Stellar Gravitational Lens Engineering for Interstellar Communication and Artifact SETI

Abstract

Several recent works have proposed a “stellar relay” transmission system in which a spacecraft at the focus of a star’s gravitational lens achieves dramatic boosts in the gain of an outgoing or incoming interstellar transmission. We examine some of the engineering requirements of a stellar relay system, evaluate the long-term sustainability of a gravitational relay, and describe the perturbations and drifts that must be actively countered to maintain a relay-star-target alignment. The major perturbations on a relay-Sun-target alignment are the inwards gravity of the Sun and the reflex motion of the Sun imparted by the planets. These ∼m s−1 yr−1 accelerations can be countered with modern propulsion systems over century-long timescales. This examination is also relevant for telescope designs aiming to use the Sun as a focusing element. We additionally examine prospects for an artifact SETI search to observe stellar relays placed around the Sun by an extraterrestrial intelligence and suggest certain nearby stars that are relatively unperturbed by planetary systems as favorable nodes for a stellar relay communications system.

A Search for Radio Technosignatures at the Solar Gravitational Lens Targeting Alpha Centauri

“…Hippke (2020b) also notes that, in this proposed configuration, separate exploration probes would be required in order to study the inner solar system. Kerby & Wright (2021) explore the engineering requirements and sustainability for an SGL relay to remain in proper position, finding that such technology is feasible and noting that another observable property of such probes may be the by-products of station-keeping propulsion. They also argued that single stars (i.e., those with minimal gravitational perturbations from companions) were the best hosts for such probes because their station-keeping costs were smallest.…”

“…Although α Cen belongs to our nearest neighboring star system, it may not be the best star to study in the SGL network context. Kerby & Wright (2021) found that close binary star systems are unsuitable for stellar gravitational lens relays due to the high delta-v cost required to maintain alignment. Kerby & Wright 2021 instead suggest that the best candidate stars for hosting relay systems are without close companions, without large gas giant planets, relatively low in mass, and not spinning rapidly enough to deviate from sphericity.…”

SETI in 2021

“…Hippke (2021a) set forth the third work in the "Interstellar communication network" series, describing how to locate candidate sky positions for nodes in the solar system. Kerby & Wright (2021) examined the engineering requirements of such a stellar relay system, considering how stellar and planetary system architectures affect the ability to maintain relay-star-target alignment. Gertz (2021a) elaborated on how a Galactic communication network may operate and concluded that the search for such probes may be more fruitful than the search for electromagnetic signals targeted toward Earth.…”

Search for an Alien Message to a Nearby Star

“…Based on this hypothesis, G14 proposed a novel search for extraterrestrial intelligence (SETI; Tarter 2001) strategy consisting in the intense multispectral monitoring of the focal regions of the nearest stars, with the hope of catching a communication leakage from the FICDs. This strategy has been explored further by subsequent studies (Gertz 2018(Gertz , 2021Hippke 2020aHippke , 2020bHippke , 2021Kerby & Wright 2021;Marcy et al 2022). Notably, Kerby & Wright (2021) examined the engineering requirements of the GL-based interstellar communication method, showing that modern propulsion systems should enable FICDs to maintain their interstellar communication link over century-long timescales provided that their host stars are relatively unperturbed (e.g., by a stellar companion).…”

“…This strategy has been explored further by subsequent studies (Gertz 2018(Gertz , 2021Hippke 2020aHippke , 2020bHippke , 2021Kerby & Wright 2021;Marcy et al 2022). Notably, Kerby & Wright (2021) examined the engineering requirements of the GL-based interstellar communication method, showing that modern propulsion systems should enable FICDs to maintain their interstellar communication link over century-long timescales provided that their host stars are relatively unperturbed (e.g., by a stellar companion).…”