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 2’s 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/m 3 )  Jupiter:  Saturn:  Uranus:  Neptune:  For comparison Earth’s 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. Jupiter’s Great Red Spot

14. Neptune’s Great Dark Spot

15. Hurricane on Earth

16. Saturn’s 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. Jupiter’s Satellites

23. Saturn’s 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. Saturn’s 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 Earth’s Moon)  All of the outer planets (not just Saturn have ring systems)  rings composed of small particles  Ring properties different for each planet