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 didn’t quite match Kepler’s 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. Sun Uranus Neptune gravitational pull

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 Mercury0°tidal lock to sun Venus177°reversed tidal lock to sun Earth23° Mars25° Jupiter3° Saturn27° Uranus98°How does one explain this? Neptune30°

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 collisionafter 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