Astronomy Test 3

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Which of the following statements about our Sun is NOT true?

The Sun’s diameter is about five times that of Earth.
The Sun contains more than 99 percent of all the mass in our solar system.
The Sun is made mostly of hydrogen and helium.
The Sun is a star.

The Sun’s diameter is about five times that of Earth.

The planet in our solar system with the highest average surface temperature is __________.

Earth
Mercury
Venus
Neptune

Venus

Which jovian planet does NOT have rings?

Jupiter
Neptune
All the jovian planets have rings.
Uranus

All the jovian planets have rings.

What is the Kuiper belt?

a region of the solar system that extends almost a fourth of the way to the nearest stars and contains a trillion comets with orbits going in all directions around the Sun
the most prominent ring of Saturn that is visible in photographs
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets
a technical name for the asteroid belt

a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets

Which of the following statements about Pluto is true?

It is the largest known object that is considered to be a dwarf planet.
Its mass is a little less than Earth’s mass.
It is orbited by only one moon.
It has more in common with comets in the Kuiper belt than it does with terrestrial planets like Earth.

It has more in common with comets in the Kuiper belt than it does with terrestrial planets like Earth.

Suppose you view the solar system from high above Earth’s North Pole. Which of the following statements about planetary orbits will be true?

The inner planets orbit the Sun counterclockwise while the outer planets orbit the Sun clockwise.
The inner planets orbit the Sun clockwise while the outer planets orbit the Sun counterclockwise.
All the planets except Uranus orbit the Sun counterclockwise; Uranus orbits in the opposite direction.
All the planets orbit counterclockwise around the Sun.

All the planets orbit counterclockwise around the Sun.

When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals EXCEPT ______.

ammonia
carbon dioxide
water
methane

carbon dioxide

What is the Kuiper belt?

the most prominent ring of Saturn that is visible in photographs
a region of the solar system that extends almost a fourth of the way to the nearest stars and contains a trillion comets with orbits going in all directions around the Sun
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets
a technical name for the asteroid belt

a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets

What is the Oort cloud?

It is a giant storm in the atmosphere of Saturn.
It is another name for the cloud of gas from which our solar system was born.
It is a great cloud of gas that resides far beyond the orbit of Pluto.
It’s not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.

It’s not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.

In essence, the nebular theory holds that _________.

The nebular theory is a discarded idea that imagined planets forming as a result of a near-collision between our Sun and another star.
our solar system formed from the collapse of an interstellar cloud of gas and dust
the planets each formed from the collapse of its own separate nebula
nebulae are clouds of gas and dust in space

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

What do we mean by the frost line when we discuss the formation of planets in the solar nebula?

It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds.
It is the altitude in a planet’s atmosphere at which snow can form.
It is another way of stating the temperature at which water freezes into ice.
It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

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

According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?

It got hotter, its rate of rotation increased, and it flattened into a disk.
Its mass, temperature, and density all increased.

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

What is the giant impact hypothesis for the origin of the Moon?

The Moon formed just like Earth, from accretion in the solar nebula.
The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth.
The Moon formed when two gigantic asteroids collided with one another.
The Moon formed from material blasted out of Earth’s mantle and crust by the impact of a Mars-size object.

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

According to modern scientific dating techniques, approximately how old is the solar system?

10,000 years
4.5 billion years
14 billion years
4.6 million years

4.5 billion years

Which of the following types of material can condense into what we call ice at low temperatures?

hydrogen compounds
metal
hydrogen and helium
rock

hydrogen compounds

According to our theory of solar system formation, what are asteroids and comets?

leftover planetesimals that never accreted into planets
chunks of rock or ice that condensed after the planets and moons finished forming
chunks of rock or ice that were expelled from planets by volcanoes
the shattered remains of collisions between planets

leftover planetesimals that never accreted into planets

Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?

You’ll have 0.75 kilogram of the radioactive substance remaining.
You’ll have 0.25 kilogram of the radioactive substance remaining.
All the material will have completely decayed.
You’ll have 0.5 kilogram of the radioactive substance remaining.

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

Our Moon is about the same size as moons of the other terrestrial planets.

True
False

False

On average, Venus is the hottest planet in the solar system – even hotter than Mercury.

True
False

True

What’s unusual about our Moon?

It’s the only moon that orbits a terrestrial planet.
It’s by far the largest moon in the solar system.
It’s surprisingly large relative to the planet it orbits.

It’s surprisingly large relative to the planet it orbits.

Based on your study of the Interactive Figure, which of the following is not one of the four major features of the solar system?

Planets fall into two major categories (terrestrial and jovian).
Swarms of asteroids and comets populate the solar system.
Large bodies in the solar system have orderly motions.
The solar system contains eight planets plus dwarf planets (including Ceres, Pluto, and Eris).
Several exceptions to the general trends stand out.

The solar system contains eight planets plus dwarf planets (including Ceres, Pluto, and Eris).

Study the features relating to the first characteristic (orderly motions); click on the inner or outer solar system to see the planets in motion, then scroll over the planets to see diagrams of their axis tilts. Which of the following correctly describe patterns of motion in the solar system?
Check all that apply.

Inner planets orbit the Sun in the opposite direction from the outer planets.
The outer planets are so large that they nearly collide with each other on each orbit.
Planets closer to the Sun move around their orbits at higher speed than planets farther from the Sun.
The inner planets all rotate in the same direction (west to east) as Earth.
All the planets (not counting Pluto) orbit the Sun in nearly the same plane.
All the planets (not counting Pluto) have nearly circular orbits.

Planets closer to the Sun move around their orbits at higher speed than planets farther from the Sun. All the planets (not counting Pluto) orbit the Sun in nearly the same plane. All the planets (not counting Pluto) have nearly circular orbits.

Now consider the second major characteristic (two types of planets). Which of the following statements are true?
Check all that apply.

Jovian planets are higher in average density than terrestrial planets.
Jovian planets are larger in mass than terrestrial planets.
Jovian planets orbit farther from the Sun than terrestrial planets.
Jovian planets are larger in size than terrestrial planets.
Jovian planets have more moons than terrestrial planets.

Jovian planets are larger in mass than terrestrial planets. Jovian planets orbit farther from the Sun than terrestrial planets. Jovian planets are larger in size than terrestrial planets. Jovian planets have more moons than terrestrial planets.

The solar system contains vast numbers of small bodies, which we call asteroids when they are rocky and comets when they are icy. These small bodies are concentrated in the region(s) of the solar system that we call __________.
Check all that apply.

the Doppler belt
the Oort cloud
the Kuiper belt
the solar corona
the asteroid belt
the comet belt

the Oort cloud the Kuiper belt the asteroid belt

All the following statements are true. Which of them are considered to be "exceptions" to the general trends described by the first three major characteristics of the solar system?
Check all that apply.

Jupiter’s largest moon, Ganymede, is even larger than Earth’s moon.
Venus rotates in a direction opposite to the rotation of the other terrestrial planets.
Uranus rotates with an axis tilt that lies nearly in the ecliptic plane.
Pluto is in the outer solar system but is ice-rich in composition.
Our Moon has a diameter more than 1/4 the diameter of Earth.

Venus rotates in a direction opposite to the rotation of the other terrestrial planets. Uranus rotates with an axis tilt that lies nearly in the ecliptic plane. Our Moon has a diameter more than 1/4 the diameter of Earth.

Consider only the observed patterns of motion in the solar system. Scientifically, which of the following possible conclusions is justified from the patterns of motion alone?

