The Outer Solar System

How does a thin planetary ring retain its shape?

Small moons orbiting just inside and outside the rings shepherd the ring particles.

The surface age of Triton is thought to be about 100 million years. What is the evidence for such an age determination?

the density of impact craters

What gives Saturn's rings their beautiful structure?

the gravitational influence of Saturn's moons on the ring particles

The discoveries of Uranus, Neptune, and Pluto all came long after the death of Isaac Newton. How was Newton involved in the discovery of a new planet?

ALL It was the application of Newtonian gravity to the problem of the orbit of Uranus that led to the discovery of Neptune. It was with a reflecting telescope (the type invented by Newton) that the planet Uranus was discovered. It was through perceived perturbations by Newtonian gravity on the orbit of Neptune that a search for a ninth planet was begun that eventually resulted in the discovery of Pluto. It was with a reflecting telescope (the type invented by Newton) that the planet Uranus was discovered and it was through perceived perturbations by Newtonian gravity on the orbit of Neptune that a search for a ninth planet was begun that eventually resulted in the discovery of Pluto.

Why do some astronomers think Pluto is a member of the Kuiper belt rather than a planet?

ALL its size and mass its composition its location

With respect to the moons of Saturn, select all of the correct statements from the following list.

All of Saturn's moons are a mixture of rock and ice.Titan is the only solar system moon with a substantial atmosphere.Some of Saturn's moons may have been captured asteroids or Kuiper belt objects.Smaller moons of Saturn have cracks and smooth areas that suggest past geologic activity.

What evidence do we have that Jupiter is primarily composed of hydrogen and helium rather than rock?

All of these choices are correct.

The surface of which of Jupiter's moons is seen in the figure?

Callisto

Which list below ranks the planets (Jupiter, Saturn, Uranus, and Earth) in order of increasing mass, from left to right?

Earth, Uranus, Saturn, Jupiter

Which list below ranks the planets (Jupiter, Saturn, Uranus, and Earth) in order of increasing size, from left to right?

Earth, Uranus, Saturn, Jupiter

What evidence do we have that the surface of Europa is young and active?

Europa has very few impact craters and the icy crust of Europa is highly reflective.

How can small worlds like Triton have atmospheres, when larger objects like Ganymede have none?

Farther from the sun, it is colder and easier to retain gases and most of the atmospheric gases sublimate from ice on the surfaces of the objects.

How does Ganymede differ from Callisto?

Ganymede is differentiated and Callisto is not.

Using the table above, which list below ranks the Galilean satellites of Jupiter in order of decreasing size, from left to right?

Ganymede, Callisto, Io, Europa

Why does Europa have few impact craters?

Geological activity has erased them.

Why does Io have no impact craters?

Geological activity has erased them.

Examining the table above, we see that ______ is the most abundant substance in both Jupiter and Saturn.

H2

Examining the table above, we see that ______ is the second most abundant substance in both Jupiter and Saturn.

He

Why would you expect Io to have more impact craters than Callisto?

Io is closer to Jupiter, so it's subject to more potentially impacting objects.

In this image you can see Jupiter's four large moons (from left to right): Io, Europa, Ganymede, and Callisto (also in order of increasing distance from Jupiter). Which of the following is a list of these moons in order from highest density to lowest density?

Io, Europa, Ganymede, Callisto

What evidence do we have that Jupiter has a very hot interior?

It emits 70% more energy at infrared wavelengths than it receives from the sun.

What does it mean when a planet is "oblate?"

Its equatorial diameter is larger than its polar axis and it bulges around the equator.

With respect to the evolution of Jupiter's moon and ring systems, and how Jupiter is different than Earth, select all of the correct statements from the following list.

Jupiter has a small solid core, a deep liquid mantle, and a gaseous atmosphere. There is water in Jupiter's atmosphere .Jupiter has over 10 times the diameter and over 300 times the mass of Earth.

In the 1950s radio telescopes first detected synchrotron radiation from Jupiter. What did this discovery tell us about Jupiter?

Jupiter has a strong magnetic field.

This diagram illustrates a model of Saturn's interior. Why is the metallic hydrogen zone for Saturn smaller than Jupiter's metallic hydrogen zone?

Jupiter has more mass and thus greater gravitational compression at a depth.

How do the differences in the interiors of Saturn and Jupiter affect the planets' magnetic fields?

Jupiter's is stronger than Saturn's.

