This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The latest Swedish-led search for technosignatures in the form of Dyson spheres has again come up empty-handed. The two latest stellar candidates in the hunt for such hypothetical extraterrestrial technology have been eliminated as Dyson spheres.
Project Hephaistos, a Uppsala University-led initiative, used NASA's James Webb Space Telescope to observe two new Dyson sphere candidates. The Webb telescope obtained images and spectra of two M-dwarf stars, as noted in two papers submitted to the journal Monthly Notices of the Royal Astronomical Society (MNRAS). The work is currently published on the arXiv preprint server.
Dyson spheres are hypothetical megastructures constructed around stars to harvest radiation energy, possibly for the purpose of powering habitats, vessel propulsion, computing or transmitting long-range signals, the MNRAS authors note. The primary technosignature of such structures is the waste heat emitted, usually assumed to be detectable as excess radiation in the infrared, they write. Most such putative waste heat emissions would show up in the mid-infrared spectrum.
"We find that the infrared excess does not originate from Dysonian megastructures, or other radiation mechanisms close to these stars, but from background galaxies projected to be within an arcsec of the M dwarfs," the MNRAS papers' authors write. One has a mid-infrared spectrum consistent with being a Hot Dust Obscured Galaxy (Hot DOG), they note. The other galaxy has what the authors call an extended morphology with bright knots and a spectrum consistent with a dusty starburst, they note.
These latest results point out the extreme difficulty of looking for technosignatures of any sort, whether from highly advanced Kardashev III- or IV-type civilizations capable of harnessing whole galaxies or a Kardashev I- or II-type civilization capable of harnessing the energy of a single star. "This is a follow-up with the Webb telescope to observe two stars that we identified in a survey of some 1 million stars within about 1,000 light-years of Earth," Andreas Korn, a senior lecturer in astrophysics at Uppsala University in Sweden and a member of the Project Hephaistos team, told me in Stockholm. That survey was first conducted with the European Space Agency's Gaia satellite and NASA's WISE (Wide-field Infrared Survey Explorer) mission.
The aim was to look for stars that have surprisingly low fluxes in the optical and surprisingly high fluxes in the infrared. As Korn notes, such a combination is seen as a potential technological signature of an extraterrestrial civilization, referred to in general terms as a Dyson sphere. The two stars that were initially the most promising were relatively faint M-dwarf stars, around 15th magnitude and estimated to be a few billion years old.
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