Model of the Search For Extraterrestrial Intelligence with Coronagraphic Imaging

TL;DR

This paper models the detection limits of GPI and WFIRST coronagraphs for extraterrestrial laser signals, demonstrating their potential to identify signals from nearby stars like τ Ceti within habitable zones.

Contribution

It introduces a method to estimate the detectability of extraterrestrial laser signals using current and future coronagraphic telescopes, based on archival and simulated data.

Findings

GPI can detect a 24 kW laser from τ Ceti outside its habitable zone.

WFIRST can detect a 7.3 W laser within τ Ceti's habitable zone.

Detection limits depend on laser power, distance, and instrument sensitivity.

Abstract

We present modeled detection limits of the Gemini Planet Imager (GPI) and the Wide-Field Infrared Space Telescope (WFIRST) to an optical and infrared laser which could be used by an extraterrestrial civilization to signal their presence. GPI and WFIRST could utilize a coronagraph to search for extraterrestrial intelligence (SETI) in the present and future. We use archival data for GPI stars and simulated WFIRST observations to find the detectable flux ratio of a laser signal to residual scattered starlight around the target star. This flux ratio is then converted to detectable power as a function of distance from the parent star. For GPI, we assume a monochromatic laser wavelength of 1.55 $\mu$m, and a wavelength of 575 nm for WFIRST. We assume the lasers are projected through a 10-m aperture, and that the intensity of the laser beam follows a Gaussian profile. Our analysis is performed on 6 stars with spectral types later than F within 20 pc (with an emphasis on solar analogs at different distances). The most notable result is the detection limit for $\tau$ Ceti, a G5V star with four known exoplanets, two of those within the habitable zone (HZ). The result shows that a 24 kW laser is detectable from $\tau$ Ceti from outside of the HZ with GPI and a 7.3 W laser is detectable from within $\tau$ Ceti's HZ by WFIRST.