Which list below ranks the four Jovian planets in order of increasing distance from the sun, from left to right?

Jupiter, Saturn, Uranus, Neptune

The shape of small satellites differ from large satellites. What is the reason for this?

Larger moons have enough mass to gravitationally pull themselves into a spherical shape, and smaller ones do not.

How do the appearance of the leading and trailing sides of some satellites differ?

Leading sides tend to be darker, and trailing sides brighter.

If Neptune had no satellites, would you expect it to have rings?

No; ring material comes from the moons.

How do Saturn's three layers of clouds differ from Jupiter's three layers of clouds?

None of these choices are correct.

Based on whether Pluto really is a planet or if it is something else, select all of the correct statements from the following list.

Pluto is too far away to study in detail from Earth. Pluto's crust is largely ice. Some astronomers suggest that Pluto and Charon are members of the Kuiper belt. When discovered, Pluto was not nearly as massive as it was expected to be.

With respect to the outer planets, select all of the correct statements from the following list.Note that Pluto is now defined as a dwarf planet.

Pluto's characteristics do not fit in with the other outer planets'. Being rich in hydrogen, the large outer planets are low in density. The outer planets (except Pluto) are larger than Earth. All Jovian planets have rings and moon systems.

In which way does Saturn differ from Jupiter?

Saturn has a smaller zone of liquid metallic hydrogen.

This figure shows the orientation of the rotational axis of Uranus relative to its orbital plane throughout its 84-year-long trip around the sun. How do the seasons on Uranus differ from the seasons on Earth?

Seasons on Uranus are 84 times longer and more extreme than on Earth.

With respect to Saturn and its differences with Jupiter, select all of the correct statements from the following list.

Smaller moons "shepherd" particles in the ring system, or keep them in their rings.Some ring particles are small moons that were pulled apart by tidal forces.Although it has the most extensive one, Saturn is not the only planet with a ring system.Being twice as far from the sun, Saturn is much colder than Jupiter, making its atmosphere much less active.Saturn's rings are made mostly of ice particles.

What evidence do we have that Io's crust and lava is mostly silicate rock rather than sulfur compounds?

Some mountains on Io are much higher than any mountains on Earth and much of the lava flowing from Io's volcanoes is hotter than Earth lava.

With respect to Jupiter's family of moons, select all of the correct statements from the following list.

Some of Jupiter's smaller moons are probably captured asteroids. Callisto's old, cratered surface tells us that it has never been geologically active. Ganymede probably was geologically active in the past. Volcanic activity has been observed on lo.

What evidence do we have that Pluto and Charon are made of mixtures of rock and ice?

Spectra show that both bodies have some surface ices and both bodies have a density of 2 grams per cubic centimeter.

What keeps small shepherd moons from breaking apart within the Roche limit of a planet?

The moons must be structurally strong (which means that they are kept from breaking apart by the electrostatic bonds of the moon's material).

Jupiter's ring appears dark in back-scattered light, yet appears bright in forward-scattered light. What does this tell us about the particles that make up Jupiter's ring?

The particles' average diameter is a few micrometers and are most likely dust.

Why is there no liquid metallic hydrogen zone in the interiors of Uranus or Neptune?

The pressure is too low for hydrogen to be metallic.

In this image you can see Jupiter's main ring appear bright in forward-scattered light. What does this indicate about the ring particles in Jupiter's main ring?

The ring particles are about the size of the wavelength of visible light.

What evidence indicates that the rings of Uranus have little dust and the rings of Neptune contain a lot of dust?

The rings of Uranus appear dark in forward-scattered light and the rings of Neptune appear bright in forward-scattered light.

What are the leading and trailing sides of a satellite?

The sides that always face forward and backward to the direction of its orbit around the planet.

How can the cores of Uranus and Neptune have magnetic fields?

Their magnetic fields are believed to be generated by convection in the liquid mantle.

What evidence is there that Neptune's moon Triton is geologically active?

There are few craters and there are cracks in the ice.

The image of Uranus on the left is as it would look to the naked eye. The image on the right is how it would look through a red filter that enhances methane clouds in the northern hemisphere. What do the visible atmospheric features tell you about circulation on Uranus?

There is a very slight belt-zone circulation that can only be seen with computer enhancement.

If Saturn had no moons, what do you suppose its rings would look like? Why is this?

There would be no rings since without moons, there would be no material available to be part of the ring system.

