Comet of the Century: A Horizon Special

It was hoped that Comet ISON could be the brightest and most spectacular comet for a generation. After travelling towards the sun for ten thousand years, it appeared to have been disintegrated by the heat and tidal forces of the sun in early December 2013. But ISON's tail of vapourised gas and water, hundreds of millions of kilometres long, may give insights into some of the greatest mysteries of science.