The planets were not born within the past million years, but instead they must have been born billions of years ago.
The planets were not each born in a separate, random event.
The planets were born from a giant cloud of gas that rotated in the same direction that the Milky Way Galaxy rotates.
The planets started out quite small and grew to their current sizes as they gradually accreted more material.

The planets were not each born in a separate, random event.

Now consider why the observed patterns of motion lead to the conclusion that the planets were not born in separate, random events. The reason for this conclusion is that, if the planets had been born in separate, random events, we would expect that __________.

there would be many different types of planets, rather than just two major types
none of the planets would have ended up with moons
planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane
planets would orbit at much higher speeds than they actually do

planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane

Today, scientists have a theory (the nebular theory) that explains all the major characteristics of the solar system. In science, we expect a theory like this not only to explain the observed characteristics of our solar system but also to __________.

make testable predictions about other solar systems
predict which planets have life
predict some major change that will eventually occur in our own solar system

make testable predictions about other solar systems

Listed following are characteristics that can identify a planet as either terrestrial or jovian. Match these to the appropriate category.

Terrestrial planets: -small size -solid, rocky surface -located within the inner solar system Jovian planets: -primarily composed of hydrogen, helium, and hydrogen compounds -numerous orbiting moons -extensive ring systems -low average density

The following images show six objects in our solar system. Rank the objects from left to right based on their average distance from the Sun, from farthest to closest. (Not to scale.)

Farthest to closest: Pluto, Saturn, Jupiter, Mars, Earth, Mercury

The following images show six objects in our solar system. Rank these objects from left to right based on their mass, from highest to lowest. (Not to scale.)

Highest to lowest mass: Sun, Jupiter, Earth, Mars, Mercury, Pluto

The images below show six objects in our solar system. Rank these objects by size (average equatorial radius), from largest to smallest. (Not to scale.)

Largest to smallest radius: Sun, Jupiter, Earth, Mars, Mercury, Pluto

The following images show five planets in our solar system. Rank these planets from left to right based on their average surface (or cloud-top) temperature, from highest to lowest. (Not to scale.)

Highest to lowest temperature: Mercury, Earth, Mars, Jupiter, Neptune

The following images show five planets in our solar system. Rank these planets from left to right based on the amount of time it takes them to orbit the Sun, from longest to shortest. (Not to scale.)

Longest to shortest time: Neptune, Jupiter, Mars, Earth, Mercury

The following images show four planets in our solar system. Rank these planets from left to right based on the number of moons that orbit them, from highest to lowest. (Not to scale.)

Highest to lowest number: Jupiter, Mars, Earth, Mercury

The mass of the Sun compared to the mass of all the planets combined is like the mass of an elephant compared to the mass of a cat.

True
False

True

The weather conditions on Mars today are much different than they were in the distant past.

True
False

True

Moons cannot have atmospheres, active volcanoes, or liquid water.

True
False

False

Saturn is the only planet in the solar system with rings.

True
False

False

Which terrestrial planets have had volcanic activity at some point in their histories?

only Earth
Earth and Mars
all of them

all of them

Large moons orbit their planets in the same direction the planet rotates:

most of the time.
half of the time.
rarely.

most of the time.

Pluto orbits the Sun in the opposite direction of all the other planets.

True
False

False

How many of the planets orbit the Sun in the same direction that Earth does?

a few
most
all

All

What fraction of the moons of the planets orbit in the same direction that their planets rotate?

some
most
all

Most

When the solar nebula was about 40000 AU in radius, how fast would the same material have orbited? (Remember that when the cloud was larger, motions were more random, so we can calculate only the average.) Use the law of conservation of angular momentum (see Section Conservation Laws in Astronomy).

v≈5km/s
v≈0.1m/s
v≈10km/s
v≈5m/s

v≈5m/s

Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, as shown in the animation, the nebular theory predicts that a cloud will rotate rapidly once it shrinks to a small size. What physical law explains why a cloud will rotate rapidly as it collapses?

the law of conservation of angular momentum
the universal law of gravitation
the law of conservation of energy
Newton’s third law of motion
Kepler’s second law

the law of conservation of angular momentum

The nebular theory also predicts that the cloud should heat up as it collapses. What physical law explains why it heats up?

the law of conservation of energy
the law of conservation of angular momentum
Newton’s third law of motion
the universal law of gravitation
Kepler’s second law

the law of conservation of energy

The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk?

Gravity pulls more strongly on material along the rotation axis than perpendicular to it, bringing this material downward into a disk.
As a star forms near the cloud center, its wind blows away material that is not aligned with its equator, thereby leaving an equatorial disk of material.
All collapsing objects tend to flatten into a disk, regardless of their rotation.
Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole.

Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole.

As you’ve seen, the nebular theory predicts that a cloud that gives birth to planets should have the shape of a spinning disk. Which observable property of our solar system supports this prediction?

The orbit of Earth’s Moon lies very close to the ecliptic plane.
The four largest planets all have disk-shaped ring systems around them.
There are two basic types of planets: terrestrial and jovian.
All the planets orbit the Sun in the same direction and in nearly the same plane.

All the planets orbit the Sun in the same direction and in nearly the same plane.

The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system?

After the planets formed, the Sun’s gravity pulled the dense terrestrial planets inward, leaving only jovian planets in the outer solar system.
Denser particles of rock and metal sank into the inner solar system, leaving only gases in the outer solar system.
Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets.
All the planets started out large, but the Sun’s heat evaporated so much material that the inner planets ended up much smaller.

Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets.

Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems?
Check all that apply.

Planetary systems should generally have all planets orbiting in nearly the same plane.
Other planetary systems should have the same two types of planets: terrestrial and jovian.
Planetary systems should be common.
Planetary systems will always have four terrestrial planets and four jovian planets.
Jovian planets always form farther from their star than terrestrial planets.
Some planetary systems will have terrestrial planets that orbit their star in a direction opposite to the orbital direction of the jovian planets.

Planetary systems should generally have all planets orbiting in nearly the same plane. Other planetary systems should have the same two types of planets: terrestrial and jovian. Planetary systems should be common. Jovian planets always form farther from their star than terrestrial planets.

Listed following are statements that, based on our current theory of solar system formation, apply either to the formation of terrestrial planets or of jovian planets, but not both. Match these to the appropriate category.

Terrestrial planets: -surfaces dramatically altered during the heavy bombardment -accreted from planetesimals of rock and metal Jovian planets: -accreted from icy planetesimals -formed in a region of the solar system with lower orbital speeds -ejected icy planetesimals that are now Oort cloud comets -formed in regions cold enough -large moons formed in surrounding disks of material

What is Jupiter’s main ingredient?

rock and metal
hydrogen compounds
hydrogen and helium

hydrogen and helium

Which lists the major steps of solar system formation in the correct order?

collapse, accretion, condensation
collapse, condensation, accretion
accretion, condensation, collapse

collapse, condensation, accretion

Leftover ice-rich planetesimals are called

comets.
asteroids.
meteorites

comets.

Why didn’t a terrestrial planet form at the location of the asteroid belt?

There was never enough material in that part of the solar nebula.
The solar wind cleared away nebular material there.
Jupiter’s gravity kept planetesimals from accreting.

Jupiter’s gravity kept planetesimals from accreting.

The materials that made up the solar nebula can be categorized into the four general types as follows. Rank these materials from left to right based on their abundance in the solar nebula, from highest to lowest.

