[space] Astronomers actually scan the sky for stars that look slightly dimmer than they should. This hypothetical megastructure is why

[Di87]

In 1960, physicist Freeman Dyson published a short paper suggesting that any sufficiently advanced civilization would eventually need more energy than its home planet could ever provide, and the obvious place to get more is the star itself. He proposed that such a civilization might build a vast system of structures around its star specifically to capture that energy, and crucially, he pointed out that doing so would leave a detectable fingerprint, since a star surrounded by heat absorbing structures would radiate an unusual amount of infrared light

Dyson later clarified that he never actually imagined a solid shell enclosing a star, which is mechanically impossible and would likely be torn apart by the star's own gravity and rotation. What he had in mind, borrowed loosely from a 1937 science fiction novel called Star Maker, was a loose swarm of independent objects, solar collectors or habitats, all orbiting the star on their own separate paths. Fiction has mostly run with the more dramatic solid shell version anyway, which is why shows and books tend to depict something that real physicists consider the least plausible of the possible designs

Building anything close to a full Dyson swarm around our own sun is completely out of reach for humanity today, there simply is not enough raw material in the entire solar system to construct something like this without importing matter from other star systems entirely, something we have no technology to even attempt. Still, the search continues in a modest, genuinely scientific way, astronomers occasionally flag unusually dimmed or infrared bright stars as candidates worth a closer look, a search that has turned up strange stars but, so far, no confirmed alien engineering project

A Dyson sphere harvests the energy of starsearthsky.org