Transcript Ice Giants
Ice Giants 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 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. Uranus gravitational pull Sun Neptune 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 Axial Tilt • • • • • • • • Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune 0° 177° 23° 25° 3° 27° 98° 30° tidal lock to sun reversed tidal lock to sun How does one explain this? 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 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 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