Technosignature

Illustration of various types of technosignatures.

Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology.<ref name="tarter-2018" /><ref name="UT-2018" /> Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not.<ref name=tarter-2018 /><ref name="WP-20201231">Frank, Adam (31 December 2020). "A new frontier is opening in the search for extraterrestrial life - The reason we haven't found life elsewhere in the universe is simple: We haven't really looked until now". The Washington Post. Retrieved 1 January 2021.</ref> Some authors prefer to exclude radio transmissions from the definition,<ref name=almar-2011>Almár, Iván (2011). "SETI and astrobiology: The Rio Scale and the London Scale". Acta Astronautica. 69 (9–10): 899–904. Bibcode:2011AcAau..69..899A. doi:10.1016/j.actaastro.2011.05.036.(subscription required)</ref> but such restrictive usage is not widespread. Jill Tarter has proposed that the search for extraterrestrial intelligence (SETI) be renamed "the search for technosignatures".<ref name="tarter-2018" /> 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. Some examples of technosignatures are described in Paul Davies's 2010 book The Eerie Silence, although the terms "technosignature" and "technomarker" do not appear in the book.

In February 2023, astronomers reported, after scanning 820 stars, the detection of 8 possible technosignatures for follow-up studies.<ref name="NA-20221130">Ma, Peter Xiangyuan; et al. (30 November 2022). "A deep-learning search for technosignatures of 820 nearby stars" (PDF). Nature Astronomy. Retrieved 11 February 2023.</ref>

Astroengineering projects

A Dyson sphere, one of the best-known speculative technologies that may generate a technosignature

A Dyson sphere, constructed by life forms dwelling in proximity to a Sun-like star, would cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Freeman Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his 1960 paper on the subject.<ref name="search">Freemann J. Dyson (1960). "Search for Artificial Stellar Sources of Infra-Red Radiation". Science. 131 (3414): 1667–1668. Bibcode:1960Sci...131.1667D. doi:10.1126/science.131.3414.1667. PMID 17780673. S2CID 3195432.</ref> SETI has adopted these assumptions in its search, looking for such "infrared heavy" spectra from solar analogs. Since 2005, Fermilab has conducted an ongoing survey for such spectra, analyzing data from the Infrared Astronomical Satellite.<ref name=carrigan>Carrigan, Dick (2006). "Fermilab Dyson Sphere search program". Archived from the original on 2006-03-06. Retrieved 2006-03-02.</ref><ref>Shostak, Seth (Spring 2009). "When Will We Find the Extraterrestrials?" (PDF). Engineering & Science. 72 (1): 12–21. ISSN 0013-7812. Archived from the original (PDF) on 2015-04-15.</ref>

Identifying one of the many infra-red sources as a Dyson sphere would require improved techniques for discriminating between a Dyson sphere and natural sources.<ref>Carrigan, Richard; Dyson, Freeman J. (15 May 2009). "Dyson sphere at Scholarpedia". Scholarpedia. Scholarpedia.org. 4 (5): 6647. doi:10.4249/scholarpedia.6647.</ref> Fermilab discovered 17 "ambiguous" candidates, of which four have been named "amusing but still questionable".<ref name="Carrigan 2012">Carrigan, D. (2012). "Fermilab Dyson Sphere search program". Archived from the original on 2006-03-06. Retrieved 2012-01-15.</ref> Other searches also resulted in several candidates, which remain unconfirmed.<ref name=carrigan /> In October 2012, astronomer Geoff Marcy, one of the pioneers of the search for extrasolar planets, was given a research grant to search data from the Kepler telescope, with the aim of detecting possible signs of Dyson spheres.<ref>Sanders, Robert (5 October 2012). "Grants help scientists explore boundary between science & science fiction". Newscenter.berkeley.edu. Retrieved 2013-07-10.</ref>

Orbital paths, transit signatures, stellar activity and star-system composition

See also: Moving Earth and § Extraterrestrial artifacts, influence and spacecraft

