Question 1

How did the temperature of the solar nebula develop?
A)The nebula formed from cold gas and dust, and it remained cold until sufficient oxygen had accumulated so that combustion was possible.
B)The nebula formed from cold gas and dust, and it remained cold until nuclear reactions developed.
C)The gas and dust remained cold as they collapsed to form a much denser nebula. Here friction developed between the particles, and this gradually raised the temperature.
D)As the nebula collapsed, gravitational potential energy was converted into kinetic energy, and the temperature rose.

Accepted Answer

As the solar nebula collapsed, gravitational potential energy was converted to kinetic energy, leading to an increase in the temperature. This process continued until the temperature was sufficiently high for nuclear reactions to take place, leading to the formation of the Sun.

Question 2

Which of these statements is an example of Kelvin-Helmholtz contraction?
A)a contraction of the planet Mercury as it cooled, with consequent buckling of the surface
B)a contraction of a dense cloud of gas slowly gets hotter due to the release of gravitational energy
C)the condensation of ices (e.g., ammonia) onto dust particles in the early solar nebula
D)a contraction of a thin cloud of gas, in which the temperature remains constant due to the escape of infrared radiation

Accepted Answer

Kelvin-Helmholtz contraction occurs when a dense cloud of gas contracts and heats up due to the release of gravitational energy. This process is often seen in young stars and can also occur in certain atmospheric phenomena. Option A refers to thermal contraction, not Kelvin-Helmholtz contraction. Option C refers to the process of protoplanetary disk formation, not Kelvin-Helmholtz contraction. Option D refers to a scenario where the temperature remains constant, which is not consistent with Kelvin-Helmholtz contraction.

Question 3

The most likely mechanism for the solar system's formation appears to be:
A)a capture theory in which the planets were formed elsewhere and were captured by the gravitational pull of the Sun as they drifted through space.
B)the idea that the planets were formed deep in the interior of the Sun and were later flung out by the Sun's angular momentum.
C)that the solar system was once a galaxy, from which the Sun and planets are the remnants.
D)that a cloud of gas and dust condensed to form the Sun, while planets formed later by condensation and accretion within the nebular disk.

Accepted Answer

The most widely accepted theory for the solar system's formation is the nebular hypothesis, which suggests that a cloud of gas and dust (a nebula) collapsed due to gravity, which caused it to spin and eventually flatten into a disk shape. The central part of this disk became the Sun, while the surrounding material clumped together to form the planets through a process of accretion (collecting particles and growing larger). This theory is supported by observations of other star-forming regions and the composition of the planets and asteroids in our solar system.

Question 4

To be accepted as a reasonable picture of the formation of the solar system, the nebular hypothesis must explain all of the these statements except one. Which is the exception?
A)All the planets orbit the Sun in the same direction.
B)All the planetary orbits lie close to the ecliptic.
C)The magnetic fields vary greatly in magnitude and direction.
D)The vast bulk of the solar system's mass lies in the center.

Accepted Answer

The nebular hypothesis explains the formation of the solar system from a rotating cloud of gas and dust. However, it does not provide an explanation for the variation in magnetic fields in the solar system. Magnetic fields are generated by the motion of charged particles within a planet or star, not by the initial formation of the solar system. Therefore, statement C is not explained by the nebular hypothesis. Statements A, B, and D are all explained by the hypothesis – the planets formed from the same rotating cloud, hence they all orbit in the same direction and lie close to the ecliptic, and the vast bulk of the mass in the solar system lies in the central mass of the sun.

Question 5

In a rotating physical system (e.g., a star formation region or a skater), what happens to the rotation rate (or angular speed) when the mass of the system condenses toward the center of rotation?
A)It varies periodically.
B)It decreases.
C)Since rotation depends only on the initial rotation speed, it remains the same.
D)It increases.

Accepted Answer

In a rotating physical system, the moment of inertia decreases as the mass moves towards the center of rotation. This results in an increase in the rotation rate (angular speed) in order to conserve angular momentum. This phenomenon is also known as the conservation of angular momentum. Therefore, the correct answer is D - it increases.

Question 6

As the early Sun got smaller in a Kelvin-Helmholtz contraction, its interior became hotter and gained thermal energy. What was the source of this energy?
A)the tidal pull of a passing star
B)gravitational potential energy released by inward-falling material
C)nuclear energy from the interior
D)energy released by radioactive decay

Accepted Answer

The source of the energy was the gravitational potential energy released as the Sun contracted. As the material fell inward, it converted potential energy into thermal energy, heating up the Sun's interior.

Question 7

The protosun became a full-fledged star when:
A)thermonuclear fusion reactions began at its center.
B)the temperature began to rise at its center.
C)it became hot enough to emit light and heat.
D)planetary formation was complete.

Accepted Answer

The protosun became a full-fledged star when thermonuclear fusion reactions began at its center, causing it to emit light and heat. This is the process by which stars produce their energy and is the defining characteristic of a star. The other options may be part of the process leading up to the protosun becoming a star, but only thermonuclear fusion reactions mark the transition to a full-fledged star.

