The sun is the main star in earth's planetary star system. It has been burning for approximately 5 billion revolutionary cycles of Earth and will continue burning for about the same amount of time. The sun is the base of the food chain for earthlings because it enables the plants on the planet to photosynthesise. At the end of its solar cycle, it will turn into a red giant, engulfing all of the planets in the earth's solar system inside of the asteroid belt.