21st Century Astronomy

Laura Kay, Stacy Palen, George Blumenthal

Chapter 10

Worlds of Gas and Liquid-The Giant Planets - all with Video Answers

Educators

Chapter Questions

Problem 1

The following steps lead to convection in the atmospheres of giant planets. After (a), place (b)-(f) in order.
a. Gravity pulls particles toward the center.
b. Warm material rises and expands.
c. Particles fall toward the center, converting gravitational energy to kinetic energy.
d. Expanding material cools.
e. Thermal energy heats the material.
f. Friction converts kinetic energy to thermal energy.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 2

Deep in the interiors of the giant planets, water is still a liquid even though the temperatures are tens of thousands of degrees above the boiling point of water. This can happen because
a. the density inside the giant planets is so high.
b. the pressure inside the giant planets is so high.
c. the outer Solar System is so cold.
d. space has very low pressure.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 3

Assume you want to deduce the radius of a planet in our Solar System as it occults a background star when the relative velocity between the planet and Earth is $30 \mathrm{km} / \mathrm{s}$. If the star crosses through the middle of the planet and disappears for a total of 26 minutes, what is the planet's radius?
a. $3,000 \mathrm{km}$
b. $23,000 \mathrm{km}$
c. $15,000 \mathrm{km}$
d. $5,000 \mathrm{km}$

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 4

Neptune's existence was predicted because
a. Uranus did not seem to obey Newton's laws of motion.
b. Uranus wobbled on its axis.
c. Uranus became brighter and fainter in an unusual way.
d. some of the solar nebula's mass was unaccounted for.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 5

Which of the giant planets has the most extreme seasons?
a. Jupiter
b. Saturn
c. Uranus
d. Neptune

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 6

The magnetic fields of the giant planets
a. align closely with the rotation axis.
b. extend far into space.
c. are thousands of times stronger at the cloud tops than at Earth's surface field.
d. have an axis that passes through the planet's center.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 7

An occultation occurs when
a. a star passes between Earth and a planet.
b. a planet passes between Earth and a star.
c. a planet passes between Earth and the Sun.
d. Earth passes between the Sun and a planet.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 8

Occultations directly determine a planet's
a. diameter.
b. mass.
c. density.
d. orbital speed.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 9

The chemical compositions of Jupiter and Saturn are most similar to those of
a. Uranus and Neptune.
b. the terrestrial planets.
c. their moons.
d. the Sun.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 10

Individual cloud layers in the giant planets have different compositions. This happens because
a. the winds are all in the outermost layer.
b. the Coriolis effect only occurs close to the "surface" of the inner core.
c. there is no convection on the giant planets.
d. different volatiles freeze out at different temperatures.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 11

The Great Red Spot on Jupiter is
a. a surface feature.
b. a storm that has been raging for more than 300 years.
c. caused by the interaction between the magnetosphere and Io.
d. about the size of North America.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 12

Uranus and Neptune are different from Jupiter and Saturn in that
a. Uranus and Neptune have a higher percentage of ices in their interiors.
b. Uranus and Neptune have no rings.
c. Uranus and Neptune have no magnetic field.
d. Uranus and Neptune are closer to the Sun.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 13

What could have caused the planets to migrate through the Solar System?
a. gravitational pull from the Sun
b. interaction with the solar wind
c. accreting gas from the solar nebula
d. gravitational pull from other planets

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 14

Zonal winds on the giant planets are stronger than those on the terrestrial planets because
a. they have more thermal energy.
b. the giant planets rotate faster.
c. the moons of giant planets provide additional pull.
d. the moons feed energy to the planet through the magnetosphere

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 15

A "hot Jupiter" gets its name from the fact that
a. its temperature has been measured to be higher than Jupiter's.
b. it is located around a much hotter star than the Sun.
c. it has very high density, and therefore its temperature is high.
d. it orbits very close to its central star.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 16

Describe how the giant planets differ from the terrestrial planets.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 17

Jupiter's chemical composition is more like that of the Sun than Earth's is. Yet both planets formed from the same protoplanetary disk. Explain why they are different today.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 18