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.<ref name=Villard2013>Villard, Ray (2013). "Alien 'Star Engine' Detectable in Exoplanet Data?". Discovery News. Archived from the original on 2013-06-28. Retrieved 2013-07-08.</ref> In addition, evidence of targeted extrasolar asteroid mining may also reveal extraterrestrial intelligence (ETI).<ref>Duncan Forgan; Martin Elvis (2011). "Extrasolar Asteroid Mining as Forensic Evidence for Extraterrestrial Intelligence". International Journal of Astrobiology. 10 (4): 307–313. arXiv:1103.5369. Bibcode:2011IJAsB..10..307F. doi:10.1017/S1473550411000127. S2CID 119111392.</ref> Furthermore, it has been suggested that information could be hidden within the transit signatures of other planets.<ref>Kipping, David (April 19, 2016). "Here's how we could hide Earth from aliens if we had to". Washington Post. Retrieved 22 November 2021.</ref> Advanced civilizations could "cloak their presence, or deliberately broadcast it, through controlled laser emission".<ref>Kipping, David M.; Teachey, Alex (21 June 2016). "A cloaking device for transiting planets". Monthly Notices of the Royal Astronomical Society. 459 (2): 1233–1241. arXiv:1603.08928. doi:10.1093/mnras/stw672.</ref> 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.<ref>Davenport, James R. A. (9 July 2019). "SETI in the Spatio-Temporal Survey Domain". arXiv:1907.04443 [astro-ph.IM].</ref><ref>Clement, Matthew S.; Raymond, Sean N.; Veras, Dimitri; Kipping, David (23 May 2022). "Mathematical encoding within multi-resonant planetary systems as SETI beacons". Monthly Notices of the Royal Astronomical Society. 513 (4): 4945–4950. arXiv:2204.14259. doi:10.1093/mnras/stac1234.</ref><ref>O'Callaghan, Jonathan (9 May 2022). "Aliens could say hello by arranging planets in prime number pattern". New Scientist. Retrieved 3 August 2022.</ref> Coronal and chromospheric activity on stars might be altered.<ref>Scharf, Caleb A. (March 7, 2018). "The Technosignature Challenge". Scientific American Blog Network. Retrieved 3 August 2022.</ref> Extraterrestrial civilizations may use free-floating planets (rogue planets) for interstellar transportation with a number of proposed possible technosignatures.<ref>Romanovskaya, Irina K. (June 2022). "Migrating extraterrestrial civilizations and interstellar colonization: implications for SETI and SETA". International Journal of Astrobiology. 21 (3): 163–187. Bibcode:2022IJAsB..21..163R. doi:10.1017/S1473550422000143. ISSN 1473-5504.</ref>

Communication networks

See also: Search for extraterrestrial intelligence § Quantum communications, and Ufology

A study suggests that if ETs exist, they may have established communications network(s) and may already have probes in the solar system whose communication may be detectable.<ref>Gillon, Michael; Burdanov, Artem; Wright, Jason T. (2022). "Search for an Alien Message to a Nearby Star". The Astronomical Journal. 164 (5): 221. arXiv:2111.05334. Bibcode:2022AJ....164..221G. doi:10.3847/1538-3881/ac9610. S2CID 253182278.

