Dyson spheres around black holes may reveal alien civilizations, scientists say

Dyson spheres around black holes may reveal alien civilizations, scientists say
Dyson spheres around black holes may reveal alien civilizations, scientists say

One of the biggest questions we ask ourselves about the universe is: Are we alone as a technologically advanced species? This raises other questions: If aliens exist, what does their technology look like? And, importantly, how can we detect them?

The new study provides some answers to these questions - at least when it comes to technology such as a super-powerful energy collector called the Dyson Sphere, which collects energy from a black hole.

"In this study, we are looking at the energy source of a well-developed Type II or III civilization. They need a more powerful source of energy than their own Sun," the researchers write in their paper.

"The accretion disk, corona and relativistic jets could be potential powerhouses for a Type II civilization. Our results show that for a black hole of stellar mass, even with a low Eddington coefficient, the accretion disk can produce hundreds of times more luminosity than a main sequence star."

The concept of the Dyson sphere was popularized by theoretical physicist Freeman Dyson in the 1960s as a solution to the problem of energy consumption exceeding the capabilities of the planet of civilization. The sphere itself is built around the star of the planetary system - a megastructure that collects the energy of the star from the source.

In his work, Dyson suggested that infrared radiation of thermal energy could be released during the capture and transformation of stellar energy by Dyson structures, which hypothetically could betray the presence of these hypothetical structures. This infrared signature, if we could detect it, would allow us to detect alien civilizations.

Led by astronomer Tiger Yu-Yang Xiao from Qing Hua National University in Taiwan, the team of researchers has taken a step further. What if a Dyson sphere (or a Dyson ring, or a Dyson swarm) were located around a black hole? Will this work, and what can we find from here on Earth?

The only thing black holes are known for is their powerful gravitational field, which absorbs everything that comes close to them and does not release it back (which we can detect).

Therefore, you are probably wondering how something can be learned from such a monster. It turns out that in the extreme environment around a black hole, there are a number of processes from which energy can be extracted.

In their paper, the team looks at a number of such processes: an accretion disk of material orbiting a black hole, which is heated by friction to millions of degrees; Hawking radiation, theoretical black body radiation emitted by black holes, proposed by Stephen Hawking.

Other potentially significant phenomena that could contribute include spherical accretion, a corona of magnetized plasma between the inner edge of the accretion disk and the event horizon, and jets launched at relativistic speeds from the poles of active black holes.

Based on models of black holes, which are 5, 20 and 4 million times the mass of the Sun (this is the mass of Sagittarius A *, the supermassive black hole in the center of the Milky Way), Xiao and his colleagues were able to determine that the sphere of satellites could efficiently collect energy from some of these processes.

"The highest luminosity can be collected from the accretion disk, reaching 100,000 times the luminosity of the Sun, which is enough to sustain a Type II civilization," the researchers write.

"Moreover, if the Dyson sphere collects not only electromagnetic radiation, but also other types of energy (for example, kinetic energy) from the jets, then the total collected energy will be about five times more."

Such structures could be found in multiple wavelengths, the researchers found, with hotter Dyson spheres being more visible in the ultraviolet and colder ones in the infrared, as Dyson himself predicted.

However, given that active black holes already emit a lot of radiation in both of these wavelength ranges, detecting Dyson excess may be easier said than done.

The team speculates that taking other measurements, such as changes in light when a black hole is slightly affected by the sphere's gravity, could help reveal where these structures might be hiding.

The study was published in the Monthly Notices of the Royal Astronomical Society.

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