Gravity Well
A 'Gravity Well' Is the term used to describe the gravitational force of a massive object. Most human Slipspace drives can't 'Jump' inside a Gravity Well. It is also mentioned in Halo Wars: Campaign: Theater Mode: "One Less Sun In The Universe", where the sun in the Micro Dyson Sphere/Shield World 'goes supernova', just before Captain Cutter plans for the UNSC Spirit Of Fire to leave, but the expanding gravity well of the presumable Forerunner-Made Star is too strong. Captain Cutter Then asks Serena to plot a course around the sun, to slingshot using the gravity well, through the small gap of an entrance to the Micro Dyson Sphere and out of the Shield World.