One group of scientists thinks that we may already have detected technosignatures from a technological civilization’s Dyson Spheres, but the detection is hidden in our vast troves of astronomical data.

In this sense, ‘advance’ means the kind of almost unimaginable technological prowess that would allow a civilization to build a structure around an entire star. These Dyson Spheres would allow a civilization to harness all of a star’s energy. A Dyson Sphere is a hypothetical engineering project that only highly advanced civilizations could build.