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- Suazo, Matias, et al.
(författare)
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Project Hephaistos - I. Upper limits on partial Dyson spheres in the Milky Way
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 512:2, s. 2988-3000
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Tidskriftsartikel (refereegranskat)abstract
- Dyson spheres are hypothetical megastructures built by advanced extraterrestrial civilizations to harvest radiation energy from stars. Here, we combine optical data from Gaia DR2 with mid-infrared data from AllWISE to set the strongest upper limits to date on the prevalence of partial Dyson spheres within the Milky Way, based on their expected waste-heat signatures. Conservative upper limits are presented on the fraction of stars at G <= 21 that may potentially host non-reflective Dyson spheres that absorb 1-90 per cent of the bolometric luminosity of their host stars and emit thermal waste-heat in the 100-1000 K range. Based on a sample of approximate to 2.7 x 10(5) stars within 100 pc, we find that a fraction less than approximate to 2 x 10(-5) could potentially host similar to 300 K Dyson spheres at 90 per cent completion. These limits become progressively weaker for less complete Dyson spheres due to increased confusion with naturally occurring sources of strong mid-infrared radiation, and also at larger distances, due to the detection limits of WISE. For the similar to 2.9 x 10(8) stars within 5 kpc in our Milky Way sample, the corresponding upper limit on the fraction of stars that could potentially be similar to 300 K Dyson spheres at 90 per cent completion is less than or similar to 8 x 10(-4).
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| 4. |
- Suazo, Matías
(författare)
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Searching for Dyson spheres in the Milky Way
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The quest to find intelligent extraterrestrial life has captivated humanity for a long time, motivating the development of various strategies to search for signs of advanced civilizations. These strategies comprise multiple techniques and span different regions of the electromagnetic spectrum. One approach considers the existence of Dyson spheres, one specific type of megastructure theorized by Freeman Dyson over sixty years ago. Dyson hypothesized that advanced civilizations would eventually outgrow their planetary resources and aim to collect the energy of their central star by building colossal structures to harness the star's energy. The potential existence of these structures represents a potential technosignature that might be hiding in large astronomical surveys, and this thesis revolves around exploring such a premise. First, we devote our search to assessing upper limits on the prevalence of Dyson spheres in the Milky Way by analyzing combined optical and mid-infrared photometric data. These upper limits are presented on the fraction of stars that may potentially host Dyson spheres and are model-dependent. We find robust limits of 1 over 100,000 stars for 300 K Dyson spheres at a 90% completion level within 100 pc. After that, we develop a pipeline especially tailored to identify potential Dyson sphere candidates in a sample of five million objects with available optical, near, and mid-infrared photometric data. This pipeline yields seven M dwarfs exhibiting anomalous infrared excess that deserve further analysis. Finally, we present an analysis of photometric and, in some cases, spectroscopic data on these seven objects, plus three additional sources sharing similar properties. The stellar parameters, derived from calibrated empirical relationships for M dwarfs, reveal no irregularities compared to the typical M dwarf population. While the infrared properties of our targets resemble, in some cases, those of young stars, spectroscopic data show no signs of youth usually observed for such objects. We still lack a clear explanation for the infrared excess of these stars, but we acknowledge that future follow-up observations could probe scenarios in which the infrared excess is due to circumstellar dust emission.
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