A proposal by the astronomer Brian Marsden that the planet be renamed "Trans-Neptunian Object No 10,000" has caused such a stellar row between astronomers worldwide that the IAU was forced to issue a statement, to quell "widespread public concern".
Not since astronomers struggled with the preferred pronunciation of Uranus has the discipline been so divided.
Dr Marsden, the head of the Minor Planet Center in Cambridge, Massachusetts, has already identified 9,999 "trans-Neptunian objects". Now he believes that Pluto should become No 10,000 and he may have science on his side.
Pluto is quite unlike the other eight planets. Discovered in 1930, almost a century after Neptune, it is a minuscule, rocky body unlike the other outer planets, which are huge, gaseous giants.
It has a highly elliptical orbit, which means that until later this year it lies inside Neptune's orbit - making it a trans-Neptunian object (TNO).
Furthermore, it orbits at an angle of 17 degrees compared with all the other planets.
But the idea is not proving popular. "There is ... denigration of the idea that such things as Pluto could be put in the same category as asteroids," Dr Marsden said.
"Somebody said to me, `Why classify Pluto with the cosmic riff-raff?' It's unfortunate but some people are being extremely dogmatic."
Earlier this week the American Astronomical Society, one of the most powerful in the world, made the bald statement that "this action would undoubtedly be viewed by the broader scientific community and the general public as a `reclassification' of Pluto from a major planet to a minor planet. We feel that there is little scientific or historical justification for such an action."
Donald Yeomans of the AAS said from his office at Nasa's Jet Propulsion Laboratory: "We're hoping for a statement from the IAU soon, and we have recommended that the status quo be maintained. We have had correspondence from hundreds of astronomers and there's very little support for doing anything to Pluto."
An alternative to Mr Marsden's radical idea, being considered by the IAU, would be to define Pluto as both a major and a minor planet.
Either way, the IAU's Executive Committee (Division III) will soon vote on the matter - though Dr Michael A'Hearn, its chair, insists that any decision "will not alter either the true nature of Pluto or the historical record of its having been generally considered a planet".Reuse content