Question 8

An early theory of solar system formation was the tidal hypothesis-the idea that a star passed close enough to the Sun to draw out a long filament of material that then condensed to form the planets and other solar system bodies. Why was this theory discredited?
A)A star this close to the Sun would form a binary star system rather than the single star we actually have.
B)Such a long filament would be thickest near the Sun and would form the largest planets there.
C)Stars move so slowly that any star this close to the Sun four and a half billion years ago would still be in the solar vicinity.
D)Tidal forces strong enough to pull a filament out of the Sun would also be strong enough to cause it to disperse before it could condense into planets.

Accepted Answer

Tidal forces strong enough to pull a filament out of the Sun would also be strong enough to cause it to disperse before it could condense into planets.

Question 9

The planetary system was probably formed from three different categories of material with different condensation temperatures (the temperature at which the material melts): gases, ices, and rocks. Which is the correct order of these materials, in increasing condensation temperature?
A)rocks, gases, and ices
B)rocks, ices, and gases
C)gases, rocks, and ices
D)gases, ices, and rocks

Accepted Answer

Gases condense at the lowest temperatures, followed by ices, and rocks require the highest temperatures to condense.

Question 10

Which of the these types of material has the highest condensation temperature in the planetary system?
A)hydrogen
B)rocks and dust grains
C)nitrogen gas
D)gases such as methane, ammonia, and water vapor

Accepted Answer

Rocks and dust grains have the highest condensation temperature in the planetary system as they solidify at much higher temperatures than gases like hydrogen, nitrogen gas, methane, ammonia, and water vapor.

Question 11

The most common ices in the early solar nebula were:
A)hydrogen and helium.
B)water ice and carbon dioxide.
C)hydrogen, methane, and ammonia.
D)water ice, methane, and ammonia.

Accepted Answer

Water ice, methane, and ammonia are the most common ices in the early solar nebula, based on current scientific understanding. These ices would have formed at the low temperatures and high densities found in the outer regions of the solar nebula, where the gravity of the forming Sun and other protoplanets was weaker. Meanwhile, hydrogen and helium would have been present throughout the entire nebula, but are not considered "ices" in the same sense as water or methane. Carbon dioxide, while present in the solar nebula, would have been less common than water ice and methane based on the temperatures and pressures of the nebula at the time.

Question 12

Which substances form ice in the outer solar system?
A)carbon dioxide and iron oxides
B)hydrogen and helium
C)water, carbon dioxide, and minerals rich in iron, silicon, magnesium, and sulfur
D)water, ammonia, and methane

Accepted Answer

Water, ammonia, and methane are known to form ice in the outer solar system. This is because these substances have low freezing points and can exist as solids at the low temperatures found in the outer solar system.

Question 13

Various ices condense at temperatures less than 300 K. What is the smallest distance from the Sun in the early solar nebula at which these ices would have condensed to form solid particles? (See Figure 8-10 of Universe, 11th ed.)
​
 ​
A)2 au
B)5 au
C)1 au
D)1.5 au

Accepted Answer

The answer of Various ices condense at temperatures less than...

Question 14

In the early solar nebula, iron sulfide condensed into solid form at a temperature of about 750 K. What is the smallest distance from the Sun at which this would have happened? (See Figure 8-10 of Universe, 11th ed.)
​
 ​
A)0.5 au
B)1.6 au
C)0.2 au
D)0.9 au

Accepted Answer

The answer of In the early solar nebula, iron sulfide...

Question 15

What is the process of chemical differentiation?
A) the separation of different chemical compounds into different regions of the solar nebula; e.g., rocky grains in the inner nebula, icy grains in the outer nebula
B) the sinking of heavy material to the center of a planet or other object and the rising of lighter material toward the surface
C) the condensation of different chemical compounds at different temperatures and therefore at different times-iron first, rock next, and ices last
D) a separation of different chemical compounds into different types of grains in any given part of the solar nebula; e.g., grains of ice, rock, and iron

Accepted Answer

Chemical differentiation refers to the process by which heavy materials sink to the center of a planet or other object while lighter materials rise toward the surface. This process occurs due to differences in density between the materials.

Question 16

The reason most of the terrestrial planets have dense, iron cores is because:
A)iron solidifies at the highest temperatures, so the iron core condensed first from the solar nebula. The rocky material then condensed directly onto the iron core as the nebula cooled.
B)terrestrial planets were initially molten or partially molten, and the iron sank to the center.
C)iron is magnetic, so there was a rapid accretion of iron dust grains into a core, followed by a slow accretion of rocky grains.
D)iron solidifies at the highest temperatures, so the iron core condensed first from the solar nebula. Rocky planetesimals then formed as the nebula cooled further, and gradually impacted onto the iron core.

Accepted Answer

Terrestrial planets were initially molten or partially molten, and the iron sank to the center due to its higher density. This process is known as differentiation.

