26. Twice during Mercury’s orbit, it gets so close to the Sun and speeds so much that the Sun seems to go backwards in the sky.
27. Nicolaus Copernicus was the astronomer who first suggested that the Sun was the centre, and that the Earth went round the sun.
28. The ideas of Copernicus came not from looking at the night sky, but from studying ancient astronomy.
29. As the earth turns, the stars come back to the same place in the night sky every 23 hours, 56 minutes and 4.09 seconds. This is a sidereal day (star day).
30. When Neil Armstrong stepped on the Moon for the first time, he said these famous words: “That’s one small step for a man; one giant leap for mankind.”
31. From the moon, astronauts brought back 380 kg of Moon rock.
32. During the moon landing, a mirror was left on the Moon’s surface to reflect a laser beam which measured the Moon’s distance from the Earth with amazing accuracy.
33. The stars in each constellation are named after a Greek alphabet.
34. The brightest star in each constellation is called the Alpha Star, the next brightest Beta, and so on.
35. The distance to the planets is measured by bouncing radar signals off them and timing how long the signals take to get there and back.
36. Spacecrafts have double hulls (outer coverings) which protect them against other space objects that crash into them.
37. Manned Spacecrafts have life support systems that provide oxygen to breathe, usually mixed with nitrogen (as in ordinary air). Charcoal filters out smells/
38. Spacecrafts toilets have to get rid of waste in low gravity conditions, Astronauts have to sit on a device which sucks away the waste. Solid waste is dried and dumped in space, but the water is saved.
39. A comet’s tail is made as it nears the Sun and begins to melt. A vast plume of gas millions of kilometers across is blown out behind by the solar wind. The tail is what you see, shining as the sunlight catches it.
40. The Shoemaker-Levy 9 comet smashed into Jupiter in July 1994, with the biggest crash ever witnessed.
41. Giant stars have burned all their hydrogen, and so burn helium, fusing helium atoms to make carbon.
42. The constellation of Cygnus, the Swan, contains the very biggest star in the known universe – a hyper giant which is almost a million times as big as the sun.
43. Planet Uranus was discovered by William Herschel, who wanted to name the planet George, after King George III, but Uranus was eventually chosen.
44. The first rockets were made 1,000 years ago in China.
45. Robert Goddard launched the very first liquid-fuel rocket in 1926.
46. Over 100 artificial satellites are now launched into space every year, a few of which are space telescopes.
47. The lower a satellite’s orbit, the faster it must fly to avoid falling back to the Earth. Most satellites fly in low orbits, 300 km from the earth.
48. Hipparchus was the first astronomer to try to work out how far away the Sun is.
49. The red color of Mars is due to oxidized (rusted) iron in its soil.
50. Mars’s volcano Olympus Mons is the biggest in the solar system. It covers the same area as Ireland and is three times higher than our Mount Everest.