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Transcript
The Gas Giants Astronomy 311 Professor Lee Carkner Lecture 16 Quiz 2 Next Wednesday, October 17 Covers terrestrial planets Lectures 9-15 Will consist of matching, multiple choice and short answer type questions Bring pencil and calculator Gas Giant Basics The 4 largest planets of the solar system are the gas giants Missions to the Outer Planets 1972 Pioneer 10 - 1973 Pioneer 11 -1977 Voyager 1 -1977 Voyager 2 -1989 Galileo -1997 Cassini - 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 Voyager 2’s Grand Tour 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 Orbits Orbital radii for the outer planets range from ~5-30 AU 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) Densities The gas giants have very low densities Average density (kg/m3) Jupiter: Saturn: Uranus: Neptune: For comparison Earth’s density is 5515 Composition The gas giants have a low density because they are made up mostly of hydrogen and helium the 2 lightest elements Total composition Surface and Atmosphere The gas giants do not have a real “surface” Atmospheric Features Clouds Bands Storms Jupiter’s Great Red Spot Neptune’s Great Dark Spot Hurricane on Earth Saturn’s Atmosphere Traveling Through the Solar System 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 Internal Structure of Jupiter Moons Number of satellites (larger than 10 km) Range in size from Ganymede (larger then Mercury) to small pieces of rock Moon Properties Satellites tend to be composed of rock and ice Many have rocky cores and icy surfaces The satellites are very diverse: Jupiter’s Satellites Saturn’s Satellites Rings All of the gas giants have rings of small particles Rings consist of material that has fallen inside the Roche limit Saturn’s A Ring Differences Between the Gas Giants Jupiter and Saturn are larger ,warmer and have more distinct cloud features 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 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
