Two years after it was excluded from the planet class of celestial objects, Pluto has been vindicated and its name was lent to similar objects formerly known as dwarf planets. The new classification says that such objects, plutoids, are ones which satisfy all three of a set of conditions.

The first requirement is that the celestial object is orbiting the Sun at an average distance greater than that of Neptune. Furthermore, it has to be massive enough that its own gravity brings it to hydrostatic equilibrium, making it near-spherical, and, finally, it has not cleared the neighborhood around its path from other orbiting debris.

Planets are usually characterized by the fact that they managed to clear their vicinity of space debris. This distinguishes them from plutoids, which are too small to have done so. Only one other plutoid has been found so far. It is Eris, the giant Kuiper belt object (KBO), but other objects are being investigated to see if they belong to this category. They are giant KBO's 2005FY9, known informally as "Easterbunny," and 2003EL61, nicknamed "Santa."

The problem was that when Eris was discovered, it created controversy over its similarity with Pluto. The issue was that either Eris was to be acknowledged as the 10th planet in our solar systmem, or Pluto should have been kicked out, effectively limiting the number of planets to eight. The latter solution was adopted in 2006, which howewer did not entirely solve the problem.

The latest decision by the members of the International Astronomical Union (IAU) has thus created a new celestial object class, that of plutoids, in which both Pluto and Eris were included.