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initial attempts to produce orbit for Uranus unsuccessful

NEPTUNE. initial attempts to produce orbit for Uranus unsuccessful 1821: Bouvard produces orbit based on contemporary observations includes gravitational influences of Jupiter and Saturn. deviations between prediction and observations ( perturbations ) increase with time.

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initial attempts to produce orbit for Uranus unsuccessful

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  1. NEPTUNE • initial attempts to produce orbit for Uranus unsuccessful • 1821: Bouvard produces orbit based on contemporary observations • includes gravitational influences of Jupiter and Saturn • deviations between prediction and observations (perturbations) increase with time • discrepancy possibly due to gravitational perturbations of an unknown planet Problem: use the observed perturbations to predict location of the unknown

  2. Adams (English) • approximate method to determine location and mass (1843) • used Newton's laws of Mechanics and Gravitation • assumed circular orbit, twice the radius of Uranus' • dropped assumptions when more accurate data obtained • calculated orbit and mass of the unknown (1845) • orbit presented to Challis and Airy at Cambridge Observatory • search delayed due to concerns of Challis and Airy LeVerrier (French) • determined size of perturbations very precisely by examining effects of Jupiter and Saturn • assumed orbit fit T-B law (38.8 AU) • also used Newton's Laws • produced ephemeris (August, 1846)

  3. The Race • Adams becomes aware of Leverrier's work , requests Challis begin search for object • Challis begins observing (July 1846) • Cambridge lacked detailed sky maps of region • necessitates large amount of data analysis, Challis reluctant • Leverrier's ephemeris sent to Galle at Berlin Observatory (Sept. 23, 1846) • uses new Star Map of the Berlin Academy (created in response to discovery of asteroids) • locates a new object within 52' of prediction • Galle and Enke confirm object moves • must be planet - Neptune

  4. The Aftermath • British had observed Neptune on Aug. 4 and 12 • didn't analyse the observations until after discovery at Berlin • controversy over credit • Galileo may have observed it in 1612-13 • Neptune's orbit has radius of 30.1 AU, period 164 years • T-B law discredited • discovery added credence to Newton's theories Mercury • LeVerrier examines Mercury's orbit • perihelion advance (1.5° per century) • gravitational perturbations account for all but 40" of the advance • suggested existence of another planet (Vulcan)- never found

  5. PLUTO • Uranus' orbit apparently still had unaccounted perturbations • Lowell predicts position of another unknown object • Clyde Tombaugh searches for planet at Lowell Observatory • uses blink comparator • Feb. 1930: discovers object within 6° of Lowell's prediction – Pluto Pluto and Charon • orbit: 39.5 AU, period 248 years • perturbations of Uranus were not produced by Pluto

  6. MOONS AND MINOR BODIES • many new moons discovered as telescope resolution improves • 1877 - 2 moons of Mars Deimos Phobos • 1978 - Pluto's moon Charon • 2005 - 2 more moons for Pluto (discovered with HST) • Jupiter - 63, Saturn - 34

  7. Oort Cloud (1950) • collection of rocky/icy bodies out to 50,000 AU • home of long-period comets • Kuiper Belt (1951) • rocky objects beyond Pluto, out to 500 AU • home of short-period comets • Quaoar, Sedna - similar to Pluto • Eris (2006) - larger than Pluto Sedna Quaoar’s orbit

  8. Dwarf Planets (August 2006) • round due to gravity • not heavy enough to clean majority of nearby space • Pluto, Ceres Trans-Neptunian Objects

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