The sun is a medium-sized star. It is light yellow in colour. It is the largest body in the solar system. Its diameter is about 1392000 km and it is situated at about 2.5 x 10 14*4 light years away from the galactic center of the Milky Way. The distance between the sun and the earth is about 1.5 x 10*8 km. About 75 percent of the mass of the sun is made up of hydrogen and slightly lesser than 25 percent of the mass is made up of helium. The rest is composed of small amounts of carbon, oxygen and other elements. The sun’s mass makes up 99.8 percent of mass of the entire solar system. The temperature of its surface is 6 x 10*3 Deg. C and that of the core is 1.5 x 10*3 Deg. C. Its mass is about 2 x 10*30 kg. It takes 2.5 x 10*8 years to complete one revolution around the galactic center and the period is called one cosmic year.
I consists of 3 layers. They are photosphere, chromosphere and corona. Photosphere, is the central hottest and the thinnest layer. Chromosphere is thicker than photosphere and can be seen during the total solar eclipse only and the corona is the thickest layer. It is spread about millions of km around the chromosphere.
The sun produces most of the energy in the core. It does so by means of nuclear fusion. During fusion hydrogen nuclei collide and fuse together to form helium nuclei. Scientists estimate that there is enough hydrogen inside the sun to continue the fusion for another five billion years.
