Pluto & Friends - Outline

[Pages:43]Pluto & Friends - Outline

? Discovery of Pluto ? Characteristics of Pluto ? Characteristics of Charon ? Pluto's Downfall as a Major Planet ? Large Kuiper Objects ? The IAU Resolution

Discovery of Pluto

? Another planet required to account for apparent perturbations in the orbits of Uranus & Neptune

? Unsuccessful attempts were made by Percival Lowell to find an additional planet

? Finally discovered in 1930 by Clyde Tombaugh using a newly developed wide-field camera at the Lowell Observatory

? Pluto was named after the Roman god of the underworld, and Charon (Pluto's moon) was named after the mythical boatman who carried the dead into the realm of Pluto

Discovery Photographs (Note - new techniques & instrumentation drive a lot of ground-breaking science)

Clyde Tombaugh. 65% of the sky photographed & thousands of hours logged over a 10-month period leading up to the discovery of Pluto

Properties of Pluto

Atmosphere: Nitrogen & other gases that sublimate from the surface

? Average Distance from the Sun: 5.5 light hours (39.5 AU)

? Rotation Rate: 6.4 Earth days

? Orbital Period: 248 Earth years

? Axis Tilt: 118?

? Number of Moons: 3

Pluto's Orbit

? Orbital Inclination = 17?

? Orbital Eccentricity = 0.25 For a circular orbit, Eccentricity = 0.0 Mercury's Eccentricity = 0.21 Aphelion = 49.3 AU; Perihelion = 29.3 AU Effect ! sublimation & refreshing of volatiles on the surface of Pluto

? Axis Tilt = 118? Axis Tilt of Uranus = 98?

Pluto's orbit Relative to the Other Planets

Map of the Surface of Pluto

? Mass = 0.25% Earth's Mass ? Density = 2.1 g cm-3 ? Surface: Reflectivity ~ 30-50%

Methane Ice ! Bright Spots ?? ! Dark Spots

Charon - 1978 discovery

? Mass = 10% Pluto's Mass (Mmoon = 1.25% Mearth) ? Density = 1.6 g cm-3 (a bit low) ? Surface = water ice ? Charon's orbital period is equal to Pluto's rotation period ? Formation? Similar to the formation of the Moon, which

explains densities

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