faces of pluto

Long thought to be the 9th planet, then reclassified in 2006 as a dwarf planet, Pluto is now also honored as the first plutoid. It has an atmosphere and five known moons: Charon, Styx, Nix, Kerberos, and Hydra. Since it passed perihelion in 1989, it has been receding from the sun and it was interesting that the atmosphere was still warming when we started observing it in 2002. We are now participating in monitoring the atmosphere’s temperature and density, with a view toward understanding conditions there when NASA’s New Horizons spacecraft arrives there in 2015.

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