The Hubble Space Telescope (HST) has discovered a fifth moon orbiting Pluto!

Using the HST’s Wide Field Camera 3, astronomers discovered the diminutive moon during a series of observations in late June and early July.  The moon, currently called P5, is irregular in shape and has a diameter between 6 and 15 miles.  It orbits Pluto from an average distance of 29,000 miles.

Pluto was discovered on February 18, 1930, by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona.  Pluto has a diameter smaller than our own moon.  It orbits the Sun from an average distance of about four billion miles.  However, its highly eccentric orbit takes Pluto as close as three billion miles and as far as five billion miles.  It crosses the orbit of Neptune for twenty of its 248 year orbit.  The orbital dynamics are such that the two worlds will never collide.  The average temperature on Pluto is almost -400F.  It is composed primarily of rock and ice and has an extremely thin nitrogen atmosphere.

Pluto has five known moons- Charon, Nix, Hydra, P4, and P5.  Charon, the largest of Pluto’s moons, was discovered in 1978.  Nix and Hydra were discovered in 2005 by astronomers using the Hubble Space Telescope.  P4 was spotted in 2011.

In 2006, Pluto was reclassified from Planet to Dwarf Planet.  Before its change of title, Pluto was the only planet in the solar system not to be visited by a spacecraft.  The New Horizons spacecraft was launched and will fly past Pluto in July, 2015.  Its primary goal is to learn more about Pluto and the other icy objects, known as Kuiper Belt Objects, which reside in the farthest reaches of our solar system.

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