Discovery of Pluto by Clyde Tombaugh on February 18, 1930. The object moved, the background stars did not. Lick Observatory images are 1 day

apart

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Pluto (diameter ~ 2320 km; surface T = - 390° F) and its moon Charon imaged by the Hubble Space Telescope

Charon was discovered in 1978 and is ~ 1,200 km in diameter

Pat Rawlings conception of the Pluto-Charon binary-planet system (left-front = Charon; right-back = Pluto)

Relative sizes of Pluto, Charon, and the US. Pluto is 2,320 km and Charon ~ 1,200 km in diameter

Pluto’s unusual orbitIt is steeply inclined (17°) and highly eccentric (0.25). At times, Pluto’s orbit

reaches inside that of Neptune

The New Horizons Mission – the race to catch the atmosphere of Pluto before it freezes in ~2015

Launch January 19, 2006

(Jupiter fly-by February 2007)

Pluto encounter in July 2015