Search for Alien Megastructures: What Are Dyson Spheres and How Can They Be Detected?

Some scientists believe that extraterrestrial life exists, and they expand their search using advanced astronomical tools. Some try to find alien civilizations so advanced that they are capable of harnessing the power of a star using a megastructure called Dyson sphere.

What Is a Dyson Sphere?

In 1960, physicist Freeman Dyson published his paper entitled "Search for Artificial Stellar Sources of Infrared Radiation." In this study, he proposed the possibility of having extraterrestrial civilizations so advanced that they have the ability to construct megastructures that are large enough to enclose their parent star. He also indicated that the hypothetical megastructure called Dyson Sphere could be detected based on the "waste heat" emitted at mid-infrared wavelengths.

Infrared signatures are considered viable methods in the Search for Extraterrestrial Intelligence (SETI). For many decades, experts have tried to detect Dyson Spheres, but efforts to find their waste heat signatures have come up empty. This leads some scientists to suggest tweaking the search parameters.

Refined Search for Alien Megastructures

In a new study, astronomy and astrophysics professor Jason T. Wright of the Center for Exoplanets and Habitable World and the Penn State Extraterrestrial Intelligence Center (PSTI) apply the thermodynamics of radiation to Dyson Spheres. He recommends that SETI researchers refine their search by looking for indications of activity, which means that the megastructures be located based on what they could be used for instead of just heat signatures.

A key feature of Wright's research is the Landsberg Limit, a concept that represents the theoretical efficiency limit for harvesting solar radiation. This is an important factor since Dyson's original proposal was based on the idea that all life utilizes free energy gradients.

To date, there are only three all-sky mid-infrared studies that have been conducted, including the Infrared Astronomical Satellite (IRAS), the Wide-field Infrared Survey Explorer (WISE), and AKARI. Traditionally, astronomers have been looking for infrared emission from stars to identify the presence of orbital material warm from the starlight. If it is not the kind of star with orbiting material, then experts can look more closely to see if the material looks like dust or something else.

All attempted searches have been hampered by the fact that there is no underlying theory of what the waste heat would look like since the materials that make the Dyson Spheres remain unknown. Various theoretical models have been proposed regarding their thermal signatures, but these are rather simple and based on numerous assumptions.

Additionally, Wright addressed the engineering challenges of building the megastructures. While Dyson focused on the laws of physics as the only basis for the existence of Dyson Spheres, Wright also considered the engineering practicalities involved in the construction.

From this perspective, a proposal was made that advanced civilizations might be motivated to build sections of a megastructure to gradually increase their habitable volume around a star. These findings can help inform astronomers in their future searches for Dyson structures which are still limited at the moment.