Is the solar-system sized bubble in the Consellation Cygnus a planetary nebulae or could it be an “AC” or astroengineering construction, also known as a Dyson sphere, named after Freeman Dyson of the Princeton Institute for Advanced Study who proposed the theory? Dyson’s thought experiment suggested that in our search for advanced extraterrrestrial civilizations that Instead of radio signals we should look for spheres, which are artificial mega structures that enclose the orbit of a star, fabricated from the material of that solar system. The key is to distinguish a Dyson sphere from natural dust components. The Dyson sphere is the marker of what Kardashev calls a Type 2 civilization, which is capable of using up all the energy produced by a star. A Type three civilization uses up all the energy produced by a galaxy.”

ACs are expected to have spectra similar to the black-body spectra because they re-emit all the energy that they absorb, although in the infrared range.

“Fermi Bubbles” is the term used by Richard Carrigan at the Fermi National Accelerator Laboratory in his latest work on the search for artifacts like Dyson spheres or Kardashev civilizations. A Fermi bubble according to Carrigan would grow as the civilization creating it colonized space. Carrigan notes that, as Carl Sagan and others have observed, that the time to colonize an individual system is small compared to the travel time between stars. A civilization could engulf its galaxy on a time scale comparable to the rotation period of the Milky Way, or every 225–250 million years, and perhaps, fewer.

According to Carrigan, of the 11,224 potential sources of low range emissions identified that might be a manifestation of Dyson spheres in the Milky Way there are only 16 that have strong potential.

In a recent post at Centauri Dreams they suggest that if we’re going to get lucky with SETI, it’s probably going to be through the reception of an interstellar beacon rather than the chance detection of an electronic emission from space. Former NASA SETI signal detection analyst Bob Krekorian proposes that a space-faring species will put its transmitter inside the habitable zone, designed to exist as close to the parent star as feasible to take advantage of the huge amounts of energy available there.

Casey Kazan

http://www.dailygalaxy.com/my_weblog/2010/03/the-cygnus-bubble-natural-or-artificial.html