Nature is reporting that Owen Gingerich, head of the International Astronomical Union (IAU) consulted the Microsoft Word and the WordPerfect spellcheckers to help gauge how common the term pluton is.  Pluton, of course, is the new term proposed by the IAU for celestial bodies which aren't quite planets.  But it was also already a technical term used by geologists for a kind of igneous rock formation.  Here's what the Nature article said:

"Since the term is not in the MS Word or the WordPerfect spell checkers, we thought it was not that common," Gingerich wrote in an e-mail to news@nature.com. The geologic definition of the word does appear in common dictionaries, including the Oxford English.

"Pluton" is indeed not included in the last version of the Office spellchecker.  Nor is it due to be in the next version, at this point (but that could change if the newly proposed usage makes the term a lot more common).  Why not?  Essentially because a spellchecker is not meant to be an exhaustive list of all the correctly-spelled words in a given language.  A spellchecker is primarily a tool to help people spell better.  We've already mentioned one reason why we might deliberately exclude certain words from the spellchecker: sometimes a word is rare enough that when a user types it, it's more likely to be an error than not.  Of course, that can all change in a heartbeat when an international scientific body decides to start using an old word in a new way.  Will pluton catch on?  We'll be keeping our eyes peeled.

-- James Lyle (Test Lead)