It appears as though Pluto may be on the virge of becoming a planet once again.
“...The IAU had originally proposed something similar, but in Prague one faction objected. They pointed out that Pluto is really just a piece of debris, merely one of a swarm of icy objects out beyond Neptune called the Kuiper belt. The objectors complained that under the simple definition, many Kuiper belt objects would achieve planet status and they persuaded the meeting to add the condition that a planet must have either thrown out or sucked up any nearby junk, or in their words, “cleared the neighbourhood around its orbit”. Only the eight planets from Mercury to Neptune meet that condition.
It is also the sticking point. “It is a horrible mistake,” says Alan Stern of the Southwest Research Institute in Boulder, Colorado, who leads NASA’s New Horizons mission to Pluto. “Any definition that allows a planet in one location but not another is unworkable. Take Earth. Move it to Pluto’s orbit, and it will be instantly disqualified as a planet.”…”