Highest to lowest abundance: hydrogen and helium gas, hydrogen compounds, rock, metals

The materials that made up the solar nebula can be categorized into these four general types. Rank these materials from left to right based on the temperature at which each would condense into a solid, from highest to lowest. Note: For a substance that does not condense at all, rank it as very low temperature.

Highest to lowest temperature: metals, rock, hydrogen compounds, hydrogen and helium gas

As you’ve learned from Part B, hydrogen and helium gas never condense under conditions found in the solar nebula. The remaining three categories of material in the solar nebula are shown again here. Rank these materials from left to right based on the distance from the Sun at which they could condense into a solid in the solar nebula, from farthest to closest.

Farthest to closest: hydrogen compounds, rock, metals

What substances were found within the inner 0.3 AU of the solar system before planets began to form?

nothing at all
only rocks and metals
only hydrogen compounds
only hydrogen and helium gases
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form

rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form

What substances existed as solid flakes within the inner 0.3 AU of the solar system before planets began to form?

none
only rocks and metals
only hydrogen compounds
only hydrogen and helium gases

none

Where would you expect terrestrial planets to form in the solar nebula?

within the inner 0.3 AU
anywhere between 0.3 AU and the frost line
anywhere outside 0.3 AU
anywhere outside the frost line

anywhere between 0.3 AU and the frost line

The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________.

only rocks and metals
only ices
rocks, metals, and ices
rocks, metals, ices, and hydrogen and helium gases

rocks, metals, and ices

Provided following are stages that occurred during the formation of our solar system. Rank these stages from left to right based on when they occurred, from first to last.

First to last stage: large cloud of gas and dust, contraction of solar nebula, condensation of solid particles, accretion of planetesimals, clearing the solar nebula

Sort the following hypothetical discoveries into the appropriate bins as follows:
Consistent with theory: The statement describes a discovery that we could reasonably expect to find if the nebular theory is correct.
Not consistent with theory: The statement describes a discovery that would force us to modify or discard the nebular theory.

Consistent with theory: -Beyond its jovian planets, a star has two ice-rich objects as large as Mars. -A star is surrounded by a disk of gas but has no planets. -Of a star’s 5 terrestrial planets, 1 has a moon as large as Earth’s moon. -A star has 20 planets. Not consistent with theory: -All 6 of a star’s terrestrial planets have a moon as large as Earth’s moon. -A star’s 4 jovian planets formed in its inner solar system and its 4 terrestrial planets formed farther out. – A star’s 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets. -A star has 9 planets, but none orbit in close to the same plane.

Two hypothetical discoveries in Part A deal with moons that, like Earth’s moon, are relatively large compared to their planets. Which of the following best explains why finding 1 planet with such a moon is consistent with the nebular theory, while finding 6 planets with such moons is not consistent?

Unusually large moons form in giant impacts, which are relatively rare events.
The nebular theory holds that moons of any size should be rare, so finding 1 is not too surprising but finding 6 would be very surprising.
The nebular theory says that only planets at least as large as Earth can have large Moons, and 6 Earth-size planets would not be likely to form in one solar system.

Unusually large moons form in giant impacts, which are relatively rare events.

Consider the hypothetical discovery from Part A reading: "A star’s 5 terrestrial planets orbit in the opposite direction of its 3 jovian planets." This discovery would be inconsistent with the nebular theory because the theory holds that __________.

terrestrial planets should orbit in a different plane from the plane of the jovian planets
star systems should have equal numbers of terrestrial and jovian planets
all the planets formed in a rotating, disk-shaped nebula

all the planets formed in a rotating, disk-shaped nebula

Consider the hypothetical discovery from Part A reading: "Beyond its jovian planets, a star has two ice-rich objects as large as Mars." This discovery is consistent with the nebular theory, because this theory predicts that _________.

ice-rich objects the size of terrestrial planets should exist in all solar systems
terrestrial planets sometimes form beyond the jovian planets
this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula

this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula

What’s the leading theory for the origin of the Moon?

It formed along with Earth.
It formed from the material ejected from Earth in a giant impact.
It split out of a rapidly rotating Earth.

It formed from the material ejected from Earth in a giant impact.

About how old is the solar system?

4.5 million years
4.5 billion years
4.5 trillion years

4.5 billion years

In a rock from the lunar maria, you find that 68% of the original uranium-238 remains, while the other 32% has decayed into lead. Is this rock older or younger than the highlands rock?

older
younger

younger

Assuming that other planetary systems form in the same way as our solar system formed, where would you expect to find terrestrial planets?

Terrestrial planets will likely be located farther from the planetary system’s star than any jovian planets.
Terrestrial planets will likely be located nearer the planetary system’s star than any jovian planets.
There is no way to know where terrestrial planets are likely to be.

Terrestrial planets will likely be located nearer the planetary system’s star than any jovian planets.

Compared to terrestrial planets, jovian planets are __________.

more massive and higher in average density
more massive and lower in average density
less massive and lower in average density
less massive and higher in average density

more massive and lower in average density

Which planet is approximately halfway between Pluto’s orbit and the Sun?

Mars, the fourth planet from the Sun
Jupiter, the fifth planet from the Sun
Saturn, the sixth planet from the Sun
Uranus, the seventh planet from the Sun

Uranus, the seventh planet from the Sun

The dwarf planet Eris was discovered in 2005, orbiting the Sun at an average distance about twice that of Pluto. In which of the following ways do Pluto and Eris differ from the terrestrial and jovian planets in our solar system?
Check all that apply.

Both Pluto and Eris are smaller than any of the terrestrial planets.
Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or jovian planets.
Both Pluto and Eris are denser than any of the terrestrial planets.
Both Pluto and Eris are less massive than any of the terrestrial or jovian planets.
Both Pluto and Eris have more hydrogen gas than any of the jovian planets.

Both Pluto and Eris are smaller than any of the terrestrial planets. Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or jovian planets. Both Pluto and Eris are less massive than any of the terrestrial or jovian planets.

1. _______ is about 30 times as far from the Sun as our own planet.

Neptune

2. _______ is the planet with the highest average surface temperature.

Venus

3. The planet with the lowest average density is______.

Saturn

4. The planet that orbits closest to the Sun is _________.

Mercury

5. The only rocky planet to have more than one moon is _______.

Mars

6. _________ is the jovian planet that orbits closest to the Sun.

Jupiter

7. _________ has a rotational axis that is tilted so much it lies nearly in the plane of its orbit.

Uranus

8. Most of the surface of _______ is covered with liquid water.

Earth

Which of the following is not a major pattern of motion in the solar system?

Nearly all comets orbit the Sun in same direction and roughly the same plane.
All of the planets orbit the Sun in the same direction – counterclockwise as viewed from above Earth’s north pole.
Most of the solar system’s large moons orbit in their planet’s equatorial plane.
The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun.

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

Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?

Terrestrial planets orbit much closer to the Sun than jovian planets.
Terrestrial planets are higher in average density than jovian planets.
Terrestrial planets contain large quantities of ice and jovian planets do not.
Jovian planets have rings and terrestrial planets do not.

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

Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt while icy comets are found primarily in the Oort cloud." What’s wrong with this statement?

The Kuiper belt contains icy comets, not rocky asteroids.
Comets are not really icy.
The Oort cloud has nothing to do with comets.
Asteroids are not really made of rock.
The statement is accurate as written.

The Kuiper belt contains icy comets, not rocky asteroids.

Which of the following is not a real difference between asteroids and comets?

