If you are unhappy about Pluto losing its official status as a planet, the good news is that there may be a 9th one that we’ve missed so far, orbiting out beyond Pluto with a period of 10,000–20,000 years. While not yet seen directly, Konstantin Batygin and Michael E Brown of Caltech argue that just such a planet, with a mass of around 10 Earth masses or more, explains an otherwise mysterious clustering seen in Kuiper-belt objects. It spends much of the time very far from the Sun, so would be hard to see directly, but the Subaru Telescope in Hawaii has a chance, as does the Large Synoptic Survey Telescope in Chile, which should start operating within 10 years.