As British astronaut Tim Peake exits the safety of the International Space Station for his very first spacewalk, Brian Cox and Dara O Briain watch him every step of the way in this Stargazing Special. They are joined by someone with a unique insider's view and who has done this himself, astronaut and former Space Station commander Chris Hadfield. Find out about the perils that Tim is facing and what is really going on as he carries out time-critical emergency repairs in the dangerous vacuum of space.

• Dara Ó Briain
• Brian Cox
• Liz Bonnin