The revisionists are at it again, trying to demote Pluto as the solar system's ninth planet. It is nothing more than a giant ice cube, according to the American Museum of Natural History in New York.
The Museum's Rose Centre for Earth and Space has a huge display featuring all the planets including a 2.7 m diameter model of Jupiter. The only problem is that it details eight planets, not nine. Pluto becomes a footnote and is described as one of a number of small icy worlds. This isn't the first time that someone decided to have a go at poor Pluto. The august International Astronomical Union allowed debate during 1999 on a proposal to de-list the planet, but such was the outcry from astronomers the suggestion was rejected.
The object that is causing such upset is a pretty unimposing component of the solar system. Discovered in 1930, it measures only 2,274 km wide, smaller than our moon. It is also an oddball of a planet. All other planets orbit the sun in a circular pattern along a single flat plane but Pluto has an elliptical orbit, tilted 17 degrees out of line with everyone else.
Still, everyone was excited when it was found and were willing to stick with it until 1992 when researchers discovered a curious object called QB1, a small icy body well out beyond Neptune. Since then almost 100 similar objects have been found and all are thought to be similar in composition and density to Pluto.
There is an entire swarm of Pluto-like objects out there past Neptune in a region known as the Kuiper Belt thought to be alive with the detritus left over after the planets were formed. It is thought to be a source of those comets which visit us over short periods.
Comets and the Kuiper Belt objects are made of rocks and ice. What does Pluto seem to be made of? Rocks and ice. So is Pluto a planet or a dormant comet? For the moment, the IAU will keep Pluto's status safe. But watch this space. If a Kuiper Belt object larger than Pluto is found the knives will be out again, the diminutive planet might suddenly be reclassified and schoolbooks will have to be scrapped for newer versions.