Most asteroids are located much nearer to the Sun than most comets.
Asteroids orbit the Sun while comets just float randomly around in the Oort cloud.
Asteroids are made mostly of rock and comets are made mostly of ice.
It is thought that comets are far more numerous than asteroids.

Asteroids orbit the Sun while comets just float randomly around in the Oort cloud.

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

The diameter of Earth’s Moon is about 1/4 that of Earth.
Saturn has no solid surface.
Jupiter has a very small axis tilt.
Venus does not have a moon.

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

Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is ______.

much larger
just slightly less
much smaller
about the same

much larger

How is Einstein’s famous equation, E=mc 2, important in understanding the Sun?

It explains why the Sun is so massive.
It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each second.
It explains why the Sun has a magnetic field strong enough influence the atmospheres of the planets.
It explains why the Sun’s surface temperature is about 6,000°C.

It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each second.

Venus has a higher average surface temperature than Mercury. Why?

Because it is closer to the Sun.
Because its slow rotation gives it more time to heat up in sunlight.
Because its surface is heated by an extreme greenhouse effect.
Because its surface is covered with hot lava from numerous active volcanoes.

Because its surface is heated by an extreme greenhouse effect.

In what way is Venus most similar to Earth?

Both planets have very similar atmospheres.
Both planets have warm days and cool nights.
Both planets are nearly the same size.
Both planets have similar surface geology.

Both planets are nearly the same size.

Which of the following statements about the object called Eris is not true?

It orbits the Sun in the same general direction as the planets.
It lies well beyond Pluto and Neptune.
It is thought to be the first example of a new class of object.
It is slightly larger in mass than Pluto.

It is thought to be the first example of a new class of object.

Mars has two moons that are most similar in character to:

small asteroids
particles in the rings of Saturn
Earth’s Moon
comets.

small asteroids

Imagine that an alien spaceship crashed onto Earth. Which statement would most likely be true?

The crash would create a noticeable crater.
All the evidence of the crash would be quickly whisked off by the U.S. military to Area 51 in Nevada.
The aliens’ home world is another planet in our own solar system.
It would crash in the ocean.

It would crash in the ocean

Which planet listed below has the most extreme seasons?

Uranus
Jupiter
Earth
Mars

Uranus

In what way is Pluto more like a comet than a planet?

It sometimes enters the inner solar system.
It is made mostly of rock and ice.
It has moons.
It has a long tail.

It is made mostly of rock and ice.

Why was it advantageous for the Voyager mission to consist of flybys rather than orbiters?

Each individual spacecraft was able to visit more than one planet.
It was easier for data to be radioed back to Earth with flybys than orbiters.
Spacecraft making flybys can return to Earth more quickly than orbiters.
Flyby spacecraft can get closer to a planet than an orbiting spacecraft.

Each individual spacecraft was able to visit more than one planet.

Why has NASA sent recent orbiters to Mars (such as Mars Reconnaissance Orbiter) on trajectories that required them to skim through Mars’s atmosphere before settling into their final orbits?

It allowed the spacecraft to collect samples of the atmospheric gas for return to Earth.
It allowed the orbiters to get higher resolution pictures of the surface as it came close when skimming through the atmosphere.
Each spacecraft also carried a lander, and the lander could only be dropped to the Martian surface when the spacecraft passed through the atmosphere.
It saves money because the spacecraft uses atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines.

It saves money because the spacecraft uses atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines.

This photograph was taken on the surface of another world in our solar system. What world is it?

Venus
the Moon
Triton
Mars

Mars

Which pair of photos below shows Earth correctly scaled in comparison to the Sun?

When Earth is the smallest

What planet is this, and how do you know?

Saturn, because it is the only planet with rings.
Saturn, because of its colors and bright, wide rings.
Jupiter, because it is the biggest planet and has the biggest rings.
Neptune, because it has the brightest rings of any planet.
Jupiter, because of its colors and bright, wide rings.

Saturn, because of its colors and bright, wide rings.

Which pair of photos below shows Earth correctly scaled in comparison to Jupiter?

When Earth is the smallest

In this photograph, the large and bright object in the sky is:

a comet
a meteor
the northern lights
an asteroid

a comet

This famous photograph taken by the Voyager spacecraft shows _________.

A close-up of the rings of Neptune.
Earth as viewed from the outskirts of the solar system.
The Sun as viewed from the next-nearest star.
The cloud of gas and dust in which our solar system was born.

Earth as viewed from the outskirts of the solar system.

In this perspective view of the solar system, the sizes of the planets are ___________ relative to the sizes of their orbits.

correctly scaled
exaggerated about a million times
exaggerated about ten times
exaggerated about 1,000 times

exaggerated about a million times

This photo shows ___________.

a dwarf planet
Pluto
an asteroid
Mercury

an asteroid

What do we see in this photo?

Pluto
Venus
Eris
Mars
Neptune

Neptune

What planet is shown in this photo?

Mercury
Venus
Ganymede
Mars

Mars

1. The first few hundred million years of the solar system 19s history were the time of the __________, during which Earth suffered many large impacts.

heavy bombardment

2. The era of planet formation ended when the remaining hydrogen and helium gas of the solar nebula was swept into interstellar space by the __________.

solar wind

3. Ice can form from a gas through the process of ___________.

condensation

4. Hydrogen compounds in the solar system can condense into ices only beyond the __________.

frost line

5. Our Moon was most likely formed by a collision between Earth and a Mars-sized ____________.

planetesimal

6. Mars was formed by the ________ of smaller objects.

accretion

7. Our solar system was created by the gravitational collapse of the _________.

solar nebula

8. ______________ allows us to determine the age of a solid rock.

radiometric dating

What does this photo show?

a galaxy much like our Milky Way Galaxy
an interstellar cloud that probably looks almost identical to the way the solar nebula looked about 4.5 billion years ago
an interstellar cloud that will ultimately give birth to thousands of star systems
stars viewed through the atmosphere of Venus

an interstellar cloud that will ultimately give birth to thousands of star systems

This photo shows a "debris disk" around a nearby star. What is the significance of this type of "debris disk"?

It shows that stars really can be surrounded by flattened disks of dust and gas.
It proves that planets form in disks of dust and gas that surround stars.
It shows that stars can be encircled by disks that are enormous in size, sometimes extending halfway to other nearby stars.
It shows that the disks that encircle stars are sometimes split into two pieces, with one on each side of the star.

It shows that stars really can be surrounded by flattened disks of dust and gas.

This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why cloud spins faster as it shrinks in size?

the law of conservation of angular momentum
Kepler’s third law
Newton’s second law of motion
the law of conservation of energy
the universal law of gravitation

the law of conservation of angular momentum

This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why the center of the cloud becomes so much hotter as the cloud shrinks in size?

the universal law of gravitation
the law of conservation of energy
Newton’s second law of motion
the law of conservation of angular momentum
Kepler’s third law

the law of conservation of energy

This diagram represents the solar nebula early in its history, and shows the location of the <i>frost line</i>. Suppose you discover an object that is made of metal, rock, and ice. In which region of the solar system did it form?

1
2
3
4

4

This photo shows a slice of a meteorite. What is its significance?

It shows that accretion really did make objects many kilometers in size during the early stages of the formation of our solar system.
The structure and composition of the meteorite show that material that condensed beyond the frost line really did differ from material that condensed within the frost line.
The surprisingly flat face of the meteorite indicates that the solar nebula must have been very hot in the region in which this meteorite formed.
The shiny metal flakes embedded in rock are just what we expect if condensation really occurred as the nebular theory predicts.

