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Back in 1960, the physicist Freeman Dyson publish an unusual paper in the journalScience entitled “Search for Artificial Stellar Sources of Infra-red Radiation.” In it, he outlined a hypothetical structure that entirely encapsulates a star to capture its energy, which has since become known as a Dyson sphere.

The basic idea is that all technological civilizations require ever greater sources of energy. Once the energy of their home planet has been entirely exhausted, the next obvious source is the mother star. So such a civilization is likely to build a shell around its star that captures the energy it produces.

Of course, such a sphere must also radiate the energy it absorbs and this would produce a special signature in the infrared part of the spectrum. Such a source of infrared radiation would be entirely unlike any naturally occurring one and so provide a unique way of spotting such as advanced civilization.

Because Sun-like stars seem the most obvious homes for advanced civilizations, most studies of Dyson spheres have focused on the properties these kinds of systems would have when built within the habitable zone at a distance of about 1 astronomical unit.

These studies have revealed well-known limitations, however. Such spheres tend to be unstable and require huge volumes of material to build. But most problematic of all, anything or anyone on the surface of these spheres would experience low levels of gravity, a problem that could not easily be solved with known physics.

Today, Ibrahim Semiz and Salim Ogur at Bogazici University in Turkey, define an entirely new class of Dyson sphere. Instead of thinking about a sphere around a Sun-like star, Semiz and Ogur consider a sphere built around a white dwarf.

They say that such a sphere would avoid some of the most severe problems and that there are good arguments to think that they might be more common than the ones Dyson originally imagined.

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