The sun.
The sun is just like the other star that we see in the sky. It seem like a large around red ball only because we are much closer to Sun then to any other star. The sun is, in fact our coldest star. It is 149.6 million km away from the Earth. Some other stars maybe much larger and brighter than the sun, but they are so far away that they only look like point of light in the night sky.
At round 13,92,000 kilometres wide , the sun's diameter is about 110 time wide then the earth. The sun is so big that more than 1 million Earth could fit in it.
The sun is a ball of hot, glowing gases. Its its surface temperature is around 5,500°C . It gets hotter as we go deeper. The sun is so hot that the planets millions of kilometers away from it can feel its heat. Without the sun, our planet would simply be a dark, frozen world.
Besides heat, the sun also provides us with light. Without the sun come are there could be no daylight. It takes about 8 minute for sunlight to reach the earth. This means that we see the sunset 8 minutes after the event has actual take place.