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. (Photo : NASA)
It may have been kicked out of our solar system rather unceremoniously for being too small, but Pluto is still big enough to have several moons orbiting it. Now, astronomers have discovered another moon orbiting the icy dwarf planet, bringing the total number of moons around Pluto to five.
The discovery was prompted by NASA scientists scanning the skies with the Hubble Space Telescope to try and figure out any potential hazards to the New Horizons spacecraft.
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The new moon, named S/2012 (134340) 1, is irregular in shape and around 6 to 15 miles across. It has 58,000 mile orbit around the dwarf planet.
"The moons form a series of neatly nested orbits, a bit like Russian dolls," said team lead Mark Showalter of the SETI Institute.
The team is amazed at how a dwarf planet such as Pluto can have such a complex system of satellites and orbital patterns. Earth, by contrast, only has one moon, and Jupiter, our solar system's largest planet, has over 60.
Pluto's fourth moon was discovered in 2011, and has astronomers wondering about the complexity of debris at the edge of our solar system.
"The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system," said Harold Weaver of the Johns Hopkins University Applied Physics Laboratory.
The identification of these small objects will be important for NASA's New Horizons mission, which, in 2006, launched the New Horizons spacecraft to Pluto and beyond. The New Horizons spacecraft has currently passed Uranus, meaning it is technically out of our solar system, and is on its way to Pluto. The spacecraft is slated to pass Pluto in July 2015, after nearly 10 years of traveling through space.
The spacecraft will need an accurate map of debris to avoid on its long journey where it is covering around 15 km/s at the moment.
"The inventory of the Pluto system we're taking now with Hubble will help the New Horizons team design a safer trajectory for the spacecraft," added Alan Stern of the Southwest Research Institute, the mission's principal investigator.
Pluto was reclassified as a dwarf planet in 2006, bringing the number of planets in our solar system down to eight. This was due to the International Astronomical Union finally defining what a planet exactly is, and the new classifications made Pluto a dwarf planet.