The 53-year-old Hadfield launched aboard the Russian Soyuz spacecraft in December and in March became the first Canadian to lead a spaceship as commander of the International Space Station.

CNN: Astronaut sings Bowie's 'Space Oddity' in zero gravity

Two million: The number of air miles clocked up by British businessman Alan Watts to win the chance to become the first "air miles astronaut" aboard a Virgin Galactic spaceship in 2009.

CNN: The day in numbers: Two million