AY 101 Chapter 6 review

Venus and Uranus are exceptions

Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun?

it heated up and spun up.

As the solar nebula collapsed under its own gravity,

collisions between particles made the particles go in more-or-less the same direction

As the solar nebula collapsed, it became a disk because

the law of conservation of angular momentum. The law of conservation of angular momentum holds that the cloud's total angular momentum should stay unchanged as it shrinks in size. Like a spinning ice skater bringing in her arms, the cloud's rotation speed therefore increases as it shrinks. More technically, recall that angular momentum is proportional to velocity times radius; therefore, as the radius shrinks, the velocity of rotation must increase in order to keep the product of velocity times radius unchanged.

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

all

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

Comets

Leftover ice-rich planetesimals are called

fairly circular and in the same plane.

Planetary orbits in our solar system are:

rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds to freeze only in the o

The temperature of the protoplanetary disk allowed

Unusually large moons form in giant impacts, which are relatively rare events. Our Moon is thought to have formed as a result of a giant impact in which a Mars-size object slammed into the young Earth. The fact that this happened to 1 of the 4 terrestrial planets in our solar system suggests that it is reasonable to find the same thing on a similar fraction of the terrestrial planets in another system. But it would be very surprising to find it happening to 6 out of 6 terrestrial planets.

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?

The Sun

generates energy deep in its core through the fusion of hydrogen into helium

Jupiter

has a famous storm known as the Great Red Spot.

Mercury

has a greater difference in temperature between its day and night sides than any other world.

Neptune

has a large moon, Triton, that almost certainly once orbited the Sun independently.

Earth

has a single moon that is surprisingly large compared to its planet.

Venus

has a surface hot enough to melt lead as a result of an extremely strong greenhouse effect.

Uranus

has an axis tilt that gives it very extreme season

Mars

has no surface liquid water today, but shows clear evidence of such water in the distant past.

1/32

1/32 inch

600

627.3051 rounded to 1 significant digit is _____

627.3

627.3051 rounded to 4 significant digits is____

630

627.3051 rounded to the nearest 10 is______

627.31

627.3051 rounded to the nearest 100 is

18,000- The calculation is 18,000 + 32, since 2012 is 32 years after 1980. The first number (18,000) is precise to the nearest 1000, while the second (32) is precise to the nearest 1. Following the rule for addition and subtraction, the answer should be rounded to the nearest 1000, since that is the precision of the least precise number. Therefore, even though 32 years passed since the book was written, the time since the ice age remains 18,000 years.

A book written in 1980 states that the peak of the last ice age occurred 18,000 years ago. Therefore, in 2012, the peak had occurred _____ years ago.

1

A measurement of 0.005 microgram has ____ significant digit(s).

5

A measurement of 1.0005 microgram has

6

A measurement of 2.00000×1052.00000×105 centimeters has _____ significant digit(s)

1

A measurement of 200,000 centimeters has ___ significant digit(s)

4

A measurement of 700.1 seconds has ___ significant digit(s)

1

A measurement of 700700 seconds has ____ significant digit(s)

4.5 billion years

About how old is the solar system?

These condensation regions explain the makeup of objects at different distances from the Sun. In the inner regions of the solar nebula, where temperatures were high, only metal and rock could condense, which is why the inner planets ended up being made of metal and rock. Farther out, hydrogen compounds could condense into ices, which is why comets and outer solar system moons contain large amounts of ice. And because hydrogen compounds are more abundant than metal or rock, some of the solid objects in the outer solar system grew so large that their gravity could pull in hydrogen and helium gas, which explains how the jovian planets formed.

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.

All the planets orbit the Sun in the same direction and in nearly the same plane. The orbits of the planets reflect the rotation pattern of the flat, rotating disk in which they formed.

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?

Planetary systems should generally have all planets orbiting in nearly the same plane. Jovian planets always form farther from their star than terrestrial planets. Planetary systems should be common. Many extrasolar planets should fall into the terrestrial or jovian categories. We expect all solar systems to form in similar ways from collapsing gas clouds and therefore to share basic features, such as the planets all orbiting in the same direction and nearly the same plane. We also expect planets to form similarly through accretion, with planets that form near a star tending to be terrestrial in nature and planets that form farther away tending to be jovian; however, as you'll learn in later chapters, the details of planetary formation allow for additional types of planets beyond just those two categories. We do not expect particulars that are probably coincidental, such as the precise numbers of planets, to be the same in different solar systems.

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?

Uranium-235

Compare the graph in (Figure 1) to (Figure 2), which shows the decay of potassium-40. Which element is more radioactive (undergoes radioactive decay more quickly)?

all the planets formed in a rotating, disk-shaped nebula. The nebular theory predicts that all planets should be born on orbits going in the same direction and in nearly the same plane.

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 __________.

this might have happened in our own solar system if it had taken longer for the solar wind to clear the solar nebula. If the solar nebula had remained for a longer time, accretion could have continued for a longer period of time, forming larger ice-rich objects. In fact, we cannot yet be sure that this didn't happen in our solar system: Eris, which is slightly larger than Pluto, was discovered only in 2005, and it's possible that even larger ice-rich objects remain to be discovered.

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 _________.

Consistent with theory: Beyond its jovian planets, a star has two ice-rich objects as large as mars. A Star has 20 planets Of a star's 5 terrestrial planets, 1 has a moon as large as Earth's moon. A star is surrounded by a disk of gas but has not planets. Not consistent with theory: A star's 4 jovian planets formed in its inner solar system and its 4 terrestrial planets formed farther out. All 6 of a star's terrestrial planets have a moon as large as Earth's moon. 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.

