14b. Pluto, Kuiper Belt & Oort Cloud

1. 14b. Pluto, Kuiper Belt & Oort Cloud • Pluto • Basic characteristics • Pluto’s moons • The Kuiper Belt • Basic characteristics • Resonant Kuiper Belt objects • ClassicalKuiper Belt objects • The Oort Cloud • Basic characteristics

2. Pluto Data: Numbers • Diameter: 2,290.km 0.18 . Earth • Mass: 1.0 . 1022 kg 0.002 . Earth • Density: 2.0 . water 0.36 . Earth • Orbit: 5.9 . 109 km 39.53 AU • Day: 6d.09h 17m 51s 0.27 . Earth • Year: 248.6 years 248.6 . Earth

3. Pluto Data: Special Features • Pluto is the farthest planet from the Sun • Pluto is the smallest planet • Pluto has a very thin atmosphere • Pluto is much smaller than the Moon • Pluto has only ~0.18 . the mass of the Moon • Pluto has only ~0.66 . diameter of the Moon • Pluto’s interior likely consists of two layers • An “icy”mantle (~25% of Pluto’s mass) • A “rocky” core (~75% of Pluto’s mass) • Pluto is extremely difficult to observe from Earth • Pluto is extremely small & far from the Sun • Pluto’s moon Charon has ~0.08 .Pluto’s mass

4. Pluto Data (Table 14-5)

5. Pluto’s Amazing Discovery • The reason for a search • Apparent discrepancies in Neptune’s predicted orbit • Actually no unaccounted perturbations of Neptune • The actual search • Percival Lowell • Urged construction of a wide-field astronomical camera • Camera was completed in 1929 • Clyde Tombaugh worked at Lowell Observatory • Discovered Planet X on 18 February 1930 • Announced discovery on 13March1930 • Some obvious problems • Much more dim & small than expected • More highly elliptical orbit than any other planet • More steeply inclined orbit than any other planet

6. Pluto & Charon Are Unique Objects • Planetary patterns • Terrestrial planets • H2 & He poor planets with solid surfaces • Satellites much smaller than parent planets • Jovian planets • H2 & He rich planets with no solid surfaces • Satellites much smaller than parent planets • Pluto’s patterns • Composition • Mixture of ices & rock with a solid surface • Satellite • Closest in mass & diameter of all Solar System pairs

7. The Discovery of Charon • U.S. Naval Observatory • James W. Christy 1978 • Examined existing photographs of Pluto • Noted a bulge on one side • Examination of other photos confirmed a moon • Fundamental characteristics • Orbital period of ~ 6.4 days • < 5 % the Earth-Moon distance • Mutual synchronous axial rotation • One side of Charon always faces Pluto • One side of Pluto always faces Charon

8. Determining Surface Characteristics • An extremely rare alignment • Charon’s line of nodes points directly toward Earth • Throughout the years 1985 to 1990 • Mutual eclipses of Pluto & Charon • Determined most accurate sizes of Pluto & Charon • Determined generalized brightness patterns of Pluto & Charon • The Hubble Space Telescope • Also helpful in determining surface brightness

9. Kuiper Belt Objects (KBO’s) • Hypothesized • Gerard Kuiper 1951 • Proposed a source region for some comets • Discovered • David Jewitt & Jane Luu 1992 • Found 1992 QB1 ~ 42 AU from the Sun • Spectrally very similar to Pluto & Charon • More than 1,000 KBO’s have been discovered • Quaoar discovered June 2002 • Quaoar measured September 2002 • ~ 1,300 km in diameter & in a nearly circular orbit • Implications • Pluto & Charon may be the closest & largest KBO’s • Should we still consider Pluto a planet ? ? ?

10. Computer-Derived Views of Pluto

11. 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 be the closest large KBOs I.A.U. no longer considers Pluto a [major] planet ! ! !

12. Resonant Kuiper Belt Objects • 1:2 resonance Twotinos • 14 confirmed members • 2:3 resonance Plutinos • 92 confirmed members Pluto is the naming member • 104 possiblemembers • 2:5 resonance • 6 confirmed members • 3:5 resonance • 10 confirmed members • 4:7 resonance • 5 confirmed members • Additional resonances are known • 6 confirmed members in 6 resonances

13. http://en.wikipedia.org/wiki/Image:TheKuiperBelt_classes-en.svghttp://en.wikipedia.org/wiki/Image:TheKuiperBelt_classes-en.svg Resonant TNO Orbits

14. http://upload.wikimedia.org/wikipedia/en/3/30/Pluto.jpg Pluto In Color Pluto rotating

15. http://upload.wikimedia.org/wikipedia/commons/3/31/Pluto_system_2005_discovery_images.jpghttp://upload.wikimedia.org/wikipedia/commons/3/31/Pluto_system_2005_discovery_images.jpg The Discovery of Hydra & Nix Pluto's moons

16. http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/ ThePlutinos_Size_Albedo_Color2.svg/250px-ThePlutinos_Size_Albedo_Color2.svg.png The Largest Plutinos

17. Trans-Neptunian Objects (TNO’s) http://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/ TheTransneptunians_73AU.svg/800px-TheTransneptunians_73AU.svg.png

18. http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/EightTNOs.png/800px-EightTNOs.pnghttp://upload.wikimedia.org/wikipedia/commons/thumb/9/91/EightTNOs.png/800px-EightTNOs.png 8 Largest Trans-Neptunian Objects

19. http://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/ TheTransneptunians_Size_Albedo_Color.svg/600px-TheTransneptunians_Size_Albedo_Color.svg.png Still More Trans-Neptunian Objects

20. The Outer Solar System KBO’s Scattered Disc Objects http://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Outersolarsystem_objectpositions_labels_comp.png/ 611px-Outersolarsystem_objectpositions_labels_comp.png

21. 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 • Possible 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° • Dynamicallyhotpopulation • Orbital eccentricity > 0.1 • Orbital inclination > 10° & < 30°

22. Eris Dysnomia http://upload.wikimedia.org/wikipedia/commons/5/5b/Eris_and_dysnomia2.jpg Eris • Basic facts • Largest known KBO • ~ 1,300 + 200 km in diameter Highly uncertain • Ninth largest known object in orbit around the Sun • One moon named Dysnomia

23. http://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Eris_Orbit.svg/644px-Eris_Orbit.svg.pnghttp://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Eris_Orbit.svg/644px-Eris_Orbit.svg.png The Orbit of Eris

24. The Öpik-Oort Cloud • Hypothesized 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 dormant long-period comets • ~ 50 to 50,000 AU from the Sun • ~ 1 light year • ~ 25% the distance to Alpha Centauri, the nearest star

25. 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 4 candidates have been identified • 2000 CR105 • 2003 Sedna • 2006 SQ372 • 2008 KV42

26. http://upload.wikimedia.org/wikipedia/commons/0/03/Kuiper_oort.jpghttp://upload.wikimedia.org/wikipedia/commons/0/03/Kuiper_oort.jpg The Kuiper Belt & Oort Cloud

27. Sedna • Named after the Inuit goddess of the sea • Discovered in 2003 • Farthest presently known natural Solar System object • Maximum possible diameter is ~ 75% that of Pluto • Orbital parameters • 76.361 AU Perihelion • Visible only when it is closest to the Sun • 937 AU Aphelion

28. http://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/ Oort_cloud_Sedna_orbit.svg/600px-Oort_cloud_Sedna_orbit.svg.png Sedna’s Orbit & the Oort Cloud