Saturn Ring Structure - Outline

1. Saturn Ring Structure - Outline F B D C A E and G rings not shown

2. Saturn Rings Backlit Exaggerated Color Earth C E G F B D A

3. Rings, Ringlets, Details Rings in gaps between rings A, B and F rings

4. Ring Details

5. C Ring (Left) and B Ring (Right) Details

6. Ring Details (D, C, B, A, F)

7. Enceladus and Saturn’s E Ring • Enceladus is spraying ice into space • These chunks go into orbit around Saturn • These form the E ring Enceladus

8. Ripples in the Rings • Each radius orbits at a different speed • As small moons pass ring particles, their orbits are distorted • Their orbits wobble slightly • Net effect: they move away from the small moon • Moons clear gaps around themselves Moon:Daphnis

9. Shepherd Moons Pandora • Pairs of moons can keep a ring between them • Very narrow rings usually have a pair of shepherd moons • Saturn’s F-ring is kept in place by Prometheus and Pandora Q. 54: Narrow Rings Prometheus

10. Jupiter’s Rings • Faint and dark • Mostly microscopic dust • Some portions are dust from known moons • Remainder probably dust from undiscovered moons

11. Uranus’s Rings • 13 known rings • Very dark material • Shepherd moons for bright  ring • Small amounts of dust between rings • Composition varies by ring, but typically • Ice with dark covering? • Typical size object around 1 m • Source: Probably collisionally shattered moon(s)

12. Shepherd Moons for Uranus’s  Ring Shepherd Moons  ring

13. Neptune’s Rings • 5 known rings • Very dark material • Mostly tiny dust • Probably shattered moons?

14. The Dregs of the Solar System Dwarf Planets August 24, 2006: IAU defines a planet Goes around a star Is big enough to be round Is much bigger than all other things in its neighborhood combined Confirmed Dwarf Planets: Ceres Pluto Haumea Makemake Eris A dwarf planet satisfies 1 and 2, but not 3 A small solar system body satisfies only 1

15. Outline of the Dregs • The Kuiper Belt • Pluto and its moon Charon • Eris • The Oort cloud • Comets • Meteoroid showers • Asteroids • Ceres • Meteorites

16. Comets/Kuiper Belt – How We Know • Multiple missions to Comet Halley (’86) • ICE • Suisei • Sakigake • Vega 1 • Vega 2 • Giotto • Stardust Mission • Wild-2 (’04), sample return (’06), Tempel 1 (’11) • Deep Impact mission • Tempel 1 (with impactor, ’05), Hartley 2 (’10) • Rosetta – Orbiter and Lander • Churyumov- Gerasimenko (’14-’16) • New Horizons • Pluto/Charon flyby (’15) • Ultima Thule flyby (January ’19) • Telescopes • Ongoing

17. Recent Missions to Kuiper Belt / Comets New Horizons Rosetta

18. The Kuiper Belt • Icy bodies, some rock/dust • Mostly beyond Neptune • Too sparse to coalesce • More than 1000 known • Probably about 100,000 larger than 100 km • Size: • All are smaller than our Moon • Six or so known with diameter > 1000 km

19. Kuiper Belt: Location

20. Pluto and its Moons 1 medium moon • Charon 4 known small moons Styx Hydra Kerberos Nix

21. Pluto & Charon: Size, Orbit, Rotation • Pluto half the size of Mercury • Charon half the size of Pluto • Close together • Tidally locked to each other Actual separation Pluto Charon

22. Pluto Composition • Large rocky core • Frozen ice (mostly water) mantle • Frozen nitrogen layer • Very thin atmosphere • Changes seasonally • Mostly nitrogen

23. Pluto Surprises • Pluto has mountains on its surface • Almost certainly made of water ice • Pluto has almost no craters on it! • Young surface • Difficult to explain

24. Ultima Thule • After passing Pluto system, New Horizons was redirected to examine a small Kuiper belt object near its path • An obscure KBO called Ultima Thule was chosen as the target • 33 km in length • On Jan. 1, 2019, New Horizons made its closest approach and took images • These pictures are still being returned

25. Eris Eris • Eris has one known small moon • Orbit more eccentric than Pluto • Orbit more inclined than Pluto Eris Dysnomia

26. Largest Kuiper Belt Objects • Eris and Pluto would be considered large moons • Composition similar to many outer moons Moon Q. 55: Mass of Kuiper Belt Objects

27. Kuiper Belt Objects • Planetismals • Formed in outer solar system • Never coalesced - too few • Giant Planets toss them around • Tossed out - join the Oort Cloud • Tossed in - become short period comets

28. Kuiper Belt and Short Period Comets Neptune • Neptune distorts orbit • Object becomes a comet Kuiper Belt

29. The Oort Cloud • Icy bodies, some rocks/dust • Billions of objects • Hundreds or thousands of AU from the Sun • Passing stars can change their orbits • Swing in to become long period comets

30. Comets

31. Comet McNaught

32. Comet Kohoutek

33. Comet Hale-Bopp

34. Comet Swan

35. Comet Classification • Short Period comets • Less than 200 years • Started in the Kuiper Belt • Long Period comets • More than 200 years • Started in the Oort Cloud

36. Parts of Comets • Icy nucleus - some dust • 1-50 km is diameter • Only part that exists far from Sun • Coma • Size of the Sun! • Expanding gasses plus dust fromthe heated nucleus • Easiest part to see • Tail(s) • 1 AU in length! • Dust tail – charged specks of dust • Ion tail – individual charged particles Q. 56: Size of Comet’s Parts

37. Parts of Comets

38. Comet Tails • Solar wind pushes particles away from the Sun • It points behind when inbound • It points ahead when outbound

39. Comet West Dust Tail Ion Tail Coma

40. Parts of Comets Ion Tail Dust Tail Coma

41. Comet Haley

42. Comet Haley Dust Tail Coma Ion Tail

43. Nucleus of Comet Haley

44. Nucleus of Churyumov- Gerasimenko