The shiny metal flakes embedded in rock are just what we expect if condensation really occurred as the nebular theory predicts.

What is being shown in the zoom-out box of this painting?

the formation of Saturn’s rings
the formation of a jovian planet
the formation of a terrestrial planet
the solar nebula

the formation of a jovian planet

This painting shows an object colliding with Earth. What is thought to have happened as a result of this collision?

It led to the extinction of the dinosaurs.
The impact changed Earth’s orbit from one on which life would have been unlikely to our current orbit in which life flourishes.
The impact released the heat that allowed Earth to undergo differentiation.
It blasted away debris that then accreted in Earth orbit to form the Moon.

It blasted away debris that then accreted in Earth orbit to form the Moon.

What can you conclude from studying this graph?

It takes 5 billion years to turn potassium-40 into argon-40.
Argon-40 has a half-life of 1.25 billion years.
Both potassium-40 and argon-40 have half-lives of 1.25 billion years.
Potassium-40 has a half-life of 1.25 billion years.

Potassium-40 has a half-life of 1.25 billion years.

You find a rock containing radioactive potassium-40 and its decay product argon-40. You assume that all the argon-40 was made from radioactive decay of potassium-40. The rock now has twice as much argon-40 as potassium-40; that is, 2/3 of the original potassium-40 has decayed into argon-40 while 1/3 remains in the rock. Based on this graph, about how old is the rock?

3 billion years
2.5 billion years
1 billion years
1.25 billion years
2 billion years

2 billion years

Which of the following best explains why we can rule out the idea that planets are usually formed by near-collisions between stars?

A near collision might have created planets, but it could not have created moons, asteroids, or comets.
Studies of the trajectories of nearby stars relative to the Sun show that the Sun is not in danger of a near-collision with any of them.
A near collision should have left a trail of gas extending out behind the Sun, and we see no evidence of such a trail.
Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars.

Stellar near-collisions are far too rare to explain all the planets now known to orbit nearby stars.

According to our modern science, which of the following best explains why the vast majority of the mass of our solar system consists of hydrogen and helium gas?

All the other elements escaped from the solar nebula before the Sun and planets formed.
Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young.
All the other elements were swept out of the solar system by the solar wind.
Hydrogen and helium are produced in stars by nuclear fusion.

Hydrogen and helium are the most common elements throughout the universe, because they were the only elements present when the universe was young.

According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?

The law of conservation of angular momentum
Newton’s third law
The law of conservation of energy
The two laws of thermal radiation

The law of conservation of energy

According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

Einstein’s law E=mc2
The law of conservation of angular momentum
The law of conservation of energy
The law of universal gravitation

The law of conservation of angular momentum

According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?

It was fairly flat to begin with, and retained this flat shape as it collapsed.
The force of gravity pulled the material downward into a flat disk.
The law of conservation of energy.
It flattened as a natural consequence of collisions between particles in the nebula.

It flattened as a natural consequence of collisions between particles in the nebula.

What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?

The atomic mass numbers of various materials.
The locations of various materials in the solar nebula.
The amounts of energy required to ionize various materials.
The temperatures at which various materials will condense from gaseous form to solid form.

The temperatures at which various materials will condense from gaseous form to solid form.

According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?

Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets.
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it.
Both types of planet begun with planetesimals growing through the process of accretion, but only the jovian planets were able to capture hydrogen and helium gas from the solar nebula.

The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.

Many meteorites appear to have formed very early in the solar system’s history. How do these meteorites support our theory about how the terrestrial planets formed?

The meteorites sizes are just what we’d expect if metal and rock condensed and accreted as our theory suggests.
Their appearance and composition matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.
Their overall composition is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium.
The meteorites appearance and composition is just what we’d expect if metal and rock condensed and accreted as our theory suggests.

The meteorites appearance and composition is just what we’d expect if metal and rock condensed and accreted as our theory suggests.

According to present understanding, which of the following statements about the solar wind is not true?

It consists of charged particles blown off the surface of the Sun.
It is even stronger today than it was when the Sun was young.
It swept vast amounts of gas from the solar nebula into interstellar space.
It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today.

It is even stronger today than it was when the Sun was young.

According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?

The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
The water was mixed in the other materials in the planetesimals that accreted at our distance from the Sun.
Earth formed in the relatively narrow region of the solar nebular in which liquid water was plentiful.
The water was formed by chemical reactions among the minerals in the Earth’s core.

The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.

What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits?

Astronomers have observed moons being captured.
Some moons have a composition that differs from the composition of the planets
Some moons are surprisingly large in size.
Some moons have orbits that are "backwards" (compared to their planet’s rotation) or highly inclined to their planet’s equator.

Some moons have orbits that are "backwards" (compared to their planet’s rotation) or highly inclined to their planet’s equator.

Which of the following is not a line of evidence supporting the hypothesis that our Moon formed as a result of a giant impact?

The Pacific Ocean appears to be a large crater – probably the one made by the giant impact.
Computer simulations show that the Moon could really have formed in this way.
The Moon’s average density suggests it is made of rock much more like that of the Earth’s outer layers than that of the Earth as a whole.
The Moon has a much smaller proportion of easily vaporized materials than Earth.

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

Why are terrestrial planets denser than jovian planets?

Gravity compresses terrestrial planets to a higher degree, making them denser.
Only dense materials could condense in the inner solar nebula.
Actually, the jovian planets are denser than the terrestrial planets.
The Sun’s gravity gathered dense materials into the inner solar system.

Only dense materials could condense in the inner solar nebula.

Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?

3.75 billion years
1.25 billion years
2.5 billion years
5.0 billion years

3.75 billion years

How do scientists determine the age of the solar system?

Radiometric dating of meteorites
Radiometric dating of Moon rocks.
Radiometric dating of the oldest Earth rocks.
Theoretical calculations tell us how long it has taken the planets to evolve to their present forms

Radiometric dating of meteorites

The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars?

All the asteroids that formed between Mercury and Mars later migrated to the asteroid belt between Mars and Jupiter.
There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.
It was too hot for asteroids to form in this part of the solar system.
Gravity was too weak to allow asteroids to form in this part of the solar system.

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

About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first-generation star systems?

Like the jovian planets in our solar system, the jovian planets in these first-generation systems were orbited by rings.
These first-generation star systems typically had several terrestrial planets in addition to jovian planets.
There were no comets or asteroids in these first-generation star systems.
Jovian planets in these first-generation star systems had clouds made of water and other hydrogen compounds.

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

What is an extrasolar planet?

a planet that orbits a star that is not our own Sun
a planet that is extra large compared to what we’d expect
a planet that is larger than the Sun
a planet that is considered an "extra," in that it was not needed for the formation of its solar system

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

The first confirmed detections of extrasolar planets occurred in ____________.

2011
the mid-17th century
the 1990s
the mid-20th century

the 1990s

Based on available data, what kind of objects in our solar system do most of the known extrasolar planets resemble?

Kuiper belt objects
jovian planets
terrestrial planets
none of the above: most extrasolar planets apparently belong to some new category of object

jovian planets

Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?

In addition to the categories of terrestrial and jovian, there must be an "in-between" category of planet that has the mass of a jovian planet but the composition of a terrestrial planet.
Jovian planets can migrate from the orbits in which they are born.
In some star systems, it is possible for jovian planets to form in the inner solar system and terrestrial planets to form in the outer solar system.
Some of the "exceptions to the rules" in our own solar system are likely to have been the result of giant impacts.

