Transcript 16gasgiants2s

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
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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
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Used gravity of each planet to change
orbit to get to the next
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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
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Sizes of the Gas Giants
Gas giants are all very large compared to the
terrestrial planets
Jupiter and Saturn about 10 Earth diameters
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Uranus and Neptune about 4 Earth diameters
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The gas giants contain 99% of the mass of the solar
system (not including the Sun)
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Densities
The gas giants have very low densities
Average density (kg/m3)
Jupiter:
Saturn:
Uranus:
Neptune:
For comparison Earth’s density is 5515
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Composition
The gas giants have a low density because they are
made up mostly of hydrogen and helium the 2
lightest elements
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Total composition
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Surface and Atmosphere
The gas giants do not have a real
“surface”
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Atmospheric
Features
Clouds
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Bands
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Storms
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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
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Gas giants also have a magnetic field
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Internal Structure of Jupiter
Moons
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Number of satellites (larger than 10 km)
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Range in size from Ganymede (larger then
Mercury) to small pieces of rock
Moon Properties
Satellites tend to be composed of rock
and ice
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Many have rocky cores and icy surfaces
The satellites are very diverse:
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Jupiter’s Satellites
Saturn’s Satellites
Rings
All of the gas giants have rings of small particles
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Rings consist of material that has fallen inside the
Roche limit
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Saturn’s A Ring
Differences Between the Gas
Giants
Jupiter and Saturn are larger ,warmer
and have more distinct cloud features
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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