1. The Gas Giants Astronomy 311 Professor Lee Carkner Lecture 16

2. Which of the following is not a distinguishing feature of meteorites? a)A dark outer crust b)Widmanstatten Patterns c) Long parallel grooves on the surface d)Thumbprint-like depressions on the surface e)Small glassy inclusions

3. Where do iron meteorites come from? a)A very high energy collision of two stony meteorites b)The Kuiper belt c)Near the orbit of Mercury d)A large, differentiated asteroid that got broken up e)The collision that made the Moon

4. Gas Giant Basics  The 4 largest planets of the solar system are the gas giants    All have small cores and large hydrogen outer layers  The gas giants have no real surface, all we see is atmosphere

5. Missions to the Outer Planets  1972 Pioneer 10 --  first spacecraft to the outer planets  1973 Pioneer 11 -- Jupiter/Saturn flyby  1977 Voyager 1 -- Jupiter/Saturn flyby  1977 Voyager 2 –  1989 Galileo -- Jupiter orbiter and probe  1997 Cassini --  arrived 2004, currently taking data

6. Voyager 2  Launched August 20 1977   Only mission to Uranus or Neptune  Used gravity of each planet to change orbit to get to the next   Is still taking data on the edge of the solar system

7. Voyager 2’s Grand Tour

8. 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

9. Orbits   Compare to 0.4-1.5 AU for the inner planets   Orbital periods are also much larger (12-165 years)

10. Sizes of the Gas Giants  Gas giants are all very large compared to the terrestrial planets   Jupiter a little larger   Uranus a little larger   Jupiter itself contains 71%  Volume and mass go as radius cubed

11. Densities   Average density (kg/m 3 )  Jupiter: 1330  Saturn: 700  Uranus: 1300  Neptune: 1760   Saturn is less dense than water (it floats)

12. Composition  The gas giants have a low density because they are made up mostly of hydrogen and helium, the 2 lightest elements   Hydrogen is the lightest and most abundant element in the universe (1 proton + 1 electron)  Total composition    ~5% heavier elements (methane, ammonia, water vapor etc.)

13. Atmospheric Features  Clouds   small amounts of trace elements may produce the colors  Bands   adjacent bands move in opposite directions  Storms   some are very long lived (e.g. Great Red Spot)

14. Odyssey to Jupiter Earth Jupiter at Conjunction Spacecraft Least Energy Orbit Jupiter at Opposition Spaceship Direct Boost

15. Structure   Degree of oblateness depends on mass distribution   Gas giants also have strong magnetic fields  Must have conducting liquid interiors

16. Internal Structure of Jupiter

17. Moons   Number of satellites (larger than 10 km)  Jupiter -- 16  Saturn -- 18  Uranus -- 27  Neptune -- 13   Including the very small ones, about 160 total

18. Moon Properties  Satellites tend to be composed of rock and ice    The satellites are very diverse:   Titan has a denser atmosphere than the Earth  Europa may have a liquid water ocean

19. Rings  All of the gas giants have rings of small particles   The rings of the other planets are made of smaller darker particles and were only discovered by spacecraft   This is the region where the tidal force from the planet is greater than the gravitational force holding the object together

20. Differences Between the Gas Giants   Uranus and Neptune are smaller, cooler and have less distinct cloud features 

21. Next Time  Read 11.1-11.4, 11.6

22. 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

23. 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