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14b. Pluto, Kuiper Belt & Oort Cloud. Pluto Basic characteristics Pluto’s moons The Kuiper Belt Basic characteristics Resonant Kuiper Belt objects Classical Kuiper Belt objects The Oort Cloud Basic characteristics. Pluto Data: Numbers. Diameter:2,290.km0.18 . Earth - PowerPoint PPT Presentation
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14b. Pluto, Kuiper Belt & Oort Cloud• Pluto
– Basic characteristics– Pluto’s moons
• The Kuiper Belt– Basic characteristics– Resonant Kuiper Belt objects– Classical Kuiper Belt objects
• The Oort Cloud– Basic characteristics
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
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
Pluto Data (Table 14-5)
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 13 March 1930
• 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
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
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
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
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 ? ? ?
Computer-Derived Views of Pluto
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 ! ! !
Resonant Kuiper Belt Objects• 1:2 resonance Twotinos
– 14 confirmed members• 2:3 resonance Plutinos
– 92 confirmed members
Pluto is the naming member– 104 possible members
• 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
Resonant TNO Orbits
http://en.wikipedia.org/wiki/Image:TheKuiperBelt_classes-en.svg
Pluto In Color
http://upload.wikimedia.org/wikipedia/en/3/30/Pluto.jpg Pluto rotating
The Discovery of Hydra & Nix
http://upload.wikimedia.org/wikipedia/commons/3/31/Pluto_system_2005_discovery_images.jpg
Pluto's moons
The Largest Plutinos
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/ThePlutinos_Size_Albedo_Color2.svg/250px-ThePlutinos_Size_Albedo_Color2.svg.png
Trans-Neptunian Objects (TNO’s)
http://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/TheTransneptunians_73AU.svg/800px-TheTransneptunians_73AU.svg.png
8 Largest Trans-Neptunian Objects
http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/EightTNOs.png/800px-EightTNOs.png
Still More Trans-Neptunian Objects
http://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/TheTransneptunians_Size_Albedo_Color.svg/600px-TheTransneptunians_Size_Albedo_Color.svg.png
The Outer Solar System
http://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Outersolarsystem_objectpositions_labels_comp.png/611px-Outersolarsystem_objectpositions_labels_comp.png
KBO’s ScatteredDisc
Objects
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°
– Dynamically hot population• Orbital eccentricity > 0.1• Orbital inclination > 10° & < 30°
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
http://upload.wikimedia.org/wikipedia/commons/5/5b/Eris_and_dysnomia2.jpg
Dysnomia
Eris
The Orbit of Eris
http://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Eris_Orbit.svg/644px-Eris_Orbit.svg.png
The Öpik-Oort Cloud• Hypothesized by two astronomers
– Ernst Öpik Estonian1932
• 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
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 objectsOCO’s
– Only 4 candidates have been identified• 2000 CR105• 2003 Sedna• 2006 SQ372• 2008 KV42
The Kuiper Belt & Oort Cloud
http://upload.wikimedia.org/wikipedia/commons/0/03/Kuiper_oort.jpg
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
Sedna’s Orbit & the Oort Cloud
http://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Oort_cloud_Sedna_orbit.svg/600px-Oort_cloud_Sedna_orbit.svg.png