Dyson spheres and the quest for alien megastructures

There are three ways to look for evidence of alien technological civilizations. One is to look out for deliberate attempts by them to communicate their existence, for example, through radio broadcasts. Another is to look for evidence of them visiting the Solar System. And a third option is to look for signs of large-scale engineering projects in space.

A team of astronomers has taken the third approach by searching through recent astronomical survey data to identify seven candidates for alien megastructures, known as Dyson spheres, “deserving of further analysis.”

This is a detailed study looking for “oddballs” among stars – objects that might be alien megastructures. However, the authors are careful not to make any overblown claims. The seven objects, all located within 1,000 light-years of Earth, are “M-dwarfs” — a class of stars that are smaller and less bright than the Sun.

Dyson spheres were first proposed by the physicist Freeman Dyson in 1960 as a way for an advanced civilization to harness a star’s power. Consisting of floating power collectors, factories and habitats, they’d take up more and more space until they eventually surrounded almost the entire star like a sphere.

What Dyson realized is that these megastructures would have an observable signature. Dyson’s signature (which the team searched for in the recent study) is a significant excess of infrared radiation.

That’s because megastructures would absorb visible light given off by the star, but they wouldn’t be able to harness it all. Instead, they’d have to “dump” excess energy as infrared light with a much longer wavelength.

Unfortunately, such light can also be a signature of a lot of other things, such as a disc of gas and dust, or discs of comets and