Is it a planet? Is it a black hole? Is it even real? This month, Izzie and Dr Becky try and get to the bottom of the mysterious planet nine - an enigmatic - and so far invisible - ninth planet in our solar system. Helping them are the scientists that have made headlines trying to solve this puzzle, Mike Brown from the California Institute of Technology, and Jakub Scholtz from the University of Turin. Plus, Robert Massey joins in to take on your questions and explains how to see the upcoming eclipse.

The Supermassive podcast reached 100k listens this month - thank you to everyone who has listened so far. If you’re interested in sponsoring the series (or an episode or two) then please email podcast@ras.ac.uk with the subject “sponsorship”.

This is a Boffin Media production by Izzie Clarke and Richard Hollingham