Ice Giants

1
Ice Giants
2
Amateur Discovery

• Classical astronomy observed 5 planets.
• Uranus slow
• Looked like a star
• Uranus was discovered in 1781 by William
  Herschel.
• Confused for a comet
• 84 year period

3
Mathematical Discovery

• Uranus didnt quite match Keplers laws.
• 60 years of its 84 year revolution
• Mathematicians calculated the gravitational pull
  needed by an unknown planet, and then found it -
  Neptune in 1849.

Uranus
gravitational pull
Sun
Neptune
4
Distant Twins

• Uranus
• Seventh planet
• 20 AU from Sun
• 4 times Earth size
• 15 times Earth mass
• 84 year revolution
• 17 hour day
• Water and iron core
• Temperature -190 C

• Neptune
• Eighth planet
• 30 AU from Sun
• 3.8 times Earth size
• 17 times Earth mass
• 165 year revolution
• 16 hour day
• Water and iron core
• Temperature -200 C

5
Axial Tilt

• Mercury 0 tidal lock to sun
• Venus 177 reversed tidal lock to sun
• Earth 23
• Mars 25
• Jupiter 3
• Saturn 27
• Uranus 98 How does one explain this?
• Neptune 30

6
Major Collision

• To be tilted on the side Uranus must have had a
  collision.
• The colliding object must have been huge to
  deflect a planet the size of Uranus (14 times the
  mass of Earth).

before collision
after collision
7
Uranian Clouds

• Uranus has the brightest clouds in the solar
  system.
• Different on the north and south sides
• Long time to see both sides
• Clouds have ices.
• methane, ammonia, and water

8
Neptunian Winds

• Methane makes clouds blue.
• There are massive clouds in the atmosphere and it
  has the fastest winds of any planet.
• Great Dark Spot