• News article: Williams, Matt. "If alien probes are already in the solar system, maybe we could detect them calling home". Universe Today.</ref> Studies by John Gertz suggest flyby (scout)<ref>Gertz, John (8 June 2021). "Oumuamua and Scout ET Probes". arXiv:1904.04914 [physics.pop-ph].</ref> probes might intermittently surveil nascent solar systems and permanent probes would communicate with a home base, potentially using triggers and conditions such as detection of electromagnetic leakage or biosignatures.<ref>Gertz, John. "Maybe the Aliens Really Are Here". Scientific American. Retrieved 3 August 2022.</ref> They also suggest several strategies to detecting local ET probes<ref>Gertz, John (4 December 2020). "Strategies for the Detection of ET Probes Within Our Own Solar System". Journal of the British Interplanetary Society. 74 (2): 47. arXiv:2011.12446. Bibcode:2021JBIS...74...47G.</ref> such as detecting emitted optical messages.<ref>Gillon, Michael; Burdanov, Artem; Wright, Jason T. (2022). "Search for an Alien Message to a Nearby Star". The Astronomical Journal. 164 (5): 221. arXiv:2111.05334. Bibcode:2022AJ....164..221G. doi:10.3847/1538-3881/ac9610. S2CID 253182278.</ref> He also finds that due to interstellar networks of communications nodes, the search for deliberate interstellar signals – as is common in SETI<ref name="10.3847/1538-3881/ab2df3">Berdyugina, S. V.; Kuhn, J. R. (25 November 2019). "Surface Imaging of Proxima b and Other Exoplanets: Albedo Maps, Biosignatures, and Technosignatures". The Astronomical Journal. 158 (6): 246. Bibcode:2019AJ....158..246B. doi:10.3847/1538-3881/ab2df3. ISSN 1538-3881. S2CID 213585876.</ref> – may be futile.<ref>Gertz, John (21 October 2021). "The Search for Deliberate Interstellar SETI Signals May Be Futile". Journal of the British Interplanetary Society. 74 (11): 414. arXiv:2110.11502. Bibcode:2021JBIS...74..414G.</ref> The architecture may consist of nodes separated by sub-light-year distances and strung out between neighboring stars.<ref>Gertz, John; Marcy, Geoffrey (27 April 2022). "Engineering an Interstellar Communications Network by Deploying Relay Probes". arXiv:2204.08296 [physics.pop-ph].</ref> It may also contain pulsars as beacons<ref>LaViolette, Paul A. (1999). "Evidence that Radio Pulsars may be Artificial Beacons of ETI Origin".</ref> or nodes whose beams are modulated by mechanisms that could be searched for.<ref>Haliki, Emir (October 2019). "Broadcast network model of pulsars as beacons of extraterrestrial civilizations". International Journal of Astrobiology. 18 (5): 455–462. Bibcode:2019IJAsB..18..455H. doi:10.1017/S1473550418000459. ISSN 1473-5504. S2CID 126214354.</ref> Moreover, a study suggests prior searches wouldn't have detected cost-effective electromagnetic signal beacons.<ref>"Stingy aliens may call us on cheap rates only". New Scientist. Retrieved 3 August 2022.</ref>

Planetary analysis

Artificial heat and light

Lights from cities and infrastructure on Earth at night from space

Various astronomers, including Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and Edwin L. Turner of Princeton University have proposed that artificial light from extraterrestrial planets, such as that originating from cities, industries, and transport networks, could be detected and signal the presence of an advanced civilization. Such approaches, though, make the assumption that the radiant energy generated by civilization would be relatively clustered and can therefore be detected easily.<ref>"SETI search urged to look for city lights". UPI.com. 2011-11-03. Retrieved 2013-07-10.</ref><ref>Extrasolar Planets: Formation, Detection and Dynamics Rudolf Dvorak, page 14 John Wiley & Sons, 2007</ref>

Light and heat detected from planets must be distinguished from natural sources to conclusively prove the existence of intelligent life on a planet.<ref name=almar-2011 /> 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.<ref>"Wildfires Light Up Western Australia". Nasa.gov. 2012-12-07. Retrieved 2013-07-10.</ref> The proposed LUVOIR A may be able to detect city lights twelve times those of Earth on Proxima b in 300 hours.<ref>Beatty, Thomas G. (6 May 2022). "The Detectability of Nightside City Lights on Exoplanets". Monthly Notices of the Royal Astronomical Society. 513 (2): 2652–2662. arXiv:2105.09990. doi:10.1093/mnras/stac469.</ref>

Atmospheric analysis

Artist's illustration of an advanced ET civilization with industrial pollution<ref>Steigerwald, Bill (22 January 2021). "Find an Extraterrestrial Civilization Using Its Pollution". NASA. Retrieved 4 April 2021.</ref>

