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

2. Saturn Rings Backlit
Exaggerated Color
Earth E G B F C 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 Moon: Daphnis
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 Q. 54: Narrow Rings Prometheus
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

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 Styx Hydra Kerberos Nix 1 medium moon Charon
4 known small moons
Styx
Kerberos
Hydra
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 Dysnomia Eris has one known small moon
Orbit more eccentric than Pluto
Orbit more inclined than Pluto
Eris
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 distorts orbit
Object becomes a comet
Kuiper Belt
Neptune

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 Q. 56: Size of Comet’s Parts 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 from the 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