In 1964, Soviet astronomer Nikolai Kardashev conceived the levels of extraterrestrial civilizations based on their ability to control different energy technologies, categorizing them into different civilization types. A cosmic civilization that can control the energy of stars in its planetary system is classified as a Type II civilization, capable of harnessing more than 10 billion times the energy output of our own Sun.
As early as the 1960s, physicist Freeman Dyson proposed the concept of a “Dyson Sphere,” a hypothetical megastructure built around a star to maximize energy collection. Though this idea was legendary, astronomers have since discovered celestial objects with similar features using infrared space telescopes. Stars shrouded in dust clouds can appear like “Dyson Spheres.”
According to observations from NASA’s Wide-field Infrared Survey Explorer (WISE), astronomers have identified stars enveloped in cosmic dust clouds. In the 1970s, astronomers conducted an infrared survey of 250,000 celestial objects and discovered 17 objects with features resembling Dyson Spheres. Richard Carrigan, a scientist at the Fermi National Laboratory, explained, “We can imagine that super-civilizations would first colonize the energy-rich regions of their own planetary systems and then expand to galaxies to obtain maximal energy.” Carrigan hoped to observe traces of giant “Dyson Spheres” in nearby galaxies. For Kardashev Type II civilizations, which not only transform individual stars into Dyson Spheres but possibly colonize entire star clusters for energy, the effects would be observable. For instance, we might detect anomalous dark regions in the galaxy, and some of the star’s energy would leak in the form of infrared radiation, creating observable bright emissions in infrared space telescopes, or they could be interpreted as thermal radiation from Dyson Sphere surfaces. The Andromeda Galaxy, M51, is considered an ideal place to search for Dyson Spheres. The Hubble Space Telescope and the Spitzer Infrared Space Telescope from NASA will observe countless star systems within the galaxy, tracking stars hidden by dust clouds. Carrigan roughly estimated that there should be no unexplained “bubbles” or gaps in the M51 galaxy. Giant elliptical galaxies, free from dust clouds, would present a strange phenomenon if unusual dark gaps were found within them. However, elliptical galaxies are at least 60 million light-years away, requiring larger space telescopes. The Hubble telescope currently provides sufficient resolution. In Kardashev’s classification, Type III civilizations, capable of harnessing all the energy within their entire galaxy, are the most advanced. Yet, existing astronomical observations have not identified any unexplained energy phenomena within entire galaxies. So, Type III civilizations either do not exist or have not appeared at least as of now.