1 The word astronaut, formed from two Greek words, means 'star sailor'.
2 Only flights reaching an altitude of 100 km or more are considered space flights.
3 People chosen to become NASA astronauts have to complete a difficult training program lasting 20 months.
4 Astronauts spending long periods in space do exercises designed to keep them strong.
5 Spacecraft intending to escape from Earth's gravity need to reach a speed of about 40,000 km/h.
6 People watching the Apollo 13 mission on TV or listening on the radio were very relieved when the astronauts returned safely.
7 James Lovell received the Exceptional Service Medal, awarded by NASA.
8 The film Apollo 13, made in 1995 and starring Tom Hanks, was nominated for many awards, including nine Oscars.