5 live Science

This week Dr Chris is joined by nanoscientist Colm Durkan, astronomer Carolin Crawford, existential risk specialist Haydn Belfield and chemist Ljiljana Fruk for a romp through the latest science questions you've been sending in, including what's the Doomsday Clock, how massive is the largest star ever discovered, what's the threat from climate change, and what's a Parsec..."