Dyson Sphere

Dyson Sphere

A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output.

Proponents of solar power know that only a tiny fraction of the sun’s total energy strikes the Earth. What if we, as a civilization, could collect all of the sun’s energy? If so, we would use some form of Dyson sphere, sometimes referred to as a Dyson shell or megastructure. Physicist and astronomer Freeman J. Dyson first explored this idea as a thought experiment in 1960. Dyson’s two-page paper in the journal Science was titled Search for Artificial Stellar Sources of Infrared Radiation 

 because he was imagining a solar-system-sized solar power collection system not as a power source for us earthlings, but as a technology that other advanced civilizations in our galaxy would, inevitably, use. Dyson proposed that searching for evidence of the existence of such structures might lead to the discovery of advanced civilizations elsewhere in the galaxy

Freeman J.Dyson

In recent years, astronomers explored that possibility with a bizarre star, known to astronomers as KIC 8462852 – more popularly called Tabby’s Star for its discoverer Tabetha Boyajian. This star’s strange light was originally thought to indicate a possible Dyson sphere. That idea has been discarded, but, in 2018, other possibilities emerged, such as that of using the Gaia mission to search for Dyson spheres.[Gaia mission is explained below]

The concept of space-based solar power has been around for a long time, but no one has ever conceived of an array that’s billions of square kilometers in size. A Dyson sphere/swarm would go even farther, encircling or enveloping the entire Sun. (NASA)

Here on Earth, the amount of energy available to us is determined by the amount of sunlight striking our planet’s surface. At Earth’s distance from the Sun, that equates to approximately 1300 watts per square meter, which drops to around 1000 if you force the light to go through the atmosphere. If we were to cover the space above Earth’s atmosphere with solar panels, we could collect around 166 million gigawatts of power, continuously, over the entire Earth. This is a tremendous amount of power: about a second’s worth of this could power humanity’s uses on Earth for an entire year. But it’s only a tiny fraction of the energy produced by the Sun. If we needed more, there are ways to do it.

All of this is just to say that Dyson spheres – while in the realm of science fiction and scientific possibility during the 20th century – now seem real enough to astronomers that some are scrutinizing particular stars, looking for signs of them

The central dot in this image represents a star. The simplest form of Dyson sphere might begin as a ring of solar power collectors, at a distance from a star of, say, 100 million miles. This configuration is sometimes called a Dyson ring. Image via Wikimedia Commons.

So what are these odd megastructures, these Dyson spheres? Originally, some envisioned a Dyson sphere as an artificial hollow sphere of matter around a star, and Dyson did originally use the word shell. But Dyson didn’t picture the energy-collectors in a solid shell. In an exchange of letters in Science with other scientists, following his 1960 Science article, Dyson wrote: 

"A solid shell or ring surrounding a star is mechanically impossible. The form of ‘biosphere’ which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star. "

As time passed, a civilization might continue to add Dyson rings to the space around its star, creating a relatively simple, but incredibly powerful, Dyson sphere. Image via Wikimedia Commons.

And of course science fiction writers have had a field day writing about Dyson spheres. Dyson himself admitted he borrowed from science fiction before he began his technical exploration of the idea of a megastructure gathering energy from its star. Olaf Stapledon first mentioned this idea in his 1937 science fiction novel “Star Maker”, which Dyson apparently read and used as inspiration. 

The European Space Agency has just released a huge suite of data from the most powerful satellite ever to map and survey the stars in the Milky Way: Gaia. They’ve recorded information about a whopping 1.7 billion stars in our galaxy, allowing us to create the most sophisticated 3D map of the stars in our galaxy ever. It isn’t all the stars, but it’s orders of magnitude more than were ever recorded previously, including in the first Gaia data release.

 

One of the great things that Gaia was able to measure was the color and magnitude of a great many stars, from faint red dwarfs (and even nearby brown dwarfs) to stellar corpses like white dwarfs all the way up to main sequence stars and the giants and supergiants that are among the most luminous of all. But Gaia doesn’t just observe visible light, but near-infrared as well, meaning that objects invisible to human eyes will be revealed. This includes ultra-cool stars of both the giant and dwarf variety. And, if they existed, it could also include Dyson spheres, assuming they had specific temperature/luminosity profiles. Here’s the classic “color-magnitude” diagram on the left, and what Gaia has observed (below) on the right. 

Artist’s concept of a Dyson sphere

 
A Dyson sphere would consist of orbiting solar collectors in the space around the star of an advanced civilization. The goal would be to ensure a significant fraction of the star’s energy hits a receiving surface where it could be used to the civilization’s benefit. Freeman J. Dyson, who in 1960 became the first scientist to explore this concept, suggested that this method of energy collection be inevitable for advanced civilizations.