From Halopedia, the Halo wiki
At least four (Ansket IV)
The Ansket system is a planetary star system.
The Ansket system is composed of a single star orbited by at least four planets. The fourth of these is a terrestrial world, Ansket IV. It once was home to a Covenant hydro-processing facility but this location later became a United Nations Space Command forward operating base. The Banished attacked the UNSC on Ansket IV around mid-2553.