Sol

Sol, also known as the Sun, is the main star in the Sol System. It is an average sized star and is the main source of light on Earth as well as other planets in the Sol System. sol is also the shield world that the forerunners were supposed to take refuge in. No one knows for sure what happened, but it is assumed the forerunners not getting to sol before the Halo activation is because of Mendicant Bias, a contender - class forerunner AI.