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Full Version: Alien 'Dyson spheres' could be harvesting the power of black holes (engineering)
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EXCERPTS: . . . During a coffee break, astronomer Tiger Yu-Yang Hsiao of National Tsing Hua University in Taiwan and his colleagues read a paper about Dyson spheres and began wondering if it were possible to build one around a black hole instead of a star.

[...] While we normally think of them as being dark and all-consuming, black holes can radiate incredible amounts of energy ... Material often forms a disk as it falls into a black hole's maw, much like water circling a drain.

As the gas and dust in this disk spin and bump against each other, they heat up through friction, sometimes to millions of degrees, producing light in the X-ray portion of the electromagnetic spectrum, Hsiao said...

[...] Because black holes smoosh a gargantuan mass into a tiny area of space, they are smaller than stars and therefore potentially easier to encircle. A species that chooses to "build a Dyson sphere around a black hole can save a lot of material," Hsiao said.

Aliens could place a large satellite in a stable orbit around a black hole and then collect X-ray energy using something akin to solar panels [...] They might also build a ring-like structure around the black hole or totally surround it with platforms, much like in Freeman Dyson's original proposal...

In either case, a black hole could radiate up to 100,000 times more energy than a star like the sun, meaning that a celestial species would have a lot of power to work with, the researchers wrote in a paper published July 1 in the journal Monthly Notices of the Royal Astronomical Society.

After being absorbed and used, the energy from a cosmic object would have to be reradiated or else it would build up and eventually melt the Dyson sphere, as Dyson noted in his 1960 paper. This energy would be shifted to longer wavelengths, so a Dyson sphere around a black hole might give off an unexplainable energy signature in the ultraviolet or infrared, the researchers said... (MORE - missing details)