The brightness variations could be due to craters and basins, methane and nitrogen frosts, or even areas of primordial organic matter. No one knows, and the mystery may remain until some future spacecraft pays a visit to this distant planet. That's what astronomers have been discussing since late last year when some members of the International Astronomical Union suggested that Pluto be given a minor planet designation. For one thing Pluto is very small. Pluto's own moon, Charon, is larger in proportion to its planet than any other satellite in the solar system.
Some astronomers consider the pair to be a double planet.
Astronomers once thought that Pluto may have been a satellite of Neptune's that was ejected to follow a tilted elliptical path around the sun. However, careful simulations of the orbits and dynamics of Pluto and Neptune indicate that this is an unlikely scenario. Once again, Pluto is a misfit. Pluto behind the 8 ball Despite its well-known peculiarities, Pluto's official status as a planet was never in jeopardy until 1992 when David Jewitt and J. Luu discovered a curious object called 1992 QB1. QB1 is a small icy body, similar in size to an asteroid, orbiting 1.5 times further from the sun than Neptune.