This month’s tenth planet found in Kuiper Belt – anyone following the links on the right of the BBC’s story will find many remarkably similar stories in the archives, though my favourite extra planet story is still this one (itself the runner up for best ever BBC space story, second to this and its terrific pub-quiz-busting punchline). Meanwhile, what of Sedna? It has to stand a chance of acceptance – it’s got better planet PR than Quaoar, which stumbled at the first cosmic hurdle by, well, being called Quaoar. Reading these articles I get the feeling most of the astronomers concerned would be quite happy with none of these blobs of rock being called ‘new planets’, but that Pluto has muddied definitions too much. I imagine the words “Bloody Pluto!” ring out when one of these stargazing bods picks up the paper and sees this kind of story (unless it’s their new planet of course, that’s a different matter).

If Pluto was downgraded to not-planet itself it would be a big shock: like many a curious child the names of the planets were one of the first things I ever learned. It’s actually odd to think that there are people still alive who will have clear memories of an extra planet being glommed on to our Solar System in the first place – what did they think? did they care? how long did it take for Pluto to become just part of the rote fact-baggage people carry around.

It’s an interesting question in general I reckon – facts you grew up with that have been proved wrong. I can’t think of any offhand, that may just be because it’s 9 in the morning though.