4-4 The Outer Planets

The Solar System – Course 3

Vocabulary

Gas Giant - The name often given

to the outer planets Jupiter,

Saturn, Uranus, and Neptune.

Ring – A thin disk of small ice

and rock particles surrounding

a planet.

My Planet Diary pg. 154

Predicting a PlanetIn the 1840s, astronomers were puzzled. Uranus didn’t move as expected, based on the theory of gravity. Astronomers John Couch Adams and Urbain Leverrier independently hypothesized that Uranus was being affected by another planet’s gravity. They calculated where this planet

should be. Another astronomer, Johann Galle, aimed his telescope at the place Leverrier predicted. On September 23, 1846, he discovered the new planet—Neptune.

Communicate- Work with a partner to answer the question.What science skills did the astronomers use when they discovered

Neptune?_____________________________________________________________________________________________________________________________________________________________

What Do the Outer Planets Have in Common? Pg. 154The four outer planets are much larger and more

massive than Earth, and they do not have solid surfaces. Because these four planets are so large, they are often called gas

giants. The gas giants all contain hydrogen and helium.

Composition- Jupiter and Saturn are made mostly of hydrogen and helium. Uranus and Neptune are made also of ammonia and methane. All the gas giants exert a very strong gravitational force which keeps gases from escaping, and forms thick atmospheres.

Even though they are called gas giants, most of the material in these planets is actually liquid.

The outer layers are very cold because they are far from the sun. Temperatures increase greatly within the planets.

What Do the Outer Planets Have in Common? Pg. 154

Moons and RingsAll the gas giants have many moons. Neptune has 13 & Jupiter has 60!The moons vary in size from tiny balls of rock and ice barely a km

across to moons larger than Mercury. Some moons are so large they have their own atmospheres!

In addition, all have many moons and are surrounded by a set of rings. A ring is a thin disk of small particles of ice and rock. They do not have solid surfaces. If you could visit them, you wouldn’t have a solid place to stand. Saturn’s rings are the largest and most complex.

Assess Your Understanding pg. 155

I get it! Now I know that the gas giants all _____________________

______________________________________________________

JUPITER Pg. 156

Jupiter is the largest and most massive planet. Its mass is about 2½ times that of all the other planets combined!

Jupiter’s Atmosphere-made of mainly hydrogen and helium-One notable feature of Jupiter’s atmosphere is its Great Red Spot, a storm

that is larger than Earth.

Jupiter’s Structure-Astronauts think Jupiter has a dense core of rock and iron at its center. -A thick mantle of hydrogen and helium surround the core.-Because of the weight of Jupiter’s atmosphere, the pressure at the core is

estimated to be 30 million times greater than the pressure at Earth’s surface.

Jupiter’s Moons-Italian astronaut Galileo Galilei discovered Jupiter’s largest moons in 1610.The moons are: Io, Europa, Ganymede, and Callisto.

The Moons of Jupiter pg. 1571. Io is not icy, unlike most of Jupiter’s moons. It may have as many as 300 active volcanoes. The eruptions fromthose volcanoes constantly change themoon’s surface.

2. Europa is covered with ice. ThereMay be liquid water below the ice- andIf there’s water, there might be life.

3. Ganymede is Jupiter’s largest moon.It is larger than Mercury! Its surface is divided into dark and bright areas.

4. Callisto is second to Ganymede in size, but has less ice. It has the most craters of an of Jupiter’s moons.

SATURN Pg. 159

-Saturn is the 2nd largest planet. It has a thick atmosphere of mainly hydrogen and helium.

Saturn’s RingsSaturn has the most spectacular rings of any planet.

The rings are made of chunks of ice and rock, each traveling in its own orbit around Saturn.

Saturn’s MoonsSaturn’s largest moon, Titan, is larger than the planet Mercury, and

has features that look as if they were formed by flowing liquid. A few scientists think that Titan might support life.

URANUS pg.160

Uranus is 4x the diameter of Earth but is still much smaller that Jupiter and Saturn. Uranus is twice as far from the sun as Saturn, so it is much colder. It looks blue-green because of methane traces in its atmosphere. Uranus has thin, flat rings surrounding it, but they are darker in color than Saturn’s rings.

Uranus’s Moons

Its five largest moons have icy, cratered surfaces. The craters show that the rocks form space have hit the moons. They also have lava flows on their surfaces. Recently several more moons have been discovered, for a total of at least 27.

A Tilted PlanetUranus’s axis of rotation is tilted at an angle of about 90

degrees from the vertical.

Viewed from Earth, Uranus rotates from top to bottom—not side to side.

Uranus - Figure 5 pg. 160

A Sideways PlanetHow do day and night at Uranus's equator change as Uranus revolves around the sun?

Compare and Contrast-

How do day and night at Uranus’s equator change as Uranus revolves around the Sun?____________________________________________________________________________________________________________________

NEPTUNE Pg. 161

Neptune is a cold, blue planet. Its atmosphere contains visible clouds. Neptune’s blue color comes from methane in the atmosphere. Its interior is hot from energy left from its formation. As the energy rises, it produces clouds and storms in the atmosphere.

Neptune’s Atmosphere

Neptune was photographed in 1989 by Voyager 2 and showed a Great Dark Spot about the size of Earth. It was probably a giant storm, but it didn’t last long. Images taken 5 years later showed the spot was gone.

Neptune’s Moons

Astronomers have discovered at least 13 moons orbiting Neptune. The largest moon is Triton, which has a thin atmosphere.

Apply it! Pg. 161Congratulations! You’ve earned enough AU in your travels to qualify

for a free mission to one planet or moon of your choice!

1. Make Judgments- Which planet or moon do you choose? List three reasons for your choice. ________________________

________________________________________________________________________________________________

2. Pose Questions- What is one question you would want your mission to answer? ________________________________

________________________________________________

Assess Your Understanding pg. 161

1. Compare and Contrast- List one distinguishing feature for each outer planet.

___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

I get it! Now I know that the outer planets differ in ____________

___________________________________________________________________________________________________