Class 24: Uranus, Neptune, Pluto
Solar System Distances
39 AU 30 AU *Planets not to scale Distances not to scale 19 AU
Uranus: A Global Perspective
Differences Earth Uranus
• Size (radius) 6738 km 4x Earth • Mass 6x1024 kg 145 Earth • Density 5.5 g/cm3 1.3 g/cm3
• Atmosphere 78%N2 21%O2 84%H 14%He 2%CH4 (methane) • Surface temperature 20°C -200°C • Rotation 1 day -17.9 hours
1 Exploring Uranus
Herschel
Uranus moons
Voyager 2 Hubble Space Telescope
Uranus’s Interior
(1)
(2)
core
Axis of Rotation
23.5°
98 °
Earth Uranus
2 Atmosphere & Magnetic Field
magnetic axis
visible
rotation axis 60°
The Rings of Uranus
dust bands
The Moons of Uranus
Oberon (2nd largest) Titania (largest)
r ≈ 789 km
Umbriel
Miranda
Puck
Ariel
3 Neptune: A Global Perspective
Differences Earth Neptune • Size (radius) 6378 km 3.9x Earth • Mass 6x1024 kg 171 Earth • Density 5.5 g/cm3 1.6 g/cm3
• Atmosphere 78%N2 21%O2 84%H 14%He 2%CH4 (methane) • Surface temperature 20°C -210°C • Rotation 1 day 16 hours
Exploring Neptune
Adams
Le Verrier
Galle
Voyager 2 HST
Neptune’s Interior
(1) H, He, CH4
(2)
H2O, CH4, NH3
core
4 Neptune’s Atmosphere & Clouds
Neptune clouds
cloud bands Scooter
The Great Dark Spot
Voyager 2
Voyager 2
Voyager 2 GDS changes
Neptune’s Rings & Moons
twisted ring?
faint rings
Nereid Triton
5 A Parting Look
Pluto: A Global Perspective
Similarities Earth Pluto • Moon 1 - Moon 1 - Charon
Differences
• Size (radius) 6378 km 0.2x Earth • Mass 6x1024 kg 0.002x Earth • Density 5.5 g/cm3 0.4x Earth
• Atmosphere 78% N2 21% O2 probably N2, thin • Surface temperature 20°C -230°C • Rotation 1 day 6.4 days
* Pluto’s orbit is VERY eccentric (sometimes inside Neptune)!
Exploring Pluto
Tombaugh, Lowell Observatory
Photo 1 Photo 2 planetary symbol
Charon
6 Pluto’s Interior
(1)
core
Pluto: Is it a planet?
Rose Center for Earth & Space, New York City
Pluto - Charon System
112°
7 Pluto and Charon from Hubble
Bright/dark regions: differences in methane/nitrogen frost cover
New Horizons Mission
• Lanch window: January 2006
• Interplanetary cruise: 2007 - 2015
• Pluto-Charon encounter: 2015
Uranus
• Satellites 27 • Size (radius) 25,900 km • Density 1.3 g/cm3 • Orbit 84.01 years • Rotation -17.9 hours
• Atmosphere 83% H , 15% He, 2% CH4 (methane) • Surface pressure 1.2 atm • Surface temperature -200°C (at cloud surface)
8 Neptune
• Satellites 13
• Size (radius) 24,746 km
• Density 1.6 g/cm3
• Orbit 165 years
• Rotation 17 hr, 15 min.
• Atmosphere 95% CO2, 3% N2 • Surface pressure 0.01 atm
• Surface temperature -210°C
Pluto
• Satellites 11
• Size (radius) 1137 km
• Density 2.05 g/cm3
• Orbit 248 years
• Rotation -6.4 days
• Atmosphere N2? • Surface pressure 1.2 atm
• Surface temperature -193°C
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