![Blackbody spectra derived from the 𝑇eff of the Dyson sphere candidates A to J throughout the wavelength range of 10 to 1000 microns together with the detection thresholds of telescopes Akari (Murakami et al. 2007), IRAS (Neugebauer et al. 1984), the ALMA 12∼m array6 and JWST/MIRI. In the case of JWST, both broadband imaging and spectroscopic limits (based on the LRS Slit or MRS7observations) are shown. In the case of JWST and ALMA, all limits refer to 5𝜎 confidence in 1 hour exposure time (where exposure times refer to observations per filter in the case of imaging; per band in the case of ALMA spectroscopy; per channel in the case of JWST/MIRI MRS spectroscopy and for the entire plotted wavelength range in the case of JWST/LRS spectroscopy). As can be seen, all candidates are detectable throughout some part of the wavelength coverage of JWST. The inset shows a zoom-in on the part of the spectral energy distribution that may be detectable with ALMA for four of the candidates (A, G, I and J). -- [astro-ph.SR]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Project-Hephaistos-1.png?fit=1200%2C676&ssl=1)
[astro-ph.SR] The infrared-flux excess of stars harbouring Dyson spheres represent one potential technosignature of extraterrestrial intelligence.
In a previous Project Hephaistos paper, we highlighted seven M dwarfs within 300 pc with unusual infrared properties that seem to resemble those expected for Dyson spheres.
In the present study, we present an analysis of photometric and, in some cases, spectroscopic data on these seven objects, plus three additional objects with similar properties, to further constrain their nature.
The stellar parameters, derived from calibrated empirical relationships for M dwarfs, reveal no irregularities with respect to the overall M-dwarf population of main-sequence stars. While the infrared properties of our targets resemble those of circumstellar disks in a transitional state, the objects with spectroscopic data show no signs of youth usually associated with such objects.
One of our spectroscopic targets does exhibit weak Hα emission, but this is more likely attributed to stellar activity than to the gaseous accretion disk expected for a young star.
After this analysis, we still find no clear explanation for the infrared excess of these stars, but note that observations with the JWST and/or the Atacama Large Millimeter/submillimeter Array would be able to probe scenarios in which the infrared excess is due to circumstellar dust emission or an infrared-bright background source that remains undetected at shorter wavelengths.
For two of our stars, JWST observations have recently revealed superpositions with very red background galaxies.
Andreas J. Korn, Matías Suazo, Erik Zackrisson, Pía Cortés-Zuleta, Adam D. Rains, Armin Nabizadeh
Comments: 11 pages, 9 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2607.25701 [astro-ph.SR] (or arXiv:2607.25701v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2607.25701
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Submission history
From: Andreas Korn
[v1] Tue, 28 Jul 2026 13:23:18 UTC (2,362 KB)
https://arxiv.org/abs/2607.25701
Astrobiology, SETI, Technosignature,
