1. 14b. Pluto, Kuiper Belt & Oort Cloud
The Kuiper Belt
Basic characteristics
Resonant Kuiper Belt objects
Classical Kuiper Belt objects
The Oort Cloud

2. Kuiper Belt Objects (KBO’s)
Hypothesized
Gerard Kuiper 1951
Proposed as a source region for short-period comets
Discovered
David Jewitt & Jane Luu 1992
Found 1992 QB1 ~ 42 AU from the Sun
Spectrally very similar to Pluto & Charon
1,352 known KBO’s as of early 2008
Quaoar discovered 4 June 2002
Quaoar measured September 2002
Quaoar announced 7 October 2002
~ 1,300 km in diameter & in a nearly circular orbit
Implications
Pluto & Charon may simply be closest & largest KBO’s
The I.A.U. no longer considers Pluto a [major] planet ! ! !

3. Resonant Kuiper Belt Objects
Three orbital resonances with Neptune
2:3 resonance Plutinos
92 confirmed members Pluto is the naming member
104 possible members
1:2 resonance
14 confirmed members
2:5 resonance
6 confirmed members
Additional resonances are known
6 confirmed members in 6 resonances

4. Resonant TNO Orbits

5. Pluto In Color

6. The Discovery of Hydra & Nix

7. The Largest Plutinos
ThePlutinos_Size_Albedo_Color2.svg/250px-ThePlutinos_Size_Albedo_Color2.svg.png

8. Trans-Neptunian Objects (TNO’s)
TheTransneptunians_73AU.svg/800px-TheTransneptunians_73AU.svg.png

9. Eight Largest Trans-Neptunian Objects

10. Still More Trans-Neptunian Objects
TheTransneptunians_Size_Albedo_Color.svg/600px-TheTransneptunians_Size_Albedo_Color.svg.png

11. The Outer Solar System KBO’s Scattered Disc Objects
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12. Classical Kuiper Belt Objects
Neptune’s influence negligible from 42 to 48 AU
Small-object orbits are essentially undisturbed
About two-thirds of all known KBO’s are here
May be observational bias Close enough to be seen
First discovered KBO was labeled QB1
Classical KBO’s are known as cubewanos “Q-B-1-os”
Two categories
Dynamically cold population
Orbital eccentricity < 0.1
Orbital inclination < 10°
Dynamically hot population
Orbital eccentricity > 0.1
Orbital inclination > 10° & < 30°

13. Eris Basic facts Largest known KBO One moon named Dysnomia
~ 1, km in diameter Highly uncertain
Ninth largest known object in orbit around the Sun
One moon named Dysnomia
Dysnomia
Eris

14. The Orbit of Eris

15. The Öpik-Oort Cloud Hypothesized independently by two astronomers
Ernst Öpik Estonian 1932
Comets originate in a distant spherical cloud
Jan Hendrik Oort Dutch 1950
Comets completely sublimate after a few orbits
Comets have survived to the present time
Basic characteristics
Spherical cloud of long-period comets
~ 50 to 50,000 AU from the Sun
~ 1 light year
~ 25% the distance to Alpha Centauri, the nearest star

16. Some Features of the Öpik-Oort Cloud
Two segments
Inner cloud
Torus distribution
50 to 20,000 AU from the Sun
Source of Halley-type comets
Outer cloud
Spherical distribution
20,000 to 50,000 AU from the Sun
Source of long-period comets
Oort Cloud objects OCO’s
Only two candidates have been identified
Sedna
2000 CR105

17. The Oort Cloud & the Kuiper Belt

18. Candidate Oort Cloud Objects (OCO’s)

19. Sedna Named after Sedna Inuit goddess of the sea Orbital parameters
Discovered in 2003
At the time, the farthest known natural Solar System object
Maximum possible diameter is ~ 75% that of Pluto
Orbital parameters
76.16 AU Perihelion
Visible only when it is closest to the Sun
AU Aphelion

20. Sedna’s Orbit & the Oort Cloud
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