1. Uranus in the Sky

2. Uranus As seen by Voyager

3. Uranus Highlights Accidently discovered in March 1781 by William Herschel  Fits Bode’s Law! Visited by Voyager 2 in 1986 Suspicious lack of internal heat – probably leads to bland appearance of atmosphere Composition: ~75% H, ~25% he Probably a small rocky core (3% of total mass) Ice-rock “slush” interior Bluish color derives from methane which is a good absorber of red light

4. Discovery of Uranus William Herschel at left discovered Uranus by accident. He used the 6-inch telescope at right, which he built himself.

5. Featureless Planet

6. Atmosphere of Uranus

7. Interior View of Uranus and Neptune

8. Oddball Properties of Uranus Magnetic field: –About same Earth’s field –BUT, dipole inclined by 60 o and offset from planet center by 1/3 of R U Caught during a field reversal??? Tilt: –Extreme tilt remains unexplained –Each pole spends 42 years in light and then 42 in darkness

9. The Odd Magnetic Field of Uranus

10. Rings of Uranus Discovered March 1977 during a stellar occultation Nine narrow rings ranging in width 10-100 km Thin and faint with particles of size cm to several meters Dust fills inter-ring gaps –Requires replenishment Moons Cordelia and Ophelia act to shepherd some rings

11. Ring Discovery from Occultation

12. Uranus Ring System

13. The IR View

14. Share Question Seasons on Uranus are a) as long as Uranus' year b) non-existent c) one fourth of Uranus' year, or about 20 Earth years long d) four times Uranus' year, or about 320 Earth years long

15. Discovery of Neptune oBy 1821, the orbit of Uranus clearly deviated from its predicted path which couldn’t be explained by influence of known planets.  Evidence for another planet! o“Discovered” by Adams (English, late 1845) and Leverrier (France, 1846) independently o1 st observed by Galle (German) on 9/23/1846

16. Neptune

17. Scale of Neptune

18. Voyager at Neptune

19. Neptune with Moons

20. Neptune’s Atmosphere oBelts oZones oClouds oWind - 2200kph at the equator oStorms - ovals and Great Dark Spot oGreat Dark Spot: High pressure region in S. hemisphere, about size of Earth By 1994, Spot had disappeared, and a new Dark Spot had formed at N. latitudes (HST)

21. Multi-Wavelength Neptune

23. Neptune’s Great Dark Spot

24. Neptunian Weather

25. Neptune’s Magnetic Field Surface field similar to Earth’s in strength Magnetic axis tilted by 47 o Dipole offset by 1/2 R N Unlikely that both Uranus and Neptune are undergoing field reversals at the same time!

26. Summary of Magnetic Fields

27. Internal Energy of Neptune Uranus lacks convection and therefore storms Neptune does have internal heat like Jupiter and Saturn (Neptune emits 60% more than absorbs) A MYSTERY! How can Uranus and Neptune be so different when so similar in size and mass? [Inhibition of convection in Uranus?]

28. Rings of Neptune Voyager 2 found rings, although there had been previous evidence for them Dark and faint Little intergap dust Rings likely composed of dust themselves Bright arcs in out ring (effect of shepherding?)

29. Rings of Neptune

30. Schematic of Neptune’s Rings