SETI with Gaia: The observational signatures of nearly complete Dyson spheres (1804.08351v2)

Abstract: A star enshrouded in a Dyson sphere with high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson-sphere searches that are complementary to searches based on waste-heat signatures at infrared wavelengths. A limited search of this type is also possible at the current time, by combining Gaia parallax distances with spectrophotometric distances from ground-based surveys. Here, we discuss the merits and shortcomings of this technique and carry out a limited search for Dyson-sphere candidates in the sample of stars common to Gaia Data Release 1 and RAVE Data Release 5. We find that a small fraction of stars indeed display distance discrepancies of the type expected for nearly complete Dyson spheres. To shed light on the properties of objects in this outlier population, we present follow-up high-resolution spectroscopy for one of these stars, the late F-type dwarf TYC 6111-1162-1. The spectrophotometric distance of this object is about twice that derived from its Gaia parallax, and there is no detectable infrared excess. While our analysis largely confirms the stellar parameters and the spectrophotometric distance inferred by RAVE, a plausible explanation for the discrepant distance estimates of this object is that the astrometric solution has been compromised by an unseen binary companion, possibly a rather massive white dwarf ($\approx 1\ M_\odot$). This scenario can be further tested through upcoming Gaia data releases.

• The paper introduces a technique comparing Gaia parallax and spectrophotometric distances to identify potential Dyson sphere signatures.
• It finds high covering fraction outliers that may mimic Dyson spheres, though further analysis indicates binary star effects and lack of infrared excess as confounding factors.
• Future Gaia data releases are expected to reduce false positives and refine the search for genuine astroengineering structures in stellar datasets.

Analyzing Dyson Sphere Indicators with Gaia Data

The paper entitled "SETI with Gaia: The observational signatures of nearly complete Dyson spheres" by Erik Zackrisson et al. contributes a novel observational methodology to the SETI investigation framework, leveraging data from the Gaia mission. Specifically, it explores the potential of identifying Dyson spheres - conjectural megastructures encompassing stars to harness energy - through parallax and spectrophotometric distance discrepancies.

The authors premise this paper on the concept that a Dyson sphere with a high covering fraction would alter typical stellar signatures. Such a structure would cause affected stars to appear optically subluminous relative to their spectrophotometric estimate due to the significant quenching of visible and near-infrared brightness. Yet, Gaia’s parallax measurements would remain precise, enabling a calculated mismatch between Gaia’s trigonometric distances and those predicted from ground-based surveys.

Noteworthy from the paper are several high-$f_\mathrm{cov}$ outlier stars within the data cross-matched from Gaia Data Release 1 (DR1) and RAVE DR5 catalogs. These outliers exhibit distance discrepancies that could mimic the characteristics of nearly complete Dyson spheres. However, upon further scrutiny, one of these stars - TYC 6111-1162-1 - appears to showcase an inconsistency attributed to binary star dynamics rather than extraterrestrial architectures. A lack of infrared excess detected by WISE further negates the possibility of a Dyson sphere, as such a structure would typically exhibit waste heat emission resulting in a mid-infrared signature.

What surfaces from this segment of research is a cautionary approach: the primary limiting factor in identifying authentic Dyson sphere signatures remains the potential overlap with naturally occurring stellar phenomena, such as unseen binary companions affecting parallax readings or non-thermally radiant structures influencing spectral data.

This framework's future strengthening hinges on upcoming Gaia data releases. Gaia's DR3 is projected to vastly increase the number of stars with reliable spectrophotometric distances, potentially reducing false positive rates encountered in such analyses. As data quality improves, particularly through identifying binary systems more accurately, this method might discern true Dyson sphere candidates from merely statistical anomalies or artifacts of interstellar phenomena, such as grey dust obscuration.

From a broader theoretical perspective, the implications of this work are profound for both SETI and stellar astrophysics. The research offers a quantitative probe into the space of mega-engineering and a rigorous test of stellar data models. As the observational horizon expands with increased Gaia data, and with further refinement in data interoperability among astronomical surveys, the framework presented could have far-reaching implications in extending humanity's search for extraterrestrial intelligences, should they exist, engaged in large-scale astroengineering.