<text><span class="style10">he Sun and the Solar System (1 0f 6)</span><span class="style7">The Sun, the principal source of light and heat for planet Earth, is a very ordinary star, situated near the edge of a spiral arm about 30 000 light years from the center of the Galaxy. The Sun is the center of the Solar System, which includes at least nine major planets and their satellites, together with interplanetary material and thousands of minor planets, comets and meteoroids.The Sun mainly consists of the gases hydrogen and helium. At its center is a vast nuclear reactor whose temperature is at least 14 million deg C (25 million deg F). The Sun produces energy by nuclear fusion, a process in which hydrogen is converted into helium.The Sun is losing mass at a rate of 4 million tons per second, but its total mass is 2 x 10 to the power of 27 tons, which is 330 000 times that of the Earth and 745 times that of all the planets put together. The diameter of the Sun is 1 392 000 km (863 000 mi) - 109 times greater than that of the Earth - and its volume is 1 300 000 times that of the Earth.</span></text>
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<text><span class="style10">he surface of the Sun</span><span class="style7">, seen here in a false- color extreme ultra- violet image, taken by the Skylab space station in 1973. At the top a huge solar prominence - some 500 000 km (300 000 mi) in height - leaps up through the Sun's atmosphere.</span></text>
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<text>ΓÇó STARS AND GALAXIESΓÇó THE INNER PLANETSΓÇó THE OUTER PLANETS</text>
