Planets:

Mercury 

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Closest to the sun, second smallest, and the fastest moving planet is Mercury – it zips around the Sun in 88 days. It is a lifeless and dry world covered with craters. Deep below the surface is a large core of iron. The planet’s gravity is too weak to hold on to an atmosphere and so heat is lost at night. Differences between day and night temperatures can be 600°C (1,080°F)

Venus Evening Star

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In size, mass, density and volume Venus is the planet most similar to Earth. Venus rotates backwards, from east to west, so the Sun would appear to rise in the east and set in the west. Venus is the Brightest Planet of all. Venus's atmosphere is so thick that the pressure on the surface is 90 times that of the Earth – enough to crush a car completly flat.

Earth Blue Planet

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Earth is a watery planet-70 % of its surface appears blue and the only one that can support life. From space, astronauts have observed cities, forest fires, roads, airports, dams and other large structures, such as the Great Pyramid and the Great Wall of China.

Mars Red Planet

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Several space probes have flown past or landed on Mars, Providing information on its atmosphere and features, such as the volcano Olympus Mons.This stands 27km high – more than three times the height of Mount Everest. Mars has the largest dust storms in the Solar System. Sometimes they can cover the entire planet (far right). Mars has ice caps at each pole, which are made of both ice & solid carbon dioxide (dry ice).

Jupiter King of the planets

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Sometimes called the king of the planets, Jupiter is the largest planet in the Solar System and is big enough to contain more than a thousand Earths. Jupiter may be big but it spins at incredible speed. It turns right round in less than 10 hours – compared with 24 for the Earth. Four of its many moons were among the first ever astronomical discoveries made with a telescope, by Galileo in 1610. More were identified by later astronomers and in 1979 by the space probe Voyager 2.

Saturn Ringed Planet

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Saturn is the second largest planet but the least dense. Its distinctive rings are made of pieces of ice and rock which were probably parts of comets and asteroids. These rings are being examined by the joint NASA/European Space Agency project Cassini/Huygens. Launched in 1997, Cassini began a four-year orbit of the ringed planet in July 2004.

Uranus 

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In summer on Uranus, the Sun does not go down for 20 years! It just keeps on going round and round in the sky. In winter, it’s dark on Uranus for 20 years! Uranus has rings like those of Saturn, but they are visible only with a powerful telescope. Rings of Uranus are discovered in 1976.

Neptune 

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The orbits of Neptune and Pluto cross each other. Neptune is the furthest of the nine planets currently, and for 20 years of every 248. Surface winds are the strongest of any planet at up to 2,000km/h. Neptune’s year is so long that it has not completed an orbit round the Sun since its discovery and will not until 2011.

Pluto 

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Though discovered by an American, Pluto’s name was suggested by an 11-year-old British school girl, Venetia Burney. In 2015, a spacecraft will visit Pluto for the first time.

Earth's Moon

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The Earth’s Moon has no atmosphere or wind, and the dust on its surface never moves. So the footprints left in 1969 by the Apollo astronauts are still there today, perfectly preserved.

Earth's Moon is the most familiar and also the largest satellite in relation to its planet in the entire Solar System. It is the first body in the Solar System on which vehicles from Earth landed, and the only one to be explored by humans.

• The word month comes from the Moon, which takes roughly a month to go around the Earth.