass red stars tend to produce less of these shorter wavelengths and thus could not support efficient photosynthesis. 
A)  Low-mass stars are highly desirable here because they tend to live longer and allow more time for life to develop and form a civilization. 
B)  Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But they are still acceptable as Sunlike stars. 
C)  Planets would have to orbit relatively close to low-mass stars in order to be warm enough to be in the habitable zone. But this means they will be tidally locked into synchronous rotation, with one very hot side and one very cold side- not an acceptable situation. 
D)  Photosynthesis, the main energy-production mechanism in green plants on Earth, works best with shorter wavelengths of light. These low-mass red stars tend to produce less of these shorter wavelengths and thus could not support efficient photosynthesis.

Question 20

It is unlikely that intelligent life would develop on a planet circling a star of significantly less mass than the Sun because

Accepted Answer

A)  no moon would form around a planet near such a star, and the Moon is considered to have been essential for the evolution of life because of tidal variations on Earth. 
B)  the lifetime of such a star on the main sequence is too short; life-forms on such a planet would not have time to evolve intelligence. 
C)  the planet would probably become tidally locked to the star, making one side of the planet too hot and the other side too cold. 
D)  there would be no region around the star where UV, visible, and IR light intensities would be suitable for the evolution of life. 
A)  no moon would form around a planet near such a star, and the Moon is considered to have been essential for the evolution of life because of tidal variations on Earth. 
B)  the lifetime of such a star on the main sequence is too short; life-forms on such a planet would not have time to evolve intelligence. 
C)  the planet would probably become tidally locked to the star, making one side of the planet too hot and the other side too cold. 
D)  there would be no region around the star where UV, visible, and IR light intensities would be suitable for the evolution of life.

The numerical value given by the Drake equation

In which of these environments have long-chain carbon-based molecules NOT been found?

An important advance in the search for life elsewhere in the solar system was

According to the present understanding, on which of these objects in this planetary system is it LEAST likely that life exists or existed at an earlier time?

Today, the habitable zone around the Sun includes

Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because

Which of these is NOT a reason carbon is thought to be the element on which complex extraterrestrial life is based?

Which of these accurately explains the likelihood of technologically advanced civilizations forming within 1 kpc of the galactic center?

What does the acronym SETI stand for?

What strategies and electromagnetic frequencies are thought to be the MOST logical for long-range communication across the universe with other intelligent beings?

Why do astronomers NOT consider stars with masses more than about 1.5 solar masses in the Drake equation when estimating the number of possible stars in the Milky Way Galaxy around which planets could form that would support intelligent life similar to humans?

The Drake equation attempts to predict the

Probably the MOST difficult factor to estimate in the Drake equation is

In which type of meteorite has evidence been found for organic molecules, some of which are in contrast to MOST life molecules on Earth?

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 10³ and 10⁴ MHz. What is the principal source of the natural signals in this frequency band?

Which of these observations regarding the likelihood of life existing elsewhere in the universe has NOT yet been made?

It is unlikely that intelligent life would develop on a planet circling a star of significantly less mass than the Sun because

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Filters

Exam 20: Astrobiology

The numerical value given by the Drake equation

In which of these environments have long-chain carbon-based molecules NOT been found?

An important advance in the search for life elsewhere in the solar system was

According to the present understanding, on which of these objects in this planetary system is it LEAST likely that life exists or existed at an earlier time?

Today, the habitable zone around the Sun includes

Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because

Which of these is NOT a reason carbon is thought to be the element on which complex extraterrestrial life is based?

Which of these accurately explains the likelihood of technologically advanced civilizations forming within 1 kpc of the galactic center?

What does the acronym SETI stand for?

What strategies and electromagnetic frequencies are thought to be the MOST logical for long-range communication across the universe with other intelligent beings?

Why do astronomers NOT consider stars with masses more than about 1.5 solar masses in the Drake equation when estimating the number of possible stars in the Milky Way Galaxy around which planets could form that would support intelligent life similar to humans?

The Drake equation attempts to predict the

Probably the MOST difficult factor to estimate in the Drake equation is

In which type of meteorite has evidence been found for organic molecules, some of which are in contrast to MOST life molecules on Earth?

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 103 and 104 MHz. What is the principal source of the natural signals in this frequency band?

Which of these observations regarding the likelihood of life existing elsewhere in the universe has NOT yet been made?

It is unlikely that intelligent life would develop on a planet circling a star of significantly less mass than the Sun because

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Filters

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 10³ and 10⁴ MHz. What is the principal source of the natural signals in this frequency band?