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Slide 2 Confessions of a Pluto Hater Megan K. Pickett Associate Professor of Physics Lawrence University 14 November 2006 Slide 3 Friends, Students, Scientists, lend me your ears; I come to bury Pluto, not to praise it. The evil this rock does lives in our books, The small good was interred with Clyde's bones; So let it be with Pluto...The noble Newton Hath told you Pluto was Perturber: If it were so, it was a grievous fault, And grievously hath Pluto not answer'd it... Here, under leave of Lowell and the rest- (For Lowell was a crazy nearsighted man; who saw lines on Mars and shouted "water, ho!")- Come I to speak on Pluto, Dwarf Planet... Slide 4 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 5 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 6 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 7 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 8 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 9 Formerly the Ninth Planet of the Solar System uto Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 10 The Pluto Formerly Known as Planet Average Orbital Distance: 40 AU Orbital Period: 248 years Orbital Inclination:17 o Orbital Eccentricity:25% Rotation Period:-6.4days Radius:0.6 R M Mass: 0.3M M Average Density:2100 kgm -3 Surface Temperature:33 - 55 K Atmosphere: CH 4 and N 2 Surface: CH 4 ice (?) Interior (?):Silicates & ices Slide 11 History of Discovery Classical Planets: Mercury, Venus, Mars, Jupiter & Saturn Uranus: (1781) Herschel Neptune: (1864) Adams & Leverrier Ceres: (1801) Piazzi (asteroid and now Dwarf Planet) Slide 12 History of Discovery Percival Lowell Clyde Tombaugh Pluto: 1930 Slide 13 I.A.U. Circulaire No. 255 BUREAU CENTRAL ASTRONOMIQUE DE L'UNION ASTRONOMIQUE INTERNATIONALE OBSERVATOIRE DE COPENHAGUE TRANSNEPTUNIAN PLANET? Lowell observatory telegraphs systematic search begun years ago supplementing Lowells investigations for Transneptunian planet has revealed object which for seven weeks has in rate of motion and path consistently conformed to transneptunian body at approximate distance he assigned fifteenth magnitude position march twelve three hours G.M.T. was seven seconds of time west from delta geminorum agreeing with Lowells predicted longitude. Slide 14 History of Discovery Nix & Hydra: (2005) Pluto Companion Search Team Charon: (1978) Christy Slide 15 History of Discovery 1990s: Here come the Kuiper Belt Objects! 1992: 1992 QB 1 David Jewitt & Jane Luu. Currently ~1000 KBOs known. Slide 16 History of Discovery Late 1990s to Present: A TransNeptunian Zoo. Slide 17 History of Discovery And then there was Eris (& Dysnomia): Scatter Disk Object 2005 Brown, Trujillo & Rabinowitz Slide 18 A Brief History of the Solar System 1.Collapse of cold pre-stellar cloud (~5GYA) a)Initial cloud contains mass and angular momentum of Solar system b)Why does it collapse? Marginally unstable to collapse? Triggered collapse? 100 AU 0.1 pc10 5 yrs Slide 19 A Brief History of the Solar System Well, what next? Slide 20 A Brief History of the Solar System 2.The Solar Nebula (Kant 1775, Laplace 1796) a)Close to the Protosun (inside the frostline), volatiles are vaporized, and only refractory elements are available for planet building by accumulation and then accretion. ~8 AU Inner planets are rocky Slide 21 A Brief History of the Solar System 2.The Solar Nebula (Kant 1775, Laplace 1796) b)Far from the Proto-Sun, Ices are also available for Building planetary cores. ~80 AU Outer Solar System is (or should be) very different from inner Solar System. Slide 22 A Brief History of the Solar System 3.Planet Formation a)Terrestrial Planets: relatively straightforward. b)Gas & Ice Giant Planets: Phasers at Dawn. Core Accretion Takes Too Long Spiral Instability Doesnt Work vs. Slide 23 A Brief History of the Solar System 4.Planet Billiards a)Jupiter, Saturn, Uranus & Neptune migrate after formation (e.g., the Nice Model 2004) Initially J,S close; Neptune inside Uranus orbit; KBO 20-30 AU J,S migrate in and out, respectively=> fling out Neptune, KBOs Neptune clears primordial KB, captures Triton, perturbs PLUTO Slide 24 A Brief History of the Solar System 4.Planet Billiards b)Bombardment Forms Earth & Moon May form Martian satellites May form Pluto-Charon Slide 25 A Brief History of the Solar System 4.Planet Billiards c)Populate Scattered Disk, Oort Cloud. d)Delivers volatiles to inner solar system. 5.Solar Ignition a)Hydrogen Fusion (p-p chain) begins in core of Sun So where does this leave Poor Old Misbegotten Pluto? Slide 26 Pluto is Not a Planet 1.On August 24 2006, members of the IAU finally came to their collected senses and voted Pluto out of the Ritzy Planet Club. Was this mean? Logical? Or both? Whats the case against Pluto? Slide 27 Real Planets dont look like tiny plates of quiche Slide 28 a) Pluto is Bloody Tiny. Slide 29 Real Planets dont look like tiny plates of quiche b) Plutos orbit is unlike any of the other planets. Slide 30 Real Planets dont look like tiny plates of quiche c) There are a lot of tiny icy bodies out there, too. Slide 31 Real Planets dont look like tiny plates of quiche d) Pluto is a binary object What to do about Pluto, then? Slide 32 Fortunately, we already have an object parked in Saturn Orbit that seems right for the job. Slide 33 Real Planets dont look like tiny plates of quiche 2.Thus Sayeth the IAU: A Planet is an object that 1. orbits the Sun (so far so good); 2. is massive enough to pull itself into a sphere (again, good enough); and 3. has cleared the region of objects, i.e., is in some sense locally gravitationally independent. And so, mercifully, Pluto, along with Eris and Ceres and probably many, many more are Dwarf Planets. DOh! Slide 34 Now cracks an icy sheath. Good night, odd ball, And flights of comets sing thee to Kuiper!"