Abstract
Abstract This paper examines the ability to produce a laser beam detectable to a cursory survey (SNR 0.1% with a 1 m receive telescope) by an extraterrestrial intelligence using proven or near-term technology (megawatt-class lasers, telescopes tens of meters in size). We find that such lasers can produce a signal at ranges of less than 20,000 lt-yr, with a broad enough beam to overcome uncertainties in nearby exoplanet orbits (e.g., Prox Cen b) or encompass entire habitable zones of more distant systems (e.g., TRAPPIST-1). While the probability of closing a handshake with even a nearby extraterrestrial intelligence is low with current survey methodologies, advances in full-sky surveys for SETI and other purposes may reduce the mean-time-to-handshake to decades or centuries, after which these laser systems may close links at data rates of kbps–Mpbs. The next major gap to address for searching for extraterrestrial lasers is in expanding spectral searches into the infrared, where most terrestrial communication and high-power lasers are manufactured.
Highlights
There is interest in building gargantuan lasers to accelerate small spacecraft at other stars
No continuous-wave laser has ever been built to that scale. This leaves the open question: could lasers and telescopes that exist today or in the decade be used to signal a nearby extraterrestrial intelligence? Could we produce a detectable laser beam and direct it toward a nearby system, with a beamwidth that is larger than our uncertainty in the positions of those planets? What data rates are achievable once contact is made?
An extremely narrow beam may only be as wide as a planet, even after traveling interstellar distances
Summary
There is interest in building gargantuan lasers to accelerate small spacecraft at other stars. A 100 GW “DE-STAR 4” laser operating at a wavelength of 1064 nm, as proposed by Lubin (2016a), could be detectable at interstellar and even intergalactic distances by a civilization with our technology (Lubin 2016b). No continuous-wave laser has ever been built to that scale. This leaves the open question: could lasers and telescopes that exist today or in the decade be used to signal a nearby (hypothetical) extraterrestrial intelligence? Could we produce a detectable laser beam and direct it toward a nearby system, with a beamwidth that is larger than our uncertainty in the positions of those planets? This leaves the open question: could lasers and telescopes that exist today or in the decade be used to signal a nearby (hypothetical) extraterrestrial intelligence? Could we produce a detectable laser beam and direct it toward a nearby system, with a beamwidth that is larger than our uncertainty in the positions of those planets? What data rates are achievable once contact is made?
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