A group of over 300 scientists and astronomers have started a petition (now closed) to protest the definition of a planet approved by the International Astronomers Union at a meeting last week in Prague. The new definition had the effect of demoting Pluto to "dwarf planet" status. That vote involved only 424 people who stayed for the last day of the meeting, out of around 4,000 attendees.
Sufficient signatures from planetary scientists and astronomers have been gathered to bring into serious question the definition for planet adopted by the IAU as fundamentally flawed, as was the process by which it was generated.
Signatories to the petition include prominent experts in the field of planet formation and evolution, planetary atmospheres, planetary surfaces and interiors, and international prize winning researchers.
Planning is underway to establish an open and inclusive grass-roots process by which planetary scientists and astronomers from around the world can approach a better resolution to the issue of planets in our own solar system and elsewhere, with every step and discussion in public view. This process should culminate in a conference, not to determine a winner, but to acknowledge a consensus.According to Science Daily, the debate about what is and isn't a planet is nothing new:
Astronomers discovered the asteroid Ceres on January 1, 1801--literally at the turn of the 19th century. Having no reason to suspect that a new class of celestial object had been found, scientists designated it the eighth planet (Uranus having been discovered some 20 years earlier).
Soon several other asteroids were discovered, and these, too, were summarily designated as newly found planets. But when astronomers continued finding numerous other asteroids in the region (there are thought to be hundreds of thousands), the astronomical community in the early 1850s demoted Ceres and the others and coined the new term "asteroid."
The petition sponsors plan to make an announcement later this month about how the new debate will be structured. Hopefully, in addition to Pluto they'll also give us back Planet Xena (and its satellite, Gabrielle).