Question 17

According to modern theories, one significant difference between the formation of the terrestrial and jovian planets is that:
A)both formed by accretion of planetesimals, but the jovian planets became massive enough to attract gas onto them directly from the solar nebula.
B)both formed by accretion of rocky and icy planetesimals, but the terrestrial planets were close enough to the Sun that almost all of the ice escaped back to space after the planets formed.
C)the terrestrial planets formed close to the Sun where there was lots of rock but no ice, whereas the jovian planets formed far from the Sun, where there was lots of hydrogen and ice but no rocky material.
D)the terrestrial planets formed by accretion of planetesimals, whereas the jovian planets formed from streamers of hot gas that shot out of the protostar.

Accepted Answer

Modern theories suggest that both the terrestrial and jovian planets formed by accretion of planetesimals. However, the jovian planets were able to attract gas directly from the solar nebula due to their greater mass, which allowed them to accumulate gas quickly before the nebula dispersed. In contrast, the terrestrial planets were not massive enough to attract gas directly, and so their growth was limited to the solid planetesimals in their vicinity. This led to the formation of small, rocky planets with thin atmospheres, while the jovian planets grew much larger and acquired thick atmospheres dominated by hydrogen and helium.

Question 18

How are many of the satellites of the jovian planets thought to have formed?
A)They are small planets in their own right but were captured by the jovian planets early in the solar system's history.
B)They are fragments of one large satellite orbiting around each of the planets.
C)They are from a disk of material around the planet, similar to the way the planets formed around the Sun.
D)They are from material thrown off the planet when one or more large planetesimals or small planets collided with it.

Accepted Answer

Many of the satellites of the jovian planets are thought to have formed from a disk of material around the planet, similar to the way the planets formed around the Sun. This is supported by observations of the regularity and alignment of some of these satellites' orbits around their respective planets.

Question 19

The environment where the jovian planets initially formed contained all these ingredients except one. Which was the exception?
A)rocks
B)metals
C)ices (water, methane, and ammonia)
D)liquids (water and ammonia)

Accepted Answer

The jovian planets formed in an environment rich in rocks, metals, and ices (such as water, methane, and ammonia), but not in liquid form due to the cold temperatures in the outer parts of the solar system where these planets originated. Liquids like water and ammonia would have been in the form of ice due to the low temperatures, not in their liquid states.

Question 20

How do we explain the relatively low mass of Mars, which is much smaller than Earth or Venus?
A)Mars was fully formed in the outer regions of the solar system and migrated inward to its present orbit well after most planetesimals had disappeared. Thus, it did not grow further.
B)Mars was flung out of the still-molten Earth.
C)The early migration of Jupiter to the present location of Mars's orbit cleared away the planetesimals, which might have enlarged Mars after it formed somewhat later.
D)At some time early in the solar system, Mars and Jupiter exchanged orbits-after Jupiter had already swept up all the planet-building materials from Mars's present orbit.

Accepted Answer

The early migration of Jupiter to the present location of Mars's orbit cleared away the planetesimals, which might have enlarged Mars after it formed somewhat later. This made it difficult for Mars to gather more mass and grow larger like Earth or Venus.

Quiz 8: Comparative Planetology II: the Origin of Our Solar System

How did the temperature of the solar nebula develop?

Which of these statements is an example of Kelvin-Helmholtz contraction?

The most likely mechanism for the solar system's formation appears to be:

To be accepted as a reasonable picture of the formation of the solar system, the nebular hypothesis must explain all of the these statements except one. Which is the exception?

In a rotating physical system (e.g., a star formation region or a skater) , what happens to the rotation rate (or angular speed) when the mass of the system condenses toward the center of rotation?

As the early Sun got smaller in a Kelvin-Helmholtz contraction, its interior became hotter and gained thermal energy. What was the source of this energy?

The protosun became a full-fledged star when:

An early theory of solar system formation was the tidal hypothesis-the idea that a star passed close enough to the Sun to draw out a long filament of material that then condensed to form the planets and other solar system bodies. Why was this theory discredited?

The planetary system was probably formed from three different categories of material with different condensation temperatures (the temperature at which the material melts) : gases, ices, and rocks. Which is the correct order of these materials, in increasing condensation temperature?

Which of the these types of material has the highest condensation temperature in the planetary system?

The most common ices in the early solar nebula were:

Which substances form ice in the outer solar system?

Various ices condense at temperatures less than 300 K. What is the smallest distance from the Sun in the early solar nebula at which these ices would have condensed to form solid particles? (See Figure 8-10 of Universe, 11th ed.)

In the early solar nebula, iron sulfide condensed into solid form at a temperature of about 750 K. What is the smallest distance from the Sun at which this would have happened? (See Figure 8-10 of Universe, 11th ed.)

What is the process of chemical differentiation?

The reason most of the terrestrial planets have dense, iron cores is because:

According to modern theories, one significant difference between the formation of the terrestrial and jovian planets is that:

How are many of the satellites of the jovian planets thought to have formed?

The environment where the jovian planets initially formed contained all these ingredients except one. Which was the exception?

How do we explain the relatively low mass of Mars, which is much smaller than Earth or Venus?