14b. Pluto, Kuiper Belt & Oort Cloud Pluto Pluto s moons The Kuiper Belt Resonant Kuiper Belt objects Classical Kuiper Belt objects Pluto Data: Numbers Diameter: 2,290.km 0.18. Earth Mass: 1.0. 10 22 kg 0.002. Earth Density: 2.0. water 0.36. Earth Orbit: 5.9. 10 9 km 39.53 AU Day: 6 d.09 h 17 m 51 s 0.27. Earth Year: 248.6 years 248.6. Earth The Oort Cloud 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 H 2 & He poor planets with solid surfaces Satellites much smaller than parent planets Jovian planets H 2 & 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 QB 1 ~ 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 QB 1 ~ 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 memberspluto 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 Pluto In Color http://en.wikipedia.org/wiki/image:thekuiperbelt_classes-en.svg http://upload.wikimedia.org/wikipedia/en/3/30/pluto.jpg Pluto rotating The Discovery of Hydra & Nix The Largest Plutinos Pluto's moons http://upload.wikimedia.org/wikipedia/commons/3/31/pluto_system_2005_discovery_images.jpg 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) 8 Largest Trans-Neptunian Objects http://upload.wikimedia.org/wikipedia/commons/thumb/c/c0/ TheTransneptunians_73AU.svg/800px-TheTransneptunians_73AU.svg.png http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/eighttnos.png/800px-eighttnos.png
Still More Trans-Neptunian Objects The Outer Solar System KBO s Scattered Disc Objects http://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/ TheTransneptunians_Size_Albedo_Color.svg/600px-TheTransneptunians_Size_Albedo_Color.svg.png http://upload.wikimedia.org/wikipedia/commons/thumb/8/81/outersolarsystem_objectpositions_labels_comp.png/ 611px-Outersolarsystem_objectpositions_labels_comp.png 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 Dysnomia Eris http://upload.wikimedia.org/wikipedia/commons/5/5b/eris_and_dysnomia2.jpg 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 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
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 CR 105 2003 Sedna 2006 SQ 372 2008 KV 42 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