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

Which detection techniques can find the planet’s orbital distance (assuming we know the mass of the star)?

only the Doppler technique
only the transit technique
only the astrometric technique
all of these techniques

all of these techniques

Why do we say that the Doppler technique gives the planet’s "minimum mass"?

The size of the Doppler shift that we detect depends on whether the planet’s orbit is tilted.
Extrasolar planets are always increasing in mass.
Doppler measurements are very difficult, producing noisy data that often cause astronomers to underestimate a planet’s mass.
The size of the Doppler shift that we detect depends on knowing the star’s mass, which can be very uncertain.

The size of the Doppler shift that we detect depends on whether the planet’s orbit is tilted.

How do we use velocity curves (obtained from spectroscopy) to show that some extrasolar planets are close to their host stars?

The velocity curve of the host star shows periods much longer than a year.
The velocity curve of the host star shows periods much shorter than a year.
The velocity curve of the extrasolar planet shows periods much shorter than a year.
The velocity curve of the extrasolar planet shows periods much longer than a year.

The velocity curve of the host star shows periods much shorter than a year.

Which of the following orbital characteristics has NOT been observed among any known extrasolar planets?
Check all that apply.

orbital speeds that are so slow that we cannot explain them
orbits that are much more eccentric than the orbits of planets in our own solar system
orbits that take the planets much closer to their star than Mercury orbits the Sun
orbits that are not elliptical

orbital speeds that are so slow that we cannot explain them orbits that are not elliptical

What method has detected the most extrasolar planets so far?

the transit method
Hubble images
the Doppler technique

the Doppler technique

Which one of the following can the transit method tell us about a planet?

its mass
its size
the eccentricity of its orbit

its size

Which method could detect a planet in an orbit that is face-on to the Earth?

Doppler technique
transits
astrometric technique

astrometric technique

Most extrasolar planets discovered so far most resemble

terrestrial planets.
jovian planets.
large icy worlds.

jovian planets.

Most known extrasolar planets are more massive than Jupiter because

we do not expect smaller planets to exist.
current detection methods are more sensitive to larger planets.
the Doppler method usually overestimates planet masses.

current detection methods are more sensitive to larger planets.

The following four graphs show the velocities, toward and away from Earth, of four identical stars. Assume that all four stars have extrasolar planets orbiting them at the same distance, and that the velocities are inferred by measuring Doppler shifts in the spectra of the stars. Rank the graphs from left to right based on the amount of orbital Doppler shift observed in each star’s spectrum, from smallest to largest.

Smallest Doppler shift to Largest Doppler shift: small wavelengths- small velocities to big wavelengths- large velocities

The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Part A). Assume that all four stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the amount of time that it takes the extrasolar planet orbiting each star to complete one orbit, from shortest to longest. If you think that two (or more) of the graphs should be ranked as equal, drag one on top of the other(s) to show this equality.

Shortest to longest amount of time: All of the velocities are equal.

The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Parts A and B). Assume that all four identical stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the mass of the extrasolar planet that orbits the star, from smallest to largest.

Smallest to largest mass: small wavelengths- small velocities to big wavelengths- large velocities

Which of the following properties can be inferred from the star’s orbital period?

the planet’s orbital radius
the planet’s mass
both the planet’s orbital radius and its mass
neither the planet’s orbital radius nor its mass

the planet’s orbital radius

Is it possible to determine the planet’s mass from the star’s velocity curve?

yes, by measuring both the star’s orbital period and its change in velocity over the orbit
yes, by measuring only the change in the star’s orbital velocity over the orbit
no, because the star’s spectrum cannot tell us about the planet
yes, by measuring the star’s orbital period only

yes, by measuring both the star’s orbital period and its change in velocity over the orbit

Consider the planet that causes the stellar motion shown in Plot 2 (be sure you have clicked the "Plot 2" button in the lower window of the animation). What can be said about a different planet orbiting the same star with an orbital period of 500 days?

The planet must be less massive.
The planet must be more massive.
The planet must be farther from the star.
The planet must be closer to the star.

The planet must be closer to the star.

Based on what we know about our own solar system, the discovery of hot Jupiters came as a surprise to scientists because these planets are __________.

made of different materials than either the terrestrial or jovian planets in our solar system
so close to their stars
so small
so large

so close to their stars

Our modern theory of solar system formation—the nebular theory—successfully accounts for all the major features of our own solar system. However, when the first hot Jupiters were discovered, their existence seemed inconsistent with the nebular theory because this theory predicts that __________.

jovian planets can form only in the cold, outer regions of a solar system
any system with jovian planets should also have terrestrial planets
planetary systems should be extremely rare
jovian planets located close to their stars should have evaporated by now

jovian planets can form only in the cold, outer regions of a solar system

The discovery of hot Jupiters led scientists to reconsider the nebuar theory. Which of the following best explains why the nebular theory(as it stood before the discoveries of extrasolar planets) had not predicted the existence of hot Jupiters?

There are no hot Jupiters in our solar system.
The nebular theory was fundamentally flawed and was incorrect about how planets form.
Scientists had no evidence that other stars could have disks of gas in which planets could form around.
The nebular theory was designed to apply only to our solar system, so there was no reason to think it would apply to others.

There are no hot Jupiters in our solar system.

Today, the leading hypothesis for the existence of hot Jupiters is that they formed in their outer solar systems and then migrated inward. Why did this hypothesis gain favor over alternative ideas?

Computer models that simulate planetary formation show that interactions between young planets and other material in the surrounding disk can cause planetary migration.
Scientists did not find any reason to favor any of the alternate explanations, so by process of elimination they settled on the migration hypothesis.
Telescopic observations have revealed several star systems in which planets can be seen migrating rapidly inward.
The migration hypothesis requires the least modification to the nebular theory and therefore was preferred over any alternatives.

Computer models that simulate planetary formation show that interactions between young planets and other material in the surrounding disk can cause planetary migration.

Assume that the migration hypothesis is the correct explanation for the hot Jupiters. In that case, the revised nebular theory looks just like the old theory, except that it now allows for the possibility of migration. Which of the following statements are consistent with this revised theory?
Check all that apply.

Terrestrial planets always form in the warm, inner regions of their star system.
Our solar system must be unusual because the jovian planets did not migrate inward.
Hot Jupiters can orbit their star in a direction opposite that of other jovian planets in the same system.
Jovian planets always form in the cold, outer regions of their star system.
Jovian planets can migrate inward and disrupt the orbits of terrestrial planets.

Terrestrial planets always form in the warm, inner regions of their star system. Jovian planets always form in the cold, outer regions of their star system. Jovian planets can migrate inward and disrupt the orbits of terrestrial planets.

The following images show four identical Sun-like stars and their companion planets, all traveling in circular orbits. In each case, the mass of the planet is given in Jupiter masses and the orbital distance is given in Astronomical Units (AU). Rank each case based on the strength of the gravitational force exerted by the extrasolar planet on its central star, from weakest to strongest. If you think that two (or more) diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Not to scale)

Weakest to strongest: One Jupiter Mass 2AU, Four Jupiter Masses 2 AU/One Jupiter Mass 1 AU (both are equal), Two Jupiter Masses 1 AU.

