Alien megastructures built to harvest stellar energy or alter the orbits of stars may be physically feasible, according to a new analysis – satisfying both our sci-fi fancies and our innate yearning to not feel so alone in a large, cold Universe. What's more, these immense extraterrestrial constructions could remain stable for untold eons in the right configuration. They might even radiate distinctive technosignatures , allowing astronomers to search for civilizations that have survived long