Atmospheric analysis of planetary atmospheres, as is already done on various Solar System bodies and in a rudimentary fashion on several hot Jupiter extrasolar planets, may reveal the presence of chemicals produced by technological civilizations.<ref name="NYT-20220915">Gertner, Jon (15 September 2022). "The Search for Intelligent Life Is About to Get a Lot More Interesting - There are an estimated 100 billion galaxies in the universe, home to an unimaginable abundance of planets. And now there are new ways to spot signs of life on them". The New York Times. Retrieved 15 September 2022.</ref><ref name=choi-2012>Choi, Charles Q. (2012-11-26). "Alien Hairspray May Help Us Find E.T." Space.com. Retrieved 2013-07-10.</ref> For example, atmospheric emissions from human technology use on Earth, including nitrogen dioxide and chlorofluorocarbons, are detectable from space.<ref>"Satellite sniffs out chemical traces of atmospheric pollution / Observing the Earth / Our Activities / ESA". Esa.int. 2000-12-18. Retrieved 2013-07-10.</ref> Artificial air pollution may therefore be detectable on extrasolar planets and on Earth via "atmospheric SETI" – including NO₂ pollution levels and with telescopic technology close to today.<ref>"Pollution on other planets could help us find aliens, Nasa says". The Independent. 12 February 2021. Archived from the original on 2022-05-26. Retrieved 6 March 2021.</ref><ref>Herbst, Meghan (March 4, 2021). "Can Alien Smog Lead Us to Extraterrestrial Civilizations?". Wired. Retrieved 6 March 2021.</ref><ref>Kopparapu, Ravi; Arney, Giada; Haqq-Misra, Jacob; Lustig-Yaeger, Jacob; Villanueva, Geronimo (22 February 2021). "Nitrogen Dioxide Pollution as a Signature of Extraterrestrial Technology". The Astrophysical Journal. 908 (2): 164. arXiv:2102.05027. Bibcode:2021ApJ...908..164K. doi:10.3847/1538-4357/abd7f7. S2CID 231855390.</ref><ref>Haqq-Misra, Jacob; Kopparapu, Ravi; Fauchez, Thomas J.; Frank, Adam; Wright, Jason T.; Lingam1, Manasvi (1 March 2022). "Detectability of Chlorofluorocarbons in the Atmospheres of Habitable M-dwarf Planets". The Planetary Science Journal. 3 (3): 60. arXiv:2202.05858. Bibcode:2022PSJ.....3...60H. doi:10.3847/PSJ/ac5404. S2CID 246824041.{{cite journal}}: CS1 maint: numeric names: authors list (link)</ref> Such technosignatures may consist not of the detection of the level of one specific chemical but simultaneous detections of levels of multiple specific chemicals in atmospheres.<ref>Haqq-Misra, Jacob; Fauchez, Thomas J.; Schwieterman, Edward W.; Kopparapu, Ravi (1 April 2022). "Disruption of a Planetary Nitrogen Cycle as Evidence of Extraterrestrial Agriculture". The Astrophysical Journal Letters. 929 (2): L28. arXiv:2204.05360. Bibcode:2022ApJ...929L..28H. doi:10.3847/2041-8213/ac65ff. S2CID 248119062.</ref>

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.<ref>"Haze on Saturn's Moon Titan Is Similar to Earth's Pollution". Space.com. June 7, 2013. Retrieved 2013-07-10.</ref> Some SETI scientists have proposed searching for artificial atmospheres created by planetary engineering to produce habitable environments for colonisation by an ETI.<ref name=choi-2012 />