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.

there would not be any planets orbiting the Sun.

If the solar nebula initially had no angular momentum,

been similar in composition to Earth, with a much smaller mass than the real Jupiter

Suppose the solar nebula had been too warm for ices to condense anywhere. If a planet had still formed at Jupiter's location, it most likely would have

with a higher abundance of hydrogen compounds and larger size

Suppose the solar nebula had cooled much more before the solar wind cleared away the remaining gas. In that case, the terrestrial planets likely would have ended up

our Moon formed when a Mars-size object collided with the young Earth.

The "giant impact hypothesis" refers to the idea that ___________

hydrogen and helium

The composition of the solar nebula was 98%

510- We find the amount of money that must be collected per person by dividing the dollar amount by the population: dollar amount per person=$41,500,00082,000 persons=$506.097561dollar amount per person=$41,500,00082,000 persons=$506.097561 According to the rule for multiplication and division, we must round this answer to the number of significant digits in the number with the fewest significant digits in the calculation. Because the population is given with only 2 signification digits, we round the answer to 2 significant digits as $510.

The government in a town of 82,000 people plans to spend $41.5 million this year. Assuming all this money must come from taxes, what is the average number of dollars that the city must collect from each resident

hydrogen compounds are more abundant than rocks and metals so that beyond the frost line the gravity of large ice planetesimals could capture the abundant light gases

The inner planets are small and rocky and the outer planets are mostly large and gaseous because

rocks, metals, and ices. Because ices could condense only beyond the frost line, we expect jovian planets to form only beyond the frost line. Note that many extrasolar planets appear to be jovian but are located close to their stars, leading scientists to suspect that these planets migrated inward after originally forming beyond the frost lines of their star systems.

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

1.99×10301.99×1030 kilograms-- The given mass of the Sun is precise to the nearest 0.01×10300.01×1030 kilograms, while the given mass of Earth is precise to the nearest 0.01×10240.01×1024 kilograms. Because 10301030 is one million times as large as 10241024, Earth's mass is given in this problem with a precision one million times as great as the Sun's mass. The mass of the Sun is therefore the least precise number in the calculation, so the answer should have the same precision as the given mass of the Sun. Earth's mass is much smaller than this precision, and therefore it does not affect the answer.

The mass of the Sun is 1.99×10301.99×1030 kilograms and the mass of Earth is 5.97×10245.97×1024 kilograms. Therefore, the combined mass of the Sun and Earth is __________.

Knowing this ranking order is useful, but even more important is to recognize the vast differences in abundance: Hydrogen and helium gas constituted about 98 percent of the mass in the solar nebula. Most of the rest was hydrogen compounds, which were nearly three times as abundant as rock and metal combined.

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.

In fact, hydrogen and helium gas never condense into solid form under the conditions that exist in interstellar clouds such as the solar nebula. Continue on to Part C to see how the condensation temperatures of the other materials explain why different materials condensed in different regions of the young solar system.

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.

the law of conservation of energy. The law of conservation of energy tells us that energy must always be conserved. Because the cloud has much more gravitational potential energy when it is large in size than when it is small, its gravitational potential energy must be transformed into other forms of energy, such as heat (thermal energy), as it shrinks in size.

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

Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole. Particles in the collapsing cloud inevitably collide with one another. These collisions allow particles to exchange angular momentum, but their total angular momentum must be conserved. Therefore, many collisions result in an averaging out of the angular momentums of individual cloud particles, a process that brings their orbits into approximately the same plane.

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?

the same cloud of gas and dust in which the Sun formed.

The planets in our solar system are thought to have come from

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. 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.

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?

Many stars should have planets.

We expect a scientific theory to be able to make predictions that can be tested. Which of the following is a prediction of the nebular theory that has been verified by observations?

There are clear patterns to the rotation and orbits of large bodies in the solar system. There are a few notable "exceptions to the rules." There are vast numbers of asteroids and comets. Planets fall into two major categories.

What are four key features of our solar system that any theory of solar system formation must be able to explain?

hydrogen and helium

What is Jupiter's main ingredient?

none. Although all the materials were present in gaseous form, the innermost regions (within about the inner 0.3 AUAU) of the newly forming solar system was too warm for even rocks or metals to condense into solid flakes.

What substances existed as solid flakes within the innermost regions (within about the inner 0.3 AUAU) of the solar system before planets began to form?

rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form. As described in the video and your textbook, all the materials of the solar nebula were present in the inner region, but it was too hot for any of them to condense. As a result, they were all in gaseous form.

What substances were found in the innermost regions (within about the inner 0.3 AUAU) of the solar system before planets began to form?

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

What's unusual about our Moon?

anywhere between the innermost regions (within about the inner 0.3 AUAU) and the frost line. Terrestrial planets are made mostly of metal and rock and therefore formed in the region in which it was cool enough for metal and rock to condense but still too warm for hydrogen compounds to condense into ices. This means the region between the innermost regions (within about the inner 0.3 AUAU) and the frost line.

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

collapse, condensation, accretion

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

concentrating denser materials nearer the Sun

Which of the following did not occur during the collapse of the solar nebula?

It's a volcanic rock nearly a billion years old.

You find a mysterious rock on the ground and determine that 60%% of its uranium-235 has been converted into lead-207. What is the most likely origin of the rock, based on its radiometric age?

Saturn

is orbited by at least two geologically active moons: Titan and Enceladus.

Eris

is similar in size to Pluto and also considered a dwarf planet.

Pluto

was studied up close in 2015 by the New Horizons spacecraft.