The sun is the star that is in the middle of our Solar System, our sun is very normal compared to many other stars, it's not really hot for a star and it is not really big for a star, but it is still a star and it is very important for our lives. The sun is almost a perfect sphere, with a diameter of approxamately 1.4 million killometers which is almost 100 times as big as the earth. The core of the sun contains hot plasma, which is kept together by it magnetic field. The main part of the sun is made of hydrogen, around 3/4 and the rest is mostly helium, and than there is a very small amount (which still is about 5.500 times the mass of earth) of oxygen, carbon neon and iron among some other elements. Almost all the energy from the sun originates from nucleur fusion, every second 700 tons of hydrogen is converted to about 695 tons of helium and energy. According to Einsteins law E=mc² the sun produces 5000*9*10¹⁶= 4.5*10²⁰ joules/second this is the 5 ton of hydrogen that is converted to energy, this is the energy we feel everyday and use everyday. The Sun is now aobut 4.6 billion years old, it formed because of a collapse in a molecular cloud, almost all of the matter inside this cloud, becuase of this high pressure and heat in the middle of this cloud it initianted molecular fusion which generates all the light and heat of the sun. Almost every star in the universe forms this way. The sun is in principle white, but because of the scattering of blue lgiht it appears as yellow on the earth, the sun has a temperature fo about 5500 °C. The sun becomes lighter for about 10% every billion years. This and the increase in the suns radius will make the earth unliveable in the next 1 untill 1.5 billion years. The sun will also become warmer, this will let the temperature on earth rise, which will cause water to escpae the atmosphere and take away all the water on the earth. Another thing that will make the earth unliveable is the expansion of the sun, the sun will transform into a red giant which radius will be about 250 times bigger than the radius it has now.