46 Graeae is a special star system located in the Veil Sector. This system was introduced into the game with the deployment of Game Update 18. This is the system where the Dradis Interdiction Duty Missions take place and is only accessible to players when they undertake such a mission. These missions can only be accessed when docked inside the Battlestar Galactica (Colonial), the Basestar in 242 Apollid (Cylon), or an Outpost by selecting the desired Interdiction Duty Map on Dradis and clicking on the "Play Map" button.
It should be noted that you need to have enough map parts to be able to play the Interdiction Missions. If you do not, the mission, and hence the 46 Graeae system is inaccessible.