The presence of dark energy in our universe is causing space to expand at an accelerating rate .
As a result , over the next approximately 100 billion years , all stars residing beyond the Local Group will fall beyond the cosmic horizon and become not only unobservable , but entirely inaccessible , thus limiting how much energy could one day be extracted from them .
Here , we consider the likely response of a highly advanced civilization to this situation .
In particular , we argue that in order to maximize its access to useable energy , a sufficiently advanced civilization would chose to expand rapidly outward , build Dyson Spheres or similar structures around encountered stars , and use the energy that is harnessed to accelerate those stars away from the approaching horizon and toward the center of the civilization .
We find that such efforts will be most effective for stars with masses in the range of M \sim ( 0.2 - 1 ) M _ { \odot } , and could lead to the harvesting of stars within a region extending out to several tens of Mpc in radius , potentially increasing the total amount of energy that is available to a future civilization by a factor of several thousand .
We also discuss the observable signatures of a civilization elsewhere in the universe that is currently in this state of stellar harvesting .