Burning bright in the sky, the Sun is the source of all energy!
What is the Sun?
The Sun is the nearest star to the Earth. It's a huge ball of hydrogen gas held together by gravity. In the Sun, hydrogen gas is pressed so close together that it becomes helium gas. This change gives out lots of energy which we experience as heat and light (this is why the Sun is so bright).
The Sun with many solar flares visible
Why do we need the Sun?
We need the Sun for two reasons. Firstly, the heat from the Sun keeps water warm enough not to freeze. Liquid water is needed for life to develop. Secondly, light from the Sun is absorbed by plants for them to grow. We then get this energy when we (or animals) eat plants.