The Gas Giants

1
The Gas Giants

• Astronomy 311
• Professor Lee Carkner
• Lecture 16

2
Gas Giant Basics

• The 4 largest planets of the solar system are the
  gas giants

3
Missions to the Outer Planets

• 1972 Pioneer 10 --
• 1973 Pioneer 11 --
• 1977 Voyager 1 --
• 1977 Voyager 2 --
• 1989 Galileo --
• 1997 Cassini --

4
Voyager 2

• Launched August 20 1977
• Used gravity of each planet to change orbit to
  get to the next
• Is still taking data on the edge of the solar
  system

5
Voyager 2s Grand Tour
6
Gas Giant Facts

• Jupiter
• Diameter 11.21
• Mass 317.83
• Orbital Radius 5.20
• Saturn
• Diameter 9.42
• Mass 95.16
• Orbital Radius 9.54

• Uranus
• Diameter 4.01
• Mass 14.50
• Orbital Radius 19.19
• Neptune
• Diameter 3.88
• Mass 17.20
• Orbital Radius 30.06

• Numbers are relative to the Earth

7
Orbits

• Orbital radii for the outer planets range from
  5-30 AU

8
Sizes of the Gas Giants

• Gas giants are all very large compared to the
  terrestrial planets
• Jupiter and Saturn about 10 Earth diameters
• Uranus and Neptune about 4 Earth diameters
• The gas giants contain 99 of the mass of the
  solar system (not including the Sun)

9
Densities

• The gas giants have very low densities
• Average density (kg/m3)
• Jupiter
• Saturn
• Uranus
• Neptune
• For comparison Earths density is 5515

10
Composition

• The gas giants have a low density because they
  are made up mostly of hydrogen and helium the 2
  lightest elements
• Total composition

11
Surface and Atmosphere

• The gas giants do not have a real surface

12
Atmospheric Features

• Clouds
• Bands
• Storms

13
Jupiters Great Red Spot
14
Neptunes Great Dark Spot
15
Hurricane on Earth
16
Saturns Atmosphere
17
Traveling Through the Solar System
18
Structure

• The gas giants are not perfectly round, they are
  oblate due to rotation
• Degree of oblateness depends on mass distribution
• Gas giants also have a magnetic field

19
Internal Structure of Jupiter
20
Moons

• Number of satellites (larger than 10 km)
• Range in size from Ganymede (larger then Mercury)
  to small pieces of rock

21
Moon Properties

• Satellites tend to be composed of rock and ice
• Many have rocky cores and icy surfaces
• The satellites are very diverse

22
Jupiters Satellites
23
Saturns Satellites
24
Rings

• All of the gas giants have rings of small
  particles
• Rings consist of material that has fallen inside
  the Roche limit

25
Saturns A Ring
26
Differences Between the Gas Giants

• Jupiter and Saturn are larger ,warmer and have
  more distinct cloud features

27
Summary

• Size 4-11 times Earth diameter
• Mass 15-318 Earth masses
• Composition mostly hydrogen and helium
• Atmosphere clouds of methane and ammonia
• also have large, long-lived storm systems and
  oppositely moving bands

28
Summary The Jovian Systems

• The gas giants have extensive satellite systems
• Many moons have icy exteriors with rocky cores
• Some are very large (size of Earths Moon)
• All of the outer planets (not just Saturn have
  ring systems)
• rings composed of small particles
• Ring properties different for each planet