Pluto took a big hit in the eyes of schoolchildren and amateur astronomers two years ago when the International Astronomical Union (IAU) knocked it out of the rank of planets. Deemed too small and irregularly shaped, and with its orbit in the path of another planet, Pluto was relegated to a new class of "dwarf planets." The reclassification came about as the result of discoveries of bodies beyond Pluto's orbit that are the same size or larger than the icy world. And so Pluto was grouped with those far-out solar-system denizens, along with asteroids close to Pluto's size.

The most exclusive club in the solar system will be revising its membership rules this year

In all of history, only nine orbs in the sun's entourage have earned the title "planet." But that changed last summer, when an object significantly bigger than Pluto was spotted lurking in a little-explored region of the solar system known as the Kuiper Belt.