What is the source of the suns energy? Because light and heat from the sun are the basis of all life on earth, sunlight is absorbed by plants and then transferred into photosynthesis. Almost all living organisms live on the suns energy. It is also the gravitational center of our galaxy. A very important thing about the sun is that it keeps earth in orbit. It also provides warmth for our planet. Its surface temperature is about 5,500 degrees celsius. Any surface at that temperature will generate heat and light.