The coldest 'stars' in the galaxy might actually be alien megastructures

Ever since physicist Freeman Dyson first proposed the concept in 1960, the "Dyson sphere" has been the holy grail of techno-signature hunters. A highly advanced civilization could build a "sphere" (or, in our more modern understanding, a "swarm" of smaller components) around their host star to harvest its entire energy output. We know, in theory at least, that such a swarm could exist-but what would it actually look like if we were able to observe one? A new paper, availa...