Technosignature
[1] Various types of technosignatures, such as radiation leakage from megascale astroengineering installations such as Dyson spheres, the light from an extraterrestrial ecumenopolis, or Shkadov thrusters with the power to alter the orbits of stars around the Galactic Center, may be detectable with hypertelescopes.
[11] Shkadov thrusters, with the hypothetical ability to change the orbital paths of stars in order to avoid various dangers to life such as cold molecular clouds or cometary impacts, would also be detectable in a similar fashion to the transiting extrasolar planets searched by Kepler.
Unlike planets, though, the thrusters would appear to abruptly stop over the surface of a star rather than crossing it completely, revealing their technological origin.
[15] Other characteristics proposed as potential technosignatures (or starting points for detection of clearer signatures) include peculiar orbital periods such as arranging planets in prime number patterns.
[4] For example, NASA's 2012 Black Marble experiment showed that significant stable light and heat sources on Earth, such as chronic wildfires in arid Western Australia, originate from uninhabited areas and are naturally occurring.
Work by astronomer Thomas Beatty has shown that the spectrally concentrated emission from sodium street lights would be distinguishable from natural sources using proposed next generation space telescopes.
[35][36] For example, atmospheric emissions from human technology use on Earth, including nitrogen dioxide and chlorofluorocarbons, are detectable from space.
[42] However, there remains a possibility of mis-detection; for example, the atmosphere of Titan has detectable signatures of complex chemicals that are similar to what on Earth are industrial pollutants, though not the byproduct of civilisation.
[43] Some SETI scientists have proposed searching for artificial atmospheres created by planetary engineering to produce habitable environments for colonisation by an ETI.
[51] It has been suggested that once extraterrestrials arrive "at a new home, such life will almost certainly create technosignatures (because it used technology to get there), and some fraction of them may also eventually give rise to a new biosphere".
[53][additional citation(s) needed] See also: DNA digital data storage Low- or high-albedo installations such as solar panels may also be detectable, albeit distinguishing artificial megastructures from high- and low-albedo natural environments (e.g., bright ice caps) may make it unfeasible.
[26] One of the first attempts to search for Dyson Spheres was made by Vyacheslav Slysh from the Russian Space Research Institute in Moscow in 1985 using data from the Infrared Astronomical Satellite (IRAS).
[55] Another search for technosignatures, c. 2001, involved an analysis of data from the Compton Gamma Ray Observatory for traces of anti-matter, which, besides one "intriguing spectrum probably not related to SETI", came up empty.
[60] In a 2005 paper, Luc Arnold proposed a means of detecting planetary-sized artifacts from their distinctive transit light curve signature.
He showed that such technosignature was within the reach of space missions aimed at detecting exoplanets by the transit method, as were Corot or Kepler projects at that time.
[62][63][64] In 2012, a trio of astronomers led by Jason Wright started a two-year search for Dyson Spheres, aided by grants from the Templeton Foundation.
[81][82] In 2022, scientists provided an overview of the capabilities of ongoing, recent, past, planned and proposed missions and observatories for detecting various alien technosignatures.