Why are Europa, Ganymede, and Callisto necessary for the continued heating of Io?

These moons periodically tug on Io and keep its orbit elliptical.

The density of Callisto is 1.8 grams per cubic centimeter and that of Ganymede is 1.9 grams per cubic centimeter. What does this suggest about these outer two of Jupiter's four big moons?

These two moons must be made of roughly equal volumes of ice and rock.

Why are the belts and zones on Saturn less distinct than those on Jupiter?

They are deeper inside Saturn's atmosphere.

The mantles of Uranus and Neptune are believed to be which of the following?

They are liquid.

What is the origin of the rings of Neptune?

They are made of debris from impacts on Neptune's moons.

What is the origin of the rings of Uranus?

They are made of debris from impacts on Uranus's moons.

Where do astronomers think the particles being added today to Saturn's rings come from?

They are material ejected from the moons by impacts.

The cores of Uranus and Neptune are believed to be which of the following?

They are solid.

The shape of larger satellites should be spherical, while the smaller ones shouldn't be. Which is a pair of moons that is an example of this?

Titan and Hyperion

How can Titan have a nitrogen-methane atmosphere with a surface pressure 1.5 times that of Earth's atmosphere, whereas the larger and more massive Ganymede has no atmosphere at all?

Titan is farther from the sun and thus colder than Ganymede.

With respect to how Neptune is different from Uranus, and how its rings and moons formed and evolved, select all of the correct statements from the following list.

Triton has a thin atmosphere and may be geologically active. Neptune's largest moon, Triton, has a retrograde orbit, which suggests that it was captured. Neptune's position was predicted before it was discovered. Neptune is similar to Uranus as far as size, mass, composition, and interior structure. This figure shows the

What is peculiar about the orbits of Neptune's moons Triton and Nereid?

Triton's orbit is in the retrograde direction, and Nereid's orbit is large and very elliptical.

In what way is Uranus different than the other Jovian planets?

Uranus has little remaining heat of formation.

With respect to how Uranus is different from Jupiter, and how its rings and moons formed and evolved, select all of the correct statements from the following list.

Uranus is much smaller and less massive than Jupiter. Uranus's appearance is nearly featureless; very bland Uranus has some large moons and rings. Uranus rotates on its side, giving it extreme seasons. This may have been caused by an impact.

Jupiter is more oblate than Earth. Would you expect the other Jovian planets to be more oblate than Earth as well?

Yes. None of them are solid and they all rotate quickly.

What is a zone?

a bright band of clouds in a Jovian planet's atmosphere

What is a belt?

a dark band of clouds in a Jovian planet's atmosphere

What is the Kuiper belt?

a population of small rocky/icy objects mostly beyond the orbit of Neptune

If you piloted a spacecraft to Saturn's moons and wanted to look for a geologically active surface, what factors would you look for?

both smooth and grooved areas and volcanic features

The two requirements for a strong planetary magnetic field are rapid rotation and a convective interior zone composed of an electrically conductive material. Jupiter's rotational period is slightly less than 10 hours. What type of matter fulfills the second requirement?

liquid metallic hydrogen

What difference in the rings of Uranus and Neptune was first revealed in observations from Earth-based telescopes?

the clumpy ring arcs of Neptune

Why is the surface in the above figure so dark?

meteorite dust dirtying the ice

Why are some areas lighter?

more-recent impacts have dug craters deeper into the ice

If you visited Pluto, and observed Charon from Pluto's surface directly overhead when full, where would Charon be in the sky when it was first quarter?

overhead; Pluto and Charon are tidally locked and always face each other

If you visited Pluto, and observed Charon from Pluto's surface directly overhead when full, where would Charon be in the sky when it was new?

overhead; Pluto and Charon are tidally locked and always face each other

If Triton is geologically active, what is its energy source?

radioactive decay in its interior and sunlight

Most of the composition of Pluto and Charon is which of the following?

rock

What is the Roche limit?

the maximum distance from a planet at which planetary rings can exist

If you were to record the spectrum of Saturn and its rings, you should find light from one edge of the rings on the west (right) side of the image red-shifted and light from the other east (left) edge blue-shifted relative to light from the planet itself. This is interpreted as due to ___________.

the orbital motion of the ring particles around Saturn itself

What evidence is there that Pluto and Charon are made of rock and ice?

their densities

What energy source drives the weather that we see on Jupiter?

thermal energy escaping from Jupiter's interior that is still hot from formation