Melvyn Bragg and guests discuss the Kuiper Belt, a vast region of icy objects at the fringes of our Solar System, beyond Neptune, in which we find the dwarf planet Pluto and countless objects left over from the origins of the solar system, some of which we observe as comets. It extends from where Neptune is, which is 30 times further out than the Earth is from the Sun, to about 500 times the Earth-Sun distance. It covers an immense region of space and it is the part of the Solar System that we know the least about, because it is so remote from us and has been barely detectable by Earth-based telescopes until recent decades. Its existence was predicted before it was known, and study of the Kuiper Belt, and how objects move within it, has led to a theory that there may be a 9th planet far beyond Neptune.

With

Carolin Crawford Public Astronomer at the Institute of Astronomy and Fellow of Emmanuel College, University of Cambridge

Monica Grady Professor of Planetary and Space Sciences at the Open University

And

Stephen Lowry Reader in Planetary and Space Sciences, University of Kent

Producer: Simon Tillotson.