Tuesday, August 23, 2011

Pluto - Downgraded and Downsized

It was 5 years ago that the International Astronomical Union downgraded Pluto to a newly created category of dwarf plant. This new category helped explain the ring of icy bodies beyond Neptune that make up the Kuiper Belt. Pluto dilemma was created by the discovery in 2005 of a second major Kuiper object, Eris. Eris was rightly named for the Goddess of discord and strife. She is credited with stirring up enough jealously and envy to cause the Trojan War and now centuries’ later discord among astronomers. When discovered by American Clyde Tombaugh in 1930, Pluto was thought to be larger than Mercury and possibly bigger than the Earth. Since then it has been downsized to about 1,455 miles across which is less than 20% as large as Earth. Plus it is 0.2% of Earth’s mass. It’s extremely elliptical orbit is not on the same plane as the eight official planets and at times makes it overlap Neptune orbit. During this time it is closer to the sun than the gas giant. It takes 248 Earth years to complete one circuit around the sun at an average distance of 3.65 billion miles. This distance makes Pluto one of the coldest places in the solar system with surface temperatures hovering around -375ºF. It has 4 known moons, Charon, Nix, Hydra and a newly discovered tiny one presently called P4. Charon is about half the size of Pluto which leads some astronomers to regard Pluto and Charon as a double dwarf planet or binary system. Even though it is smaller than Earth’s moon, Pluto has managed to hold onto a thin atmosphere composed mainly of nitrogen, methane and carbon monoxide that extends about 1,860 miles into space and changes color. Just recently it discovered by NASA’s New Horizon spacecraft that Charon also has an atmosphere. New Horizon should reach Pluto in July 2015 giving us a new outlook on the tiny worlds at the edge of our solar system. Info credit to Space.com Photo credit Space photos comparing USA/Pluto/Charon

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