Extraterrestrial artifacts, influence and spacecraft

See also: Ufology § Research

Spacecraft

See also: Fast radio burst

The IKAROS light sail of 2010

Interstellar spacecraft may be detectable from hundreds to thousands of light-years away through various forms of radiation, such as the photons emitted by an antimatter rocket or cyclotron radiation from the interaction of a magnetic sail with the interstellar medium. Such a signal would be easily distinguishable from a natural signal and could hence firmly establish the existence of extraterrestrial life, were it to be detected.<ref>Zubrin, Robert (1995). "Detection of Extraterrestrial Civilizations via the Spectral Signature of Advanced Interstellar Spacecraft". In Shostak, Seth (ed.). Astronomical Society of the Pacific Conference Series. Progress in the Search for Extraterrestrial Life. Astronomical Society of the Pacific. pp. 487–496. Bibcode:1995ASPC...74..487Z.</ref> In addition, smaller Bracewell probes within the Solar System itself may also be detectable by means of optical or radio searches.<ref name=freitas-1983>Freitas, Robert (November 1983). "The Case for Interstellar Probes". Journal of the British Interplanetary Society. 36: 490–495. Bibcode:1983JBIS...36..490F.</ref><ref name=tough-1998-2>Tough, Allen (1998). "Small Smart Interstellar Probes" (PDF). Journal of the British Interplanetary Society. 51: 167–174.</ref> Self-replicating spacecraft or their communications networks could potentially be detectable within our Solar system or in nearby star-based systems,<ref>Gillon, Michaël (February 2014). "A novel SETI strategy targeting the solar focal regions of the most nearby stars". Acta Astronautica. 94 (2): 629–633. arXiv:1309.7586. Bibcode:2014AcAau..94..629G. doi:10.1016/j.actaastro.2013.09.009. S2CID 53990678.</ref> if they are located there.<ref>Edwards, Lin (July 19, 2013). "Self-replicating alien probes could already be here". Phys.org. Retrieved 30 April 2021.</ref> Such technologies or their footprints could be in Earth's orbit, on the Moon or on the Earth.

Satellites

A less advanced technology, and one closer to humanity's current technological level, is the Clarke Exobelt proposed by Astrophysicist Hector Socas-Navarro of the Instituto de Astrofisica de Canarias.<ref>Dorminey, Bruce (February 24, 2018). "NASA's TESS Telescope May Spot Alien Geo-Satellites, Say Astronomers". Forbes. Retrieved 12 June 2018.</ref> This hypothetical belt would be formed by all the artificial satellites occupying geostationary/geosynchronous orbits around an exoplanet. From early simulations it appeared that a very dense satellite belt, requiring only a moderately more-advanced civilization than ours, would be detectable with existing technology in the light curves from transiting exoplanets,<ref>Hector Socas-Navarro (2018-02-21). "Possible Photometric Signatures of Moderately Advanced Civilizations: The Clarke Exobelt". The Astrophysical Journal. 855 (2): 110. arXiv:1802.07723. Bibcode:2018ApJ...855..110S. doi:10.3847/1538-4357/aaae66. S2CID 55234856.</ref> but subsequent analysis has questioned this result, suggesting that exobelts detectable by current and upcoming missions will be very rare.<ref>Shauna Sallmen; Eric J. Korpela; Kaisa Crawford-Taylor (2019-11-02). "Improved Analysis of Clarke Exobelt Detectability". The Astronomical Journal. 158 (6): 258. arXiv:1909.10061. Bibcode:2019AJ....158..258S. doi:10.3847/1538-3881/ab5300. S2CID 202719280.</ref>

Extraterrestrial influence or activity on Earth

See also: Directed panspermia § Signal in the genome, and Ufology § Phenomena linked to ufology

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".<ref>Wright, Jason T.; Haqq-Misra, Jacob; Frank, Adam; Kopparapu, Ravi; Lingam, Manasvi; Sheikh, Sofia Z. (1 March 2022). "The Case for Technosignatures: Why They May Be Abundant, Long-lived, Highly Detectable, and Unambiguous". The Astrophysical Journal Letters. 927 (2): L30. arXiv:2203.10899. Bibcode:2022ApJ...927L..30W. doi:10.3847/2041-8213/ac5824. ISSN 2041-8205. S2CID 247448627.</ref> Microorganism DNA may have been used for self-replicating messages.<ref>Ellery, Alex (2022). "Self-replicating probes are imminent – implications for SETI". International Journal of Astrobiology. 21 (4): 212–242. Bibcode:2022IJAsB..21..212E. doi:10.1017/S1473550422000234. ISSN 1473-5504. S2CID 250398136.</ref> See also: DNA digital data storage

