Algol (Earth-5875)

Algol, designated Beta Persei (β Persei, abbreviated Beta Per, β Per), and known colloquially as the Demon Star, is a bright binary star system in the constellation of Perseus. It was one of the first non-nova variable stars to be discovered by humanity.

History
In 2548, the system was invaded by the Covenant, which attacked the human colony Algolis. During the firefight, the UNSC Marine unit Hades Corps were tasked with demolishing the Weapons Research Facility T12A to prevent it from falling into the Covenant's hands, while the last civilian survivors of the planet were evacuated. The UNSC The Heart of Midlothian was en route to the planet to secure the base's HRUNTING/YGGDRASIL Mark I ADS before it was attacked. All Covenant forces attacking the base were pulverized by the sacrifice of Ghost, who activated the Mark I's self-destruct system.