What can be learned about a Solar System object when it occults a star?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 19

What drives the zonal winds in the atmospheres of the giant planets?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 20

Compare the sequence of events in the Process of Science Figure in this chapter with the flowchart of the Process of Science Figure in Chapter 1. Redraw the flowchart, incorporating each of the events leading to the discovery of Uranus as examples in the appropriate boxes.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 21

None of the giant planets are truly round. Explain why they have a flattened appearance.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 22

What is the source of color in Jupiter's clouds? Uranus and Neptune, when viewed through a telescope, appear distinctly bluish green in color. What are the two reasons for their striking appearance?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 23

Which of the giant planets have seasons similar to Earth's, and which one experiences extreme seasons?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 24

Jupiter's core is thought to consist of rocky material and ices, all in a liquid state at a temperature of $35,000 \mathrm{K}$. How can materials such as water be liquid at such high temperatures?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 25

Explain how astronomers measure wind speeds in the atmospheres of the giant planets.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 26

What is the Great Red Spot?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 27

Jupiter, Saturn, and Neptune radiate more energy into space than they receive from the Sun. What is the source of the additional energy?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 28

When viewed by radio telescopes, Jupiter is the second-brightest object in the sky. What is the source of its radiation?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 29

What creates auroras in the polar regions of Jupiter and Saturn?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 30

How might migration of the outer giant planets affect the sizes and orbits of the inner planets?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 31

Figure 10.1 shows two different sets of pictures of the outer planets. What is the difference between Figure 10.1 a and Figure $10.1 \mathrm{b} ?$

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 32

Figure $10.9 \mathrm{d}$ shows the winds on Neptune. The graph, however, does not cover the full planet. Is this likely to mean that the wind speed is zero where there is no white line or that the wind speed is unknown where there is no white line? Explain your reasoning.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 33

What creates metallic hydrogen in the interiors of Jupiter and Saturn, and why do we call it metallic?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 34

Use Figure 10.15 to estimate the radius of Io's plasma torus in terms of the radius of Jupiter. Convert this value to kilometers, and then look up the answer on the Internet. How close did you get with your simple measurement?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 35

The Sun appears 400,000 times brighter than the full Moon in Earth's sky. How far from the Sun (in astronomical units) would you have to go for the Sun to appear only as bright as the full Moon appears in Earth's nighttime sky? How does the distance you would have to travel compare to the semimajor axis of Neptune's orbit?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 36

Uranus occults a star at a time when the relative motion between Uranus and Earth is $23.0 \mathrm{km} / \mathrm{s}$. An observer on Earth sees the star disappear for 37 minutes 2 seconds and notes that the center of Uranus passed directly in front of the star.
a. On the basis of these observations, what value would the observer calculate for the diameter of Uranus?
b. What could you conclude about the planet's diameter if its center did not pass directly in front of the star?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 37

Jupiter's equatorial radius $\left(R_{\text {Jup }}\right)$ is $71,500 \mathrm{km}$, and its oblateness is $0.065 .$ What is Jupiter's polar radius $\left(R_{\text {Polar }}\right) ?$ (Oblateness is given by $\left[R_{\text {Jup }}-R_{\text {Polar }}\right] / R_{\text {Jup }}$.)

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 38

Ammonium hydrosulfide (NH,HS) is a molecule in Jupiter's atmosphere responsible for many of its clouds. Using the periodic table in Appendix 3 , calculate the molecular weight of an ammonium hydrosulfide molecule, where the atomic weight of a hydrogen atom is 1. (Recall from Working It Out 9.1 that the weight of a molecule is equal to the sum of the weights of its component atoms.)

