For more than 70 years Pluto was counted as the ninth planet, an isolated but sentimental favourite at the end of the solar system. But in recent years this little world has been at the centre of a neighbourhood dispute of cosmic proportions. Just what on Earth caused Pluto to be struck off as a planet? It now seems Pluto has company, and lots of it. And we have more in common with this distant realm than you may have ever imagined.