Pluto and its moons are far more complicated than scientists bargained for when New Horizons left Earth on Jan 19, 2006.

For one thing, Pluto was officially reclassified from being a planet in the solar system to the category of dwarf planet.

In August 2006, just months after New Horizons launched, scientists at the International Astronomical Union's general assembly voted to "demote" Pluto from its status as a "major planet" to that of "dwarf planet." The controversial vote was met with disdain by the public and planetary scientists alike.

But New Horizons Principal Investigator Alan Stern never stopped believing in Pluto's status as a planet, even if it is little.



"A planet is an object in space that is large enough to be called big, therefore a planet. What is the definition of big? Rounded by gravity," Stern said.

"Anything that's big enough to be round, we call a planet, as long as it's not a star."