Pluto isn't alone—it's part of the Kuiper Belt with possibly hundreds of other planet-sized objects. Because Pluto hasn't ...

There may be an undiscovered planet in the outer solar system whose presence is revealed by the strange orbit of objects beyond the eighth planet Neptune. The tantalizing prospect of a ninth ...

The Planet Nine theory was based on several trans-Neptunian objects, those that are beyond the eighth planet, with highly “tilted” orbits compared to the ecliptic plane. This seemed odd and ...

Mercury, the closest planet to the Sun (and all the other planets), will not make the show in its current position behind the Sun, while you won't see the eighth planet because you're standing on it.

Help the Blue Peter space crew overcome the perils of space to make it to the eighth planet, and maybe learn some new facts on the way! BBC Homepage Skip to content ...