The following figures show four identical Sun-like stars and their companion planets. Each planet’s orbital distance is given in Astronomical Units (AU); note that in this case, all four planets have the same mass. Rank the extrasolar planets based on the amount of time it takes each to complete one orbit, from shortest to longest. (Not to scale)

Shortest to longest time: 1 AU, 1.5 AU, 2 AU, 2.5 AU

The following images show the set of four stars and planets as in Part B. Imagine that an Earth-based observer could see the motion of each of the stars edge-on. Rank each star based on the amount of Doppler shift we’d see in its spectrum as it moves in response to the gravitational tug of its planet, from smallest to largest. (Not to scale)

Smallest to largest Doppler shift: 2.5 AU, 2 AU, 1.5 AU, 1 AU

How is the planet 51 Pegasi different from Jupiter?

much closer to its star
much longer year
much more massive

much closer to its star

Which detection method can be used on a backyard telescope with a CCD system?

Doppler technique
transits
astrometric technique

transits

Compare this density to the average densities of Saturn (0.7g/cm3) and Earth (5.5g/cm3). Is the planet terrestrial or jovian in nature?

jovian planet
terrestrial planet

jovian planet

Which of two masses, if either, is larger.

The planet with the longer period is the larger one.
The planet with the shorter period is the larger one.
Their masses are equal.

The planet with the longer period is the larger one.

Each item describes a characteristic that applies to one of the three planet-detection methods shown following. Match the items to the correct planet-finding method.

Doppler method: -used for most of the first 200 extrasolar planet detections -currently best-suited to find Jupiter-sized extrasolar planets orbiting close to their stars Transit method: -planet-detection strategy of NASA’s Kepler Mission -allows for the extrasolar planet’s radius to be determined -this method was first to identify Earth-sized extrasolar planets -Can potentially detect planets in only a few percent of all planetary systems -looks for very slight, periodic dimming of a star Astrometric method: -measures precise changes in a star’s position in the sky, in fractions of arcseconds

1. The __________ was used to find a Jupiter-sized planet through careful measurements of the changing position of a star.

astrometric technique

2. Discovering planets through the __________ requires obtaining and studying many spectra of the same star.

Doppler technique

3. The __________ is currently searching for planet transits around some 100,000 stars.

Kepler mission

4. The ___________ is used to find extrasolar planets by carefully monitoring changes in a star’s brightness with time.

transit technique

5. The ___________ is being designed to measure very small changes in stellar positions, which should allow it to discover many extrasolar planets.

GAIA Astrometry Mission

6. Proposed plans for the _____________ would someday provide us with the first actual images and spectra of terrestrial worlds orbiting other stars.

Terrestrial Planet Finder mission

Why do scientists say that evolution is a "theory"?

because it is supported by only a small amount of evidence
because it’s really just a guess about how life developed on Earth
because it explains a great deal about life and is supported by an enormous body of evidence
because they are not very confident that it really happened

because it explains a great deal about life and is supported by an enormous body of evidence

In the Drake equation (Number of Civilizations ≡ N HP × f life × f civ × f now), what do we mean by f now?

the fraction of all species ever to exist that we currently are aware of
the fraction of planets with civilizations at the present time (as opposed to only in the past or future)
the fraction of civilizations in the universe that currently are sending messages to us
the fraction of planets in the galaxy on which a civilization could theoretically develop right now

the fraction of planets with civilizations at the present time (as opposed to only in the past or future)

Why don’t we expect to find life on planets orbiting high-mass stars?

The lifetime of a high-mass star is too short.
Planets cannot have stable orbits around high-mass stars.
The stars are too hot to allow for life.
The high-mass stars emit too much ultraviolet radiation.

The lifetime of a high-mass star is too short.

We have sent several spacecraft on trajectories that will ultimately take them into interstellar space (Pioneer 10 and 11, Voyager 1 and 2, New Horizons). How long will it take these spacecraft to travel as far as the nearest stars?

a few hundred years
tens of thousands of years
a few decades
about a thousand years
never, because they will rust and fall apart

tens of thousands of years

The graph above shows how a star’s orbital speed varies with time due to the gravitational tug of an orbiting planet. These data were obtained by measuring __________.

the precise brightness of the star divided by the precise brightness of the planet
the precise wavelengths of spectral lines in the spectrum of the orbiting planet
the orbital period of the planet that is orbiting the star
the precise wavelengths of spectral lines in the spectrum of the star

the precise wavelengths of spectral lines in the spectrum of the star

The graph above shows how a star’s orbital speed varies with time due to the gravitational tug of an orbiting planet. Based on these data, the planet’s orbital period is about:

2 days
6 days
4 days
50 days

4 days

This diagram shows the orbital path of the Sun around the center of mass of our solar system as it would appear from a distance of 30 light-years for the period 1960-2025. If aliens had constructed this graph at their home star system, they could learn all of the following except:

the orbital distance of Saturn
the fact that large, icy objects orbit the Sun in the Kuiper belt
the fact that the Sun has more than two planets
the mass and orbital period of Jupiter

the fact that large, icy objects orbit the Sun in the Kuiper belt

The four graphs below show Doppler data for four different stars. Assume that all four stars have planetary systems oriented the same way toward Earth, so that the data can be compared fairly. Which graph reveals the existence of a planet with the greatest mass?

Graph 1
Graph 2
Graph 3
Graph 4

Graph 2

The four graphs below show Doppler data for four different stars. Assume that all four stars have planetary systems oriented the same way toward Earth, so that the data can be compared fairly. Which graph reveals the existence of a planet with the longest orbital period?

Graph 1
Graph 2
Graph 3
Graph 4

Graph 4

This diagram represents a star with an orbiting planet that, as seen from Earth, periodically transits across the face of the star and disappears behind the star. If you measure the brightness of this system, at which point would it be brightest?

1
2
3
4

1

Each dot on this graph represents an extrasolar planet; the green dots (labeled) represent planets of our own solar system. What can you conclude about the extrasolar planets shown on this graph?

Most of the planets orbit in star systems that have at least three planets.
Nearly all of these planets orbit closer to their star than Mercury orbits to the Sun.
Many of these planets have orbits that differ significantly from perfect circles.
The farther away a planet is from its star, the greater its eccentricity.

Many of these planets have orbits that differ significantly from perfect circles.

This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet with the greatest mass?

1
2
3
4

4

This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet with the greatest density?

1
2
3
4

2

This graph plots planetary mass on the horizontal axis and radius on the vertical axis. Notice the four locations marked by the bold numbers 1 through 4. Which location represents a planet has about the same composition as Earth but is larger in both size and mass?

1
2
3
4

3

From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?

It causes the Sun to move in a small ellipse in the sky, with the same ellipse repeated every night.
It makes the Sun appear dimmer when viewed with infrared light.
It makes the Sun periodically appear to get dimmer and brighter.
It causes the Sun to move in a small ellipse with an orbital period of about 12 years.

It causes the Sun to move in a small ellipse with an orbital period of about 12 years.

Why is it so difficult to take pictures of extrasolar planets?

Their light is overwhelmed by the light from their star.
Extrasolar planets give off light at different wavelengths than planets in our solar system.
Telescopes are too busy with other projects.
No telescope is powerful enough to detect the faint light from a distant planet.

Their light is overwhelmed by the light from their star.

Suppose you are using the Doppler technique to look for planets around another star. What must you do?

Carefully examine a single spectrum of an orbiting planet.
Carefully examine a single spectrum of the star.
Compare many spectra of an orbiting planet taken over a period of many months or years.
Compare many spectra of the star taken over a period of many months or years.
Compare the brightness of the star over a period of many months or years.

