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  Neptune is the furthest body from the Sun. Surface winds are the strongest of any planet at up to 2,000 km/h. Neptune’s year is so long that it has not comlpleted an orbit round the Sun since its discovery and will not until 2011. Diameter: 49,522 km Mass: 1,024,700,000,000,000 tonnes Average distance from Sun: 4,498,252,900 km Rotation: 16 hours 7minutes Orbit: 164 years 298 days Average temperature: -200.15 ◦ C Moons: 13

      All the satellites of   Uranus are called after characters from either William Shakespeare’s plays or Alexander Pope’s poem The rape of the Lock . Uranus has rings like those of Saturn, but they are visible only with a powerful telescope. Diameter: 51,118 km Mass: 868,320,000,000,000 tonnes Average distance from Sun: 2,870,972,200 km Rotation:17 hours 17minutes Orbit: 84 years 4 days Average temperature -197.15 ◦ C Moons: 27

          Saturn and its rings are being examined by NASA/European Space Agency’s Cassini probe, which reached it in 2004. In 2005 it released the Huygens probe to land on the surface ot Titan and has continued to send back data from its flybys of titan and other moon of Saturn. Diameter: 120,536 km Mass: 5,684,600,000,000 tonnes Average distance from Sun: 1,426,725,400   km Rotation: 10 hours 34   minutes Orbit: 29 years 168 days Average temperature: -139.5 ◦ C Moons: 56

        Jupiter is the largest planet in the solar system and is big enough to contain more than a thousand Earths. Four of its many moons were among the first ever astronomical discoveries made with a telescope, by Galileo in 1610. More were identified be later astronomers and in 1979 by the space probe Voyager 2. The NASA Juno mission to jupiter is planned for launch in 2011. Diameter: 142,984 km Mass: 18,986,000,000,000,000 tonnes Average distance from Sun: 778,412,010 km Rotation: 9 hours 50 minutes Orbit: 11 years 314 days Average temperature: -150 ◦ C Moons: 63

      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 27 km high –more than three times the height of Mount Everest. The latest craft to visit the red planet is Mars Reconnaissance Orbiter, which began a four-year orbit in 2006. NASA’s Phoenix Mars landed in May 2008. Diameter: 6,794 km Mass: 6,421,900,000,000 tonnes Average distance from Sun: 227,940,000   km Rotation: 1.025957 days Orbit: 686.98 days Average temperature: -63 ◦ C Moons: 2

   Earth is a watery planet –70 per cent 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. Diameter: 12,756.3km Mass: 59,720,000,000,000 tonnes Average distance from Sun: 149,600,000 km Rotation: 0.99727 days Orbit: 365.256 days Average temperature: +15 ◦ C Moons: 1

  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. In April 2006 the European Space Agency’s Venus Express spacecraft reached Venus. Japan’s Venus Climate Orbiter PLANET-C will be lauched in 2010. Diameter: 12,103.6km Mass: 48,690,000,000,000 tonnes Average distance from Sun: 108,208,930 km Rotation: 243.0187 days Orbit: 224.7001  days Average temperature: +456.85 ◦ C Moons: 0

  Mercury was named after the speedy messenger of the gods because it seemed to move more quickly than the other known planets. In 2004 NASA launched its MESSENGER probe, which is due to reach Mercury in 2011. Diameter: 4,880 km Mass: 3,302,000,000,000 tonnes Average distance from Sun: 57,909,175  km Rotation: 58,6462 days Orbit: 87.869 days Average temperature: +166.86   ◦ C Moons: 0

    The Solar System was formed about 4,560 million years ago. It is made up of the eight planets –Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune –as well as their moons, comets and other bodies. These all orbit our Sun, to which they are attracted by gravity.

The Sun is 149,597,893 km from Earth and has a diameter of 1,391,940 km. This is more than 100 times larger than Earth. Its mass is equivalent to 99.98 percent of the mass of the entire Solar System. Elements   The sun is mostly made up of two light gases, 75 per cent hydrogen and 23 percent helium, with relatively small quantities of other elements –including metals such as gold. Helium was discovered in the Sun before it was detected on Earth. Its name comes from helios, the Greek word for sun. Temperature   The Sun has  a surface temperature of 5,880 K but it can be 56,000,000 K at its core. At the Sun’s centre, nuclear fusion constantly changes hydrogen into helium, and the energy and heat released from this process rise to the surface. The yellow surface we see is called the photosphere. The corona   The outermost layer of the Sun extends million of kilometers into space but is visible only during eclipses. At a height of  75,000 km in the corona, the temperature may reach  

  In space, Light travels at a speed of 299,792,46 km a second or  1,079,252,956 km an hour. When we look at even the nearest star, we see light that left it more than four years ago. Here are the times it takes light to reach Earth from various bodies in space. Light years     A light year measures distance, not time. Distance in space are often described as light years. The distance light travels in a year. Moon 1.26 seconds. Sun 8 minutes 17 seconds. Furthest planet (Neptune) 4 hours 21 minutes when the planet is at its  maximum distance from Earth. Nearest star 4.22 years distance at which the Sun would no longer be visible to the naked eye 60 years. Most distant sta r in our galaxy 62,700 years. From nearest body outside our galaxy 174,000 years. Furthest visible star 2,309,000 years. Most distant known quasar 14,000,000,000 years.

Groups of stars form patterns in the night sky, which are called constellations. There are 88 known constellations. The sumerians, a Middle Eastern civilization, probably named them, about 5,000 years ago.    The largest is Hydra, the sea serpent, and the smallest is Crux Australis, the Southern Cross. Centaurus, the Centaur. Has the most stars that can be seen with the naked eye(94). Others include Aquila, the Eagle; Canis Major, the Great Dog; and Orion, the Hunter.

    Galaxies are groups of billions of stars held together by the force of gravity. Most are either spiral or elliptical, but some are irregular in shape. The Milky Way   This is the best-known galaxy. The word galaxy comes from the Greek for milk. Before telescopes were powerful enough to prove that they were made up of individual stars, galaxies looked like milky or cloudy areas in the sky. Our Solar System is only one of 100 -200 billion stars in the Milky way, which is 100,000 light years in diameter. The Sun and all the planets take about 200,000,000 years to complete on orbit around its centre. Brightest   The Large Magellanic Cloud, which is visible only in the southern hemisphere, is 170,000 light years from Earth and 39,000 light years in diameter. Largest   The central galaxy of the Abell 2029 galaxy cluster was discovered in 1990. It is 1,070 million light years   distant and has a diameter of

  A star is a luminous body of gas, mostly hydrogen and helium. Stars generate light, which makes it possible for us to see them with a telescope or the naked eye. ·          Brightest   Not counting the sun, the brightest star as seen from   Earth is Sirius, known as the dog star, in the constellation of Canis Major. It has a diameter of 149,598,020 km and is more than 24 times brighter than the Sun, The star LBV 1806 – 20 in the constellation of Sagittarius may be 40 million times as bright as our sun, but dust clouds make it almost invisible from Earth. ·           Largest   The largest star in VY Canis Majoris, which has an estimated diameter of about 1.950 times greater than the sun. For comparison, if it were a football, th sun would be no bigger than a pinhead. ·          Nearest     Proxima Centuari, discovered in 1915, is 4,22 light years (39,953,525,879,212 km) from the Earth. A spaceship moving