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

Mars

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

the sun looks like a basketball and the earth looks like a pindot

What planet is this, and how do you know?

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

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

jupiter looks like a basketball and earth looks like a grape

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

a comet

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 law of conservation of energy

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

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

4

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?

2 billion years

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:

4 days

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

It is made mostly of rock and ice.

According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?

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

According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?

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

Which planet has the highest average surface temperature, and why?

Venus, because of its dense carbon dioxide atmosphere

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.

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

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 0.25 kilogram of the radioactive substance remaining.

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 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 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?

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?

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?

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?

Planetary systems should generally have all planets orbiting in nearly the same plane.





Planetary systems should be common.





Jovian planets always form farther from their star than terrestrial planets.





Other planetary systems should have the same two types of planets: terrestrial and jovian.

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.

Hydrogen and helium gas,hydogen 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.

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.

hydrogen compounds, rock, metals

terrestrial planets

accreted from planetesimals,surfaces dramatically altered during the heavy bombardment

Jovian planets

accreted from icy planetesimals, ejected icy planetesimals that are now Oort cloud comets, formed in regions cold enough for water to freeze, large moons formed in surrounding disks of material, formed in a region of a solar system with lower orbital speeds.

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

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

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

none

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

anywhere between 0.3 and the frost line

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

rocks, metals, and ices

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 nearer the planetary system's star than any jovian planets.

Compared to terrestrial planets, jovian planets are __________.

more massive and lower in average density

Which planet is approximately halfway between Pluto's orbit and 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?

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.

The composition of the solar nebula was 98%

hydrogen and helium.

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.

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.

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

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

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