For centuries, scientists have searched for the mythical and elusive Planet X, out beyond Neptune. And until now, it has remained just that - a myth. Well, now a pair of American astronomers say that although they haven't actually seen the planet directly, they have the evidence to show its influence on other bodies in the distant Kuiper Belt. And they think the Neptune-sized planet - which they've dubbed Planet 9 - could change our view of the Solar System. Ironically, one of those astronomers is the man who helped to kill Pluto's status as a planet.

Plus - Over-fishing goes deeper than we thought; and hundred of species of bugs are freeloading in your home

Click here for the full episode; individual segments; streaming audio; MP3 downloads, and more