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 39

Jupiter is an oblate planet with an average radius of $69,900 \mathrm{km},$ compared to Earth's average radius of $6,370 \mathrm{km}$.
a. Given that volume is proportional to the cube of the radius, how many Earth volumes could fit inside Jupiter?
b. Jupiter is 318 times as massive as Earth. Show that Jupiter's average density is about one-fourth that of Earth's.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 40

The tilt of Uranus is $98^{\circ} .$ From one of the planet's poles, how far from the zenith would the Sun appear on summer solstice?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 41

A small cloud in Jupiter's equatorial region is observed to be at a longitude of $122.0^{\circ}$ west in a coordinate system rotating at the same rate as the deep interior of the planet. (West longitude is measured along a planet's equator toward the west.) Another observation, made exactly 10 Earth hours later, finds the cloud at a longitude of $118.0^{\circ}$ west. Jupiter's equatorial radius is $71,500 \mathrm{km}$. What is the observed equatorial wind speed, in kilometers per hour? Is this wind from the east or west?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 42

The equilibrium temperature for Saturn should be 82 K, but the observed temperature is $95 \mathrm{K}$. How much more energy does Saturn radiate than it absorbs?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 43

Neptune radiates 2.6 times as much energy into space as it absorbs from the Sun. Its equilibrium temperature (see Chapter 5) is $47 \mathrm{K}$. What is its true temperature?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 44

Compare the graphs in Figures $10.8 \mathrm{a}$ and b. Does atmospheric pressure increase more rapidly with depth on Jupiter or on Saturn? Compare the graphs in Figures $10.8 \mathrm{c}$ and d. Does pressure increase more rapidly with depth on Uranus or on Neptune? Of the four giant planets, which has the fastest pressure rise with depth? Which has the slowest?

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 45

Using Figure $10.8,$ find the temperature at an altitude of $100 \mathrm{km}$ on each of the four giant planets.

Jheremiah Simon

Jheremiah Simon

Numerade Educator

Problem 46

Go to the Cassini website (http://saturn.jpl.nasa.gov). Its final mission is scheduled for late 2016 to $2017 .$ Click on "News." What discovery was reported in a recent news release about Saturn (not about the rings or moons)? Why is this discovery important?

Rodger Claar

Numerade Educator

Problem 47

Another website for Cassini images is found at http://ciclops .org. What do the most recent images of Saturn show? What wavelengths were observed? Are the pictures shown in false color, and if so, why? Why are these images important?

Zachary Warner

Numerade Educator

Problem 48

a. Go to websites for the NASA Juno mission (http://www. nasa.gov/mission_pages/juno and http://missionjuno.swri edu), a spacecraft that was launched in 2011 and is scheduled to arrive at Jupiter in $2016 .$ What are the science goals of the mission? Examine the mission's trajectory. Why did it loop around the Sun and pass Earth again in 2013 before heading to Jupiter? Why is there a plaque dedicated to Galileo Galilei on the spacecraft?
b. What are the main instruments for this mission? Are there any data yet? Have any discoveries been reported?

Rodger Claar

Numerade Educator

Problem 49

Go to the website for the Voyager 1 and 2 missions (http:// voyager.jpl.nasa.gov), which collected data on all four of the giant planets more than two decades ago.
a. Where are the spacecraft now? Click on "Images \& Video." These are still the only close-up images of Uranus and Neptune. What was learned about these planets?
b. Click on the icon of "The Golden Record," and then on the right, look at scenes, greetings, music, and sounds from Earth. Suppose you were asked to make a new version of the Golden Record, a playlist to send on an upcoming space mission to outside of the Solar System. What would you include in one or more of those categories?

Lottie Adams

Numerade Educator

Problem 50

Go to the Extrasolar Planets encyclopedia (http://exoplanet. eu/catalog/).
a. Under "Mass," look for a super-Jupiter planet with a mass significantly larger than that of Jupiter. How far is it from its star-is it a hot Jupiter? Click on the planet name-how was it discovered? If a radius is given, is it more or less dense than Jupiter? Click twice on "Mass" to get a list in descending order-what is the most massive super-Jupiter in the catalog?
b. Under "Mass," click on "M $_{\text {Jup " }}$ so it changes to "M $_{\text {Earth }} " ;$ do the same under "Radius" so it shows "R $_{\text {Earth }}$ " Look for a "Super-Earth." What is its radius? How was it detected? Is there an estimated Mass-ifso, what is its density compared with that of Earth? Is it a hot or cold super-Earth?

Joseph Petrullo

Joseph Petrullo

Numerade Educator