Dara and Brian's journey through the night sky continues with a look at black holes, the most mysterious and destructive objects in the whole universe. Liz Bonnin finds out how our galaxy the Milky Way was formed and Mark Thompson investigates the problems that are caused by light pollution.

On the final night of their astronomical adventure, Prof Brian Cox and Dara O Briain discuss aliens, extra terrestrial life and the hunt for new worlds far outside our solar system. They also find out if they've been successful in their quest to find their own Stargazing planet.