Hi, it's Dan from the Week Junior Science and Nature magazine here.

We've got so many excellent episodes in our archive of Mysteries of Science

that we're revisiting one of our old episodes.

In this episode, we go in search of a mysterious planet X.

Hello and welcome to an intergalactic episode of Mysteries of Science.

My name's Dan and I'm the editor of Science and Nature, the monthly magazine from the team behind the week junior.

And I'm Kieran, the features editor.

In each issue of science and nature, we explore the universe through in-depth features, news stories, images, interviews with top experts and much

more. And in each episode of this very podcast, we investigate a weird or unexplainable area

of science or the natural world. We've looked into so many great mysteries in this first

series of podcasts. But one of my favourites has to be the aliens episode

and our investigation into extraterrestrials.

Tell you what, Kieran, how do you fancy taking another journey into space?

Well, I'll never say no to a journey into space.

Are there any other mysteries for us to solve, though?

I thought sort of aliens was the only big question mark about the universe we had left.

Aha, good question.

Well, you might think that, but I've got a planet-sized mystery for us to investigate today.

And even the brightest brains at the world's top space agencies haven't found a solution to it yet.

A planet X is this mysterious planet, okay?

So X stands for unknown, and it's thought to exist in the far-flung, darkest depths of our solar system.

Some people say there's evidence that Planet X must be out there, but nobody's actually ever found the planet itself.

...