Tim travels deep into the outback of Western Australia to observe the Milky Way through clear skies. After looking up at the stars with British astronomer Dr Natasha Hurley-Walker, Tim discovers what makes the planets so different from one another.

Tim unravels the mystery of what stars are made of, how long they live and what happens when they die. He witnesses a total solar eclipse, discovers how enormous the sun is, and learns how black holes are formed.

Tim recalls the daunting moment of his first space walk, and explores life on the space station, coping with weightlessness, space food and going to the loo. And to see challenges of living on Mars, Tim visits Biosphere 2 in Arizona.