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Fifth moon discovery reminds us how little we know about Pluto (+video)

Orbiting at outskirts of the solar system some three billion miles from Earth, Pluto remains shrouded in mystery. 

By Natalie WolchoverLife's Little Mysteries / July 16, 2012

This image, taken by NASA's Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5, as photographed by Hubble's Wide Field Camera 3 on July 7, 2012.

NASA, ESA, and M. Showalter (SETI Institute)


A fifth moon orbiting the dwarf planet Pluto has turned up in new Hubble Space Telescope images.  Planetary scientists say the newfound moon serves as yet another reminder of how little we really know about this remote, chaotic world.

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Scientists in the US have announced on Wednesday the discovery of the smallest moon yet around the icy orb if Pluto, bringing the count of its known moons to five.
"We're not finished searching yet," said Hal Weaver of Johns Hopkins University, who thinks there may be more.

"Every time we look harder, we find new stuff," said Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colo., and a member of the moon's discovery team. In recent decades, he and his colleagues have identified signs of an atmosphere on the dwarf planet, as well as polar caps, a high albedo (highly reflective surface), and of course, a growing collection of moons.

But in-depth investigation of Pluto has proven tremendously difficult from 3 billion miles away. The best images we have of the icy world come from the Hubble Telescope, but to the untrained eye, they're not much to behold. At a slim 1,429 miles wide — roughly the distance from Maine to the tip of Florida — Pluto will likely remain a dim blur until NASA's New Horizons spacecraft arrives there in July 2015.

What secrets might lie in wait? [The Greatest Mysteries of the Planets]

For one thing, the dwarf planet could possess a set of everyone's favorite cosmic accessories. "It's a very distinct possibility and the theoretical arguments are very strong that Pluto has rings that come and go with time," Stern told Life's Little Mysteries.

Space rocks and other debris litter the Kuiper belt, where Pluto resides, and they probably pepper the icy world and its moons. "The moons are being hit all the time, and the ejecta [collision debris] escapes, making a ring," Stern said. "And then radiation and gravity depletes the ring through erosion."

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