Free Astronomy Magazine September-October 2024

SEPTEMBER-OCTOBER 2024 At that time, Giuseppe Cocconi and Philip Morrison pioneered the search for radio signals emitted more-or-less voluntarily by extra- terrestrial civilizations, while Nikolaj Kardašëv hypothesized that ex- tremely advanced alien technologies could have exploited the energy emitted by stars in ways unimagin- able to us. Dyson enriched this sce- nario by supporting the possible existence in other planetary systems of spherical, shell-shaped megas- tructures built around single stars and capable of harnessing most of the energy those stars emit. At the beginning of the 1960s, all this must have seemed like science fiction, as we knew very little about our own solar system and absolutely nothing about other possible similar systems. However, Dyson’s hypothe- sis could (and can) be verified since those megastructures, today known as “Dyson Spheres,” would produce two effects that are easily recogniz- able by the observer: they likely completely hide the visible light of the stars they surround and, by heat- ing up internally, they radiate from the external surface a non-negligi- ble quantity of infrared light, which A fictional representation of a Dyson sphere. This type of megastructure, hy- pothesized in 1960 by the Anglo-American physicist and mathematician Freeman John Dyson, could appear completely closed or, as in this case, in the form of con- centric bands. Their pres- ence could be noticed by an excess of infrared radiation apparently coming from the star, or by an anomalous light curve of the latter. [Getty images]