1. The Outer Planets
Chap 16, Sec 4

2. Chap 16 Sec 4 Essential Questions
What characteristics do the gas giants have in common?
What characteristics distinguish each of the outer planets?

3. The Gas Giants

4. The Gas Giants The four outer planets
Jupiter
Saturn
Uranus
Neptune
Much larger & more massive than Earth
Do not have solid surfaces
All are composed mainly of hydrogen & helium
Their gravitational force is much greater than Earth’s because of their massive size
They have thick atmospheres
A lot of the hydrogen & helium inside the planets is liquid because of enormous pressure
Outer layers of the planets are cold because of their distance from the sun, but temperatures increase inside the planets
All have many moons
All have rings
A ring is a thin disk of small particles of ice and rock

5. Jupiter

6. Jupiter The largest & most massive planet Atmosphere:
Its mass is about 2 ½ times all other planets combined
Atmosphere:
Thick atmosphere of mainly hydrogen & helium
The Great Red Spot – a giant storm larger than Earth. Swirling winds blow hundreds of miles an hour, similar to a hurricane, but it has lasted for 350 years and doesn’t appear to be weakening

7. Jupiter Structure: A dense core of rock and iron at the center
The core is surrounded by a thick mantle of liquid hydrogen & helium
Pressure at Jupiter’s core may be 30 million times greater than the pressure at Earth’s surface
Extreme pressure is caused by its thick atmosphere

8. Jupiter’s Moons Remember Galileo discovered the largest four
Many more have been discovered as technology improved – latest count is more than 63
The four largest are all very different from each other and are all larger than our Moon

9. Jupiter’s Largest Moons
Io – its surface is covered with large, active volcanoes. Sulfur gives it an unusual color.
Europa – it has an icy crust and scientists suspect it has an ocean of liquid water underneath the ice
Ganymede – the largest moon in the solar system is larger than Mercury or Pluto
Callisto – has an icy, cratered surface

10. Io

11. Ganymede

12. Europa

13. Callisto

14. Saturn

15. Saturn The second-largest planet
Has a thick atmosphere of hydrogen & helium
Atmosphere has thick clouds and storms – though not as spectacular as those on Jupiter
The least dense planet (less dense than water)
The Voyager probes provided lots of information about Saturn

16. Saturn’s Rings Saturn has the most spectacular rings of any planet
The rings are broad and thin – like a CD
The rings are made of chunks of ice and rock, each traveling in its own orbit around Saturn

17. Saturn’s Moons Saturn is currently known to have more than 60 moons
The largest is Titan
It has a very thick atmosphere (so thick that light can hardly pass through)
There are four other moons that are larger than 1,000 kilometers in diameter

18. Two views of Titan
From Far Away
Very Close Up with special Lens

19. Uranus

20. Uranus
It is about four times the diameter of Earth, but much smaller than Jupiter and Saturn
It is twice as far from the sun as Saturn, so it is much colder
Has a unique blue-green color because of methane gas in its atmosphere
Its rings are thin, flat, and much darker than Saturn’s
It was the first planet discovered since ancient times
Discovered in 1781 by Willam Herschel in England

21. Unique Features of Uranus
In the 1980s (200 years after being discovered) Voyager 2 arrived at Uranus and sent back close-up pictures
It has few clouds, but astronomers calculated it rotated in about 17 hours
Uranus is tilted on its side
It rotated top to bottom instead of side to side like other planets (and its rings and moons rotate around its tilted axis)
Scientists think it was hit by an object billions of years ago that knocked it on its side

22. Uranus’s Moons Uranus has at least 27 moons
Voyager 2 discovered the five largest moons have icy, cratered surfaces and lava flows

23. Neptune

24. Neptune Neptune is similar in size and color to Uranus
It is a blue color because of methane in its atmosphere
Because it is so far from the sun, it is very cold
It has clouds and storms in its atmosphere
Scientists think the clouds and storms are happening because the planet is slowly shrinking and causing the interior to heat up

25. Discovering Neptune
Neptune was discovered by mathematics – astronomers noticed Uranus’s orbit wasn’t the exact path it should be and predicted an unseen planet was disturbing Uranus’s orbit
By 1846 scientists had calculated the orbit of the unseen planet – soon after, Neptune was identified

26. Flying by Neptune
In 1989 Voyager 2 flew by Neptune and photographed the Great Dark Spot (a storm about the size of Earth)
Storms come and go on Neptune which tells us it has an active atmosphere

27. Neptune’s Moons Neptune has at least 13 moons The largest is Triton
It has a thin atmosphere
Its south pole is covered in nitrogen ice

28. Pluto Pluto is not a gas giant
It is much smaller and denser than the outer planets and has a solid surface
Pluto is smaller than our Moon
Pluto is so far from the sun that it takes 240 Earth years to revolve around the sun once
Its orbit is very elliptical and it crosses inside Neptune’s orbit for part of its revolution
Moons
Pluto has at least three. The largest is Charon and is more than half as big as Pluto

29. Dwarf Planets
Dwarf planets are round and orbits the sun, like a planet, but it has not cleared out the neighborhood around its orbit
Dwarf planet classification was created in 2006 when an object larger than Pluto and farther from the sun was discovered
At that time Pluto was reclassified as a dwarf planet and there are two others

30. Video

31. Essential Questions - Answered
What characteristics do the gas giants have in common?
No solid surface
Thick atmosphere made mostly of hydrogen & helium
A set of rings
Very Large & massive
Rotates quickly, revolves slowly

32. 2. What characteristics distinguish each of the outer planets?
Jupiter – largest & most massive planet, Great Red Spot, most moons (63+)
Saturn – second largest planets, best rings, least dense planet
Uranus – blue-green color, rotates on its side
Neptune – blue color, lots of storms
Pluto – solid, rocky surface; no longer a planet