General Astronomy The Solar System The Outer Worlds Many slides are taken from lectures by Dr David...
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Transcript of General Astronomy The Solar System The Outer Worlds Many slides are taken from lectures by Dr David...
General AstronomyThe Solar System
The Outer Worlds
Many slides are taken from lectures by Dr David Wood, San Antonio College
The PlanetsIn order of increasing distance from the Sun:
– Mercury– Venus– Earth– Mars– Jupiter– Saturn– Uranus– Neptune
My Very Excellent Mother Just Served Us Nachos
Inner Planets
Outer Planets
Planets
We continue by looking at the Outer Planets and attempt to categorize their main features:
JupiterSaturnUranusNeptune
Jupiter's Statistics Eccentricity 0.048
Orbital period 11.9 yrs
Orbital Radius 5.20 AU
Inclination 1° 18'
Radius 71,492 km
Mass (Earth Masses) 318
Density 1.33 g/cm³
Escape velocity 57.5 km/s
Rotation 10 hours
Tilt of Axis (Obliquity) 3.08°
Albedo 0.51
Mean surface temperature
125 K
Shoemaker – Levy 9• May 1993 – Carolyn & Eugene Shoemaker,
& David Levy find comet with 21 fragments orbiting Jupiter
• July 20, 1994 – Comet Shoemaker – Levy 9 impacts Jupiter with Fragment “G” leaving a scar larger than Earth in diameter
• Only impact event ever directly witnessed by human beings
Saturn's Statistics
Eccentricity 0.056
Orbital period 29.5 yrs
Orbital Radius 9.53 AU
Inclination 2° 30'
Size 60,268 km
Mass (Earth Masses) 95.2
Density 0.69 g/cm³
Escape velocity 35.4 km/s
Rotation 10 hours
Tilt of Axis 26.7°
Albedo 0.50
Mean surface temperature
95 K
Gas Giant StructureHydrogen is converted from is
gaseous to its liquid and metallic forms under pressure
Galileo probe discovered a liquid water layer in Jupiter’s atmosphere
Original seeds of planets form core
Gas Giant Atmospheres• Jupiter
– Composition is primarily 75% H2 and 24% He– Galileo probe detected a liquid water layer– We see cloud tops that swirl and change with lightning– Banded structure
• Belts are dark bands that move vertically downward and horizontally eastward
• Zones are bright bands that move vertically upward and horizontally westward
– Great Red Spot• Stable for > 350 years• Counter-clockwise rotation in southern hemisphere• High pressure system• Resides between a belt and a zone and feeds off them
• Saturn– Composition is primarily 79% H2 and 19% He– Banded structure with belts and zones but more
subdued than Jupiter– Clouds are more spread out and smog in between– Faster equatorial wind speeds than Jupiter (1000 km/hr)
Uranus' Statistics
Eccentricity 0.046
Orbital period 84 yrs
Orbital Radius 19.2 AU
Inclination 46'
Size 25,559 km
Mass (Earth Masses) 14.6
Density 1.56 g/cm³
Escape velocity 21.9 km/s
Rotation 18 hours
Tilt of Axis 98°
Albedo 0.66
Mean surface temperature 60 K
Neptune's Statistics
Eccentricity 0.010
Orbital period 165.1 yrs
Orbital Radius 30.1 AU
Inclination 1.8°
Size 24,764 km
Mass (Earth Masses) 17.3
Density 2.27 g/cm³
Escape velocity 24.4 km/s
Rotation 24 hours
Tilt of Axis 29.6°
Albedo 0.62
Mean surface temperature 60 K
Ice Giant Structure
Hydrogen is converted from is gaseous to its liquid form under pressureCannot create enough pressure for metallic hydrogenAlmost certainly liquid water layers deep in planets…perhaps surrounding the coresDiamond rain or snow?Original seeds of planets form core
Ice Giant Atmospheres• Uranus
– Still primarily hydrogen & helium– Methane ice crystals provide bluish
color– Belts and zones are very faint– Severe seasons due to large axis tilt– Recent Hubble observations show
new storms raging as seasons as winter hemisphere sees sunlight
• Neptune– Surprisingly active– Belts and zones visible to Voyager– Great Dark Spot and Little Dark Spot
were/are giant storms– Great Dark Spot vanished between
1989 and 1995– Highest wind speeds in solar system
Comparing Jovian PlanetsJupiter Saturn Uranus Neptune
Composition
GaseousLiquid hydrogen
Metallic hydrogen
Rock – metal core
GaseousLiquid hydrogen
Metallic hydrogen
Rock – metal core
GaseousLiquid
hydrogenH2O, CH4, NH3
Rock?
GaseousLiquid hydrogenH2O, CH4, NH3
Rock?
Differentiated
Yes Yes Yes Yes
Atmosphere75% Hydrogen
24% Helium75% Hydrogen
24% HeliumMethane Methane
Magnetic Field
Enormous! Large Large Large
# Moons 60t 30 23 8
# Rings 17 (major)
Thousands (minor)
8 7 (ring arcs)t 21 moons have been discovered in 2003 alone
Magnetic Fields• Jupiter
– Metallic hydrogen generates enormous magnetic field
– Tilted 10° to rotation axis– Io produces a small “hole” in magnetic
field
• Saturn– Metallic hydrogen generates large
magnetic field– Not as large as Jupiter’s field since less
metallic hydrogen– Tilted 0° to rotation axis
• Uranus– Metallic hydrogen is not present, so
core compounds generate magnetic fields
– Tilted 60° to rotation axis
• Neptune– Metallic hydrogen is not present, so
core compounds generate magnetic fields
– Tilted 46° to rotation axis
Moons• Jupiter – 60 moons
– Galilean Moons are Io, Europa, Ganymede, Callisto
– 11 moons discovered by Galileo in 2000
• Saturn – 30 moons– Titan possesses large atmosphere– Mimas is “Death Star” moon
• Uranus – 23 moons– Named primarily after
Shakespearean characters– Miranda possesses unique geology– 21st moon discovered in Oct. 2002– 22nd & 23rd discovered Sept 2003
• Neptune – 11 moons– Triton possesses a weak
atmosphere– 6 new moons discovered by
Voyager 2 in 1989
Rings• Jupiter
– 1 ring– Visible only in backlighting– Discovered in 1979
• Saturn– 7 major rings– Thousands of minor rings– Radial spokes – still
unknown– Discovered in 1600s
• Uranus– 8 thin rings– Discovered in 1977
• Neptune– 7 minor ring arcs– Discovered in 1989