What is a Dyson sphere? (2024)

A Dyson sphere is a theoretical mega-engineering project that encircles a star with platforms orbiting in tight formation. It is the ultimate solution for living space and energy production, providing its creators ample surface area for habitation and the ability to capture every bit of solar radiation emanating from their central star.

Why build a Dyson sphere?

Why would anyone construct such a bizarre monstrosity? According to British-American theoretical physicist Freeman Dyson, who first speculated about these putative structures in 1960, an intelligent alien species might consider the undertaking after settling on some moons and planets in their local stellar neighborhood. As their population increased, these extraterrestrials would start to consume ever-greater amounts of energy.

Assuming this alien society's populace and industry grew at a modest 1% per year, Dyson's calculations suggested that the aliens' area and energy needs would grow exponentially, becoming a trillion times larger in just 3,000 years. Should their solar system contain a Jupiter-size body, the species' engineers could try to figure out how to take the planet apart and spread its mass in a spherical shell.

By building structures at twice the Earth-sun distance, the material would be sufficient to construct a huge number of orbiting platforms 6 to 10 feet (2 to 3 meters) thick, allowing the aliens to live on their star-facing surface. "A shell of this thickness could be made comfortably habitable, and could contain all the machinery required for exploiting the solar radiation falling onto it from the inside," Dyson wrote.

But after absorbing and exploiting the solar energy, the structure would eventually have to reradiate the energy or else it would build up, causing the sphere to eventually melt, according to Dyson. This means that, to a distant observer, the light of a star wrapped in a Dyson sphere might appear dimmed or even entirely darkened — depending on how dense the orbiting platforms were — while glowing curiously bright in infrared wavelengths that aren't visible to the naked eye.

Do Dyson spheres exist?

Because of their infrared radiation, Dyson spheres are considered a type of technosignature — a sign of activity that distant astronomers could use to infer the existence of intelligent beings in the universe, according to a NASA report. A handful of Earth-based researchers have scanned infrared maps of the night sky in hopes of spotting Dyson spheres, but so far, nobody has seen anything out of the ordinary.

In 2015, astronomer Tabetha Boyajian, then at Yale University, reported on the mysterious dimming of light from a star called KIC 8462852, whose irregular flickering looked like nothing researchers had ever seen before. Other scholars suggested the weird light dips could result from a partially built Dyson sphere, and the idea caused a media sensation. Campaigns to look for other signs of technological activity from the entity, which came to be known as Tabby's star in honor of Boyajian, have turned up empty, and most researchers now think the object's light patterns have some kind of nonalien explanation.

For decades, Dyson spheres have been a staple of science fiction media. As far back as 1937, author Olaf Stapledon's novel "Star Maker" (Methuen Publishing, 1937) described how systems in one particular galaxy were "surrounded by a gauze of light traps, which focused the solar energy for intelligent use, so that the whole galaxy was dimmed," a portrayal that Dyson acknowledged as an influence on his thinking. In his novel "Ringworld" (Ballantine Books, 1970), writer Larry Niven described a ring-shaped artificial structure encompassing a star, while a 1992 episode of "Star Trek: The Next Generation" featured a star surrounded by a rigid shell.

Whether such fanciful structures exist outside the human imagination still remains to be seen. In his conjectures, Dyson was not suggesting that all technological societies would enact this outlandish project. Rather, some might have, he reasoned, and therefore, it would be valuable for human astronomers to search for these colossal examples of intelligent minds.

Additional resources:

• Read more about Dyson spheres on EarthSky.org.
• Learn more about technosignatures and the search for intelligent life, from NASA's astrobiology program.
• Watch: Should We Build a Dyson Sphere? from PBS Space Time.