Compare many spectra of the star taken over a period of many months or years.

In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

a massive planet that is close to its star
a low-mass planet that is far from its star
a massive planet that is far from its star
a low-mass planet that is close to its star

a massive planet that is close to its star

Suppose a planet is discovered by the Doppler technique and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.

its precise mass
its orbital period
its density
its physical size (radius)
its rotation period

its rotation period

The transit method allows us in principle to find planets around __________.

only stars of about the same mass and size as our Sun
only stars located within about 100 light-years of Earth
all stars that have planets of any kind
only a small fraction of stars that have planets

only a small fraction of stars that have planets

You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?

The planet must be closer to the star than Earth is to the Sun.
You do not have enough information to say anything at all about the planet.
The planet must be farther from the star than Neptune is from the Sun.
The planet must have a mass about the same as the mass of Jupiter.

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

Which of the following will allow you to learn something about a transiting planet’s atmospheric composition?

Use the Doppler method to study the planet throughout a cycle from one transit to the next.
Calculate the planet’s size, and then use size to infer what its atmospheric composition must be.
Compare spectra obtained before and during an eclipse.
Look for slight variations in the time between transits.

Compare spectra obtained before and during an eclipse.

Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that ________.

small planets are more difficult to detect than larger planets
small planets probably orbit too far from their stars to have been detected yet
small planets are usually made of materials that cannot be detected
small planets are extremely rare

small planets are more difficult to detect than larger planets

Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?

Planets always tend to orbit their star in the same direction and approximately the same plane.
Planets are common, and many or most stars have them.
Other planetary systems will have far more numerous asteroids and comets than actual planets.
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

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

To date, we’ve found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?

Planets at such distances are probably very low in mass.
No known technique can detect planets at such large distances.
Planets at such distances are extremely rare.
We have not yet been searching for planets at such distances for a long enough time.

We have not yet been searching for planets at such distances for a long enough time.

Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?

These planets migrated inward after being born on orbits much farther from their stars.
These planets were able to form close to their stars because their solar nebulas were very cold in temperature.
Despite their large masses, these planets are made of rock and metal and therefore could form in their inner solar systems.
These planets were captured from other solar systems.

These planets migrated inward after being born on orbits much farther from their stars.

Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn’t our own solar system end up with any hot Jupiters?

Our solar nebula must have stuck around for an unusually long time after the formation of jovian planets.
Our solar nebula must have been blown into space shortly after the formation of the jovian planets.
Our jovian planets must have migrated outward from inside the orbit of Mercury.
The existence of Earth and the other terrestrial planets prevented the jovian planets from migrating inward.

Our solar nebula must have been blown into space shortly after the formation of the jovian planets.

When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?

In just a few years, through analysis of observations by the James Webb Space Telescope.
In just a few years, through analysis of observations by the GAIA mission.
Any day now, thanks to our largest ground-based telescopes.
In a decade or two, through space observatories now in the early planning stages.

In a decade or two, through space observatories now in the early planning stages.

Listed below are several geological and biological events in Earth’s history. Rank the events in the order in which they occurred, from first to last.

First to last to occur: giant impact forms moon, end of heavy bombardment, early life (based on fossil evidence), oxygen build-up in atmosphere, animals colonize land, earliest mammals, dinosaurs go extinct

Earth was born about 4.5 billion years ago. According to current estimates, approximately how long after Earth’s formation did the Moon form?
The Moon formed
a few years later.
a few tens of millions of years later.
a few hundred million years later.
more than a billion years later.
at the same time as Earth.

a few tens of millions of years later.

The oldest fossil evidence of life dates to about __________ ago.

100 million years
1 to 2 billion years
3.5 to 4 billion years
4.5 billion years

3.5 to 4 billion years

Dinosaurs went extinct, probably because of an impact, about __________ ago.

5 million years
65 million years
200 million years
1 billion years

65 million years

Listed below are the names, spectral types (in parentheses), and approximate masses of several nearby main-sequence stars. Rank the stars based on the distances to their habitable zones (from the central star), from shortest to longest.

Smallest to largest distance: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica

Consider again the same set of five stars. This time, rank the stars based on the size (width) of their habitable zones, from smallest to largest.

Smallest to largest: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica

Imagine that each of the five stars is orbited by a terrestrial planet at a distance of 1 AU (Earth’s distance from the Sun). Rank the stars based on the planet’s expected surface temperature (not including any greenhouse effect), from lowest to highest.

Lowest temperature to highest temperature: Barnard’s star, 61 Cygni A, Alpha Centauri A, Sirius, Spica

To understand the difference between worlds that are potentially habitable and those that probably are not.
Part A
The items below describe worlds or selected localities on worlds. Based on our current scientific understanding, match these items to the appropriate category below.

Likely to be habitable: -underground on Mars -moon with atmosphere orbiting jovian planet 1 AU from 1 MSun star -subsurface ocean on Europa Unlikely to be habitable: -surface of Mars -volcanos on Io -surface of terrestrial planet 10 AU from 0.5 MSun star

Which statement explains the observations that make it seem possible that Mars could have life underground?

We have detected subsurface wells of liquid water in equatorial regions of Mars.
We have found surface liquid water on Mars, so it should also have water underground.
Mars is located within the Sun’s habitable zone.
We have detected water ice on Mars, and Mars still has some volcanic heat.

We have detected water ice on Mars, and Mars still has some volcanic heat.

In Part A you found that the terrestrial planet 10 AU from a 0.5MSun star is unlikely to be habitable. Could this planet be habitable if it were in a different orbit around its star?

Yes, if it had an eccentric orbit that sometimes brought it within 0.01 AU of its star.
Yes, but it would have to be less than 0.5 AU from its star.
No, because its star is too small to have a habitable planet.
Yes, if it were 1 AU from its star.

Yes, but it would have to be less than 0.5 AU from its star.

As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________.
Select from the choices in the format first blank / second blank.

increases / increases
decreases / increases
decreases / decreases
increases / decreases

increases / increases

Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case?

Only Mercury would be in the Sun’s habitable zone.
Mercury and Venus would be in the Sun’s habitable zone, but Earth and Mars would not.
Mercury, Venus, and Earth would be in the Sun’s habitable zone, but Mars would not.
All the terrestrial planets would be in the Sun’s habitable zone.

Only Mercury would be in the Sun’s habitable zone.

Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?

The expected lifetime of a massive star is too short to allow for the evolution of complex life
The habitable zone of a massive star is too far from the star to allow for the evolution of complex life
The habitable zone of a massive star covers too wide a range of distances from the star to allow for the evolution of complex life

The expected lifetime of a massive star is too short to allow for the evolution of complex life

1. High-mass main-sequence stars have a more distant and wider ________ than low-mass stars.

habitable zone

2. Sky surveys looking for radio signals generated by technology are part of the ______________.

search for extraterrestrial intelligence

3. The _________ is designed as a way of estimating the number of intelligent civilizations in the Milky Way.

Drake equation

4. The notion that living organisms with advantages that give them greater reproductive success (in some local environment) will survive while others perish is an example of what Darwin called _________.

natural selection

5. One of the key premises for the _________ is that living organisms are able to produce far more offspring than their environment can support.

theory of evolution

6. The different time periods of the ______________ are defined by changes in fossils found from those time periods.

geological time scale

7. Incoming ultraviolet light from the Sun can cause a __________ in a living organism’s DNA that can affect its ability to survive and reproduce.

mutation

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