On exoplanets

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.<ref name="10.3847/1538-3881/ab2df3"/>

Scientific projects searching for technosignatures

Major technosignatures as outlined in a 2021 scientific review.<ref name="10.1016/j.actaastro.2021.02.029"/>

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).<ref>Battersby, Stephen (3 April 2013). "Alien megaprojects: The hunt has begun". New Scientist. Retrieved 2019-06-02.</ref>

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.<ref name="harris-2001" />

In 2005, Fermilab had an ongoing survey for such spectra by analyzing data from IRAS.<ref>Carrigan, D. (2006). "Fermilab Dyson Sphere search program". Archived from the original on 2006-03-06. Retrieved 2006-03-02.</ref><ref>Shostak, Seth (Spring 2009). "When Will We Find the Extraterrestrials?" (PDF). Engineering & Science. 72 (1): 12–21. ISSN 0013-7812. Archived from the original (PDF) on 2015-04-15.</ref> Identifying one of the many infra-red sources as a Dyson Sphere would require improved techniques for discriminating between a Dyson Sphere and natural sources.<ref>Dyson sphere at Scholarpedia</ref> Fermilab discovered 17 potential "ambiguous" candidates of which four have been named "amusing but still questionable".<ref name="Carrigan 2012"/> Other searches also resulted in several candidates, which are, however, unconfirmed.<ref>Dick Carrigan (2010-12-16). "Dyson Sphere Searches". Home.fnal.gov. Retrieved 2012-06-12.</ref>

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.<ref>Arnold, Luc F. A. (July 2005). "Transit Light-Curve Signatures of Artificial Objects". The Astrophysical Journal. 627 (1): 534–539. arXiv:astro-ph/0503580. Bibcode:2005ApJ...627..534A. doi:10.1086/430437. S2CID 15396488.</ref> The principle of the detection remains applicable for future exoplanets missions.<ref>Transiting Exoplanet Survey Satellite TESS. NASA.</ref><ref>"CHEOPS CHaracterising ExOPlanet Satellite".</ref><ref>PLATO PLAnetary Transits and Oscillations of stars. ESA.</ref>

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.<ref name="UT-2013" />

In 2013, Geoff Marcy received funding to use data from the Kepler Telescope to search for Dyson Spheres and interstellar communication using lasers,<ref name="SMH-2013" /> and Lucianne Walkowicz received funding to detect artificial signatures in stellar photometry.<ref>"New Frontiers in Astronomy: The research grant winners | ScienceBlogs". Archived from the original on 2013-10-22.</ref>

Starting in 2016, astronomer Jean-Luc Margot of UCLA has been searching for technosignatures with large radio telescopes.<ref name="UT-2018" />

