The Vartan Nebula was a nebula mentioned throughout the Future series. Emperor Tachyon exiled all surgeons on Igliak to his "4-Star Penal Colony" in the Vartan Nebula."
Later in A Crack in Time, Mac Mackeroy said that the Agorian Battleplex was the most explosive place on that side of the nebula. Also in the Battleplex itself, the description in one of the challenges said that they had the meanest Elite Hydra Tank on that side.
Then in All 4 One, while exiting the orbit of Magnus, Lawrence mentioned that the Polaris Defence Force had set course for the Vartan Nebula.