Vanishing stars

In 2016, it was proposed that vanishing stars are a plausible technosignature.<ref name="Villarroel et al 2016">Villarroel, Beatriz; Imaz, Inigo; Bergstedt, Josefine (6 September 2016). "Our sky now and then: searches for lost stars and impossible effects as probes of advanced extraterrestrial civilizations". The Astronomical Journal. 152 (3): 76. arXiv:1606.08992. Bibcode:2016AJ....152...76V. doi:10.3847/0004-6256/152/3/76. S2CID 118514910.</ref> A pilot project searching for vanishing stars was carried out, finding one candidate object. In 2019, the Vanishing & Appearing Sources during a Century of Observations (VASCO) project<ref>Villarroel, Beatriz; Soodla, Johan; Comerón, Sébastien; Mattsson, Lars; Pelckmans, Kristiaan; López-Corredoira, Martín; Krisciunas, Kevin; Guerras, Eduardo; Kochukhov, Oleg; Bergstedt, Josefine; Buelens, Bart; Bär, Rudolf E.; Cubo, Rubén; Enriquez, J. Emilio; Gupta, Alok C.; Imaz, Iñigo; Karlsson, Torgny; Prieto, M. Almudena; Shlyapnikov, Aleksey A.; de Souza, Rafael S.; Vavilova, Irina B.; Ward, Martin J. (12 December 2019). "The Vanishing and Appearing Sources during a Century of Observations Project. I. USNO Objects Missing in Modern Sky Surveys and Follow-up Observations of a "Missing Star"". The Astronomical Journal. 159 (1): 8. arXiv:1911.05068. doi:10.3847/1538-3881/ab570f. ISSN 1538-3881. S2CID 207863387.</ref> began more general searches for vanishing and appearing stars, and other astrophysical transients<ref name="Villarroel et al 2016"/> They identified 100 red transients of "most likely natural origin", while analyzing 15% of the image data. In 2020, the VASCO collaboration started up a citizen science project, vetting through images of many thousands of candidate objects.<ref>"Look to the sky and help researchers in a new citizen science project - Stockholm University".</ref> The citizen science project is carried out in close collaboration with schools and amateur associations mainly in African countries.<ref>Villarroel, Beatriz; Pelckmans, Kristiaan; Solano, Enrique; Laaksoharju, Mikael; Souza, Abel; Dom, Onyeuwaoma Nnaemeka; Laggoune, Khaoula; Mimouni, Jamal; Mattsson, Lars; Soodla, Johan; Castillo, Diego; Shultz, Matthew E.; Aworka, Rubby; Comerón, Sébastien; Geier, Stefan; Marcy, Geoffrey; Gupta, Alok C.; Bergstedt, Josefine; Bär, Rudolf E.; Buelens, Bart; Prieto, M. Almudena; Ramos-Almeida, Cristina; Wamalwa, Dismas Simiyu; Ward, Martin J. (2022). "Launching the VASCO Citizen Science Project". Universe. 8 (11): 561. arXiv:2009.10813. Bibcode:2022Univ....8..561V. doi:10.3390/universe8110561.</ref> The VASCO project has been referred to as "Perhaps the most general artefact search to date".<ref>Shostak, Seth (December 2020). "SETI: the argument for artefact searches". International Journal of Astrobiology. 19 (6): 456–461. Bibcode:2020IJAsB..19..456S. doi:10.1017/S1473550420000233. S2CID 225252511.</ref> In 2021, VASCO's principal investigator Beatriz Villarroel received a L'Oreal-Unesco prize in Sweden for the project.<ref>"Prize to promising astrophysicist - Stockholm University".</ref> In June 2021, the collaboration published the discovery of nine light sources seemingly appearing and vanishing simultaneously from archival plates taken in 1950.<ref>Villarroel, Beatriz; Marcy, Geoffrey W.; Geier, Stefan; Streblyanska, Alina; Solano, Enrique; Andruk, Vitaly N.; Shultz, Matthew E.; Gupta, Alok C.; Mattsson, Lars (17 June 2021). "Exploring nine simultaneously occurring transients on April 12th 1950". Scientific Reports. 11 (1): 12794. arXiv:2106.11780. Bibcode:2021NatSR..1112794V. doi:10.1038/s41598-021-92162-7. PMC 8211679. PMID 34140604.</ref> Villarroel's team also found three 16th magnitude stars which had vanished on plates exposed within one hour of each other on 19 July 1952.<ref>Solano, Enrique; Marcy, Geoffery; Villarroel, Beatriz; Geier, Stefan; Streblyanska, Alina; Lombardi, Gianluka; Rudolf, Bar; Androk, Vitaly (January 2024). "A bright triple transient that vanished within 50 min". Monthly Notices of the Royal Astronomical Society. 527 (3): 6312. arXiv:2310.09035. Bibcode:2024MNRAS.527.6312S. doi:10.1093/mnras/stad3422. Archived from the original on 15 January 2024. Retrieved 15 January 2024 – via academic.oup.</ref>

Organization of novel projects

Methods and ancillary benefits of the search for various technosignatures.<ref name="10.1016/j.actaastro.2021.02.029"/>

In June 2020, NASA was awarded their first SETI-specific grant in three decades. The grant funds the first NASA-funded search for technosignatures from advanced extraterrestrial civilizations other than radio waves, including the creation and population of an online technosignature library.<ref>Irving, Michael (23 June 2020). "NASA funds SETI study to scan exoplanets for alien "technosignatures"". New Atlas. Retrieved 5 July 2020.</ref><ref>Rice, Doyle (June 20, 2020). "Scientists are searching the universe for signs of alien civilizations: 'Now we know where to look'". USA TODAY. Retrieved 5 July 2020.</ref><ref name="NASA-technosignatures">University of Rochester (June 19, 2020). "Does intelligent life exist on other planets? Technosignatures may hold new clues". Phys.org. Retrieved 5 July 2020.</ref> A 2021 scientific review produced by the i.a. NASA-sponsored online workshop TechnoClimes 2020 classified possible optimal mission concepts for the search of technosignatures. It evaluates signatures based on a metric about the distance of humanity to the capacity of developing the signature's required technology – a comparison to contemporary human technology footprints, associated methods of detection and ancillary benefits of their search for other astronomy. The study's conclusions include a robust rationale for organizing missions for searching artifacts – including probes – within the Solar system.<ref>Carter, Jamie (March 22, 2021). "Revealed: Why We Should Look For Ancient Alien Spacecraft On The Moon, Mars And Mercury According To NASA Scientists". Forbes. Retrieved 17 April 2021.</ref><ref name="10.1016/j.actaastro.2021.02.029">Socas-Navarro, Hector; Haqq-Misra, Jacob; Wright, Jason T.; Kopparapu, Ravi; Benford, James; Davis, Ross; TechnoClimes 2020 workshop participants (1 May 2021). "Concepts for future missions to search for technosignatures". Acta Astronautica. 182: 446–453. arXiv:2103.01536. Bibcode:2021AcAau.182..446S. doi:10.1016/j.actaastro.2021.02.029. ISSN 0094-5765. S2CID 232092198. Retrieved 17 April 2021.{{cite journal}}: CS1 maint: numeric names: authors list (link) Available under CC BY 4.0 on arXiv.</ref>

In 2021, astronomers proposed a sequence of "verification checks for narrowband technosignature signals" after concluding that technosignature candidate BLC1 could be the result of a form of local radiofrequency interference.<ref>Sheikh, Sofia Z.; Smith, Shane; Price, Danny C.; DeBoer, David; Lacki, Brian C.; Czech, Daniel J.; Croft, Steve; Gajjar, Vishal; Isaacson, Howard; Lebofsky, Matt; MacMahon, David H. E.; Ng, Cherry; Perez, Karen I.; Siemion, Andrew P. V.; Webb, Claire Isabel; Zic, Andrew; Drew, Jamie; Worden, S. Pete (November 2021). "Analysis of the Breakthrough Listen signal of interest blc1 with a technosignature verification framework". Nature Astronomy. 5 (11): 1153–1162. arXiv:2111.06350. Bibcode:2021NatAs...5.1153S. doi:10.1038/s41550-021-01508-8. ISSN 2397-3366. S2CID 239906760.</ref>

Capabilities for detecting technosignatures with recent, ongoing, and future missions and facilities. Cells colored green indicate that at least such a signature could be detectable for at least one stellar system and there being at least one peer-reviewed publication that has evaluated detectability of that signature.

It has been suggested that observatories on the Moon could be more successful.<ref>"Why Astronomers Want to Build a SETI Observatory on the Moon". Smithsonian Magazine. Retrieved 3 August 2022.</ref><ref>Williams, Matt. "The moon is the perfect spot for SETI". Universe Today. Retrieved 3 August 2022.</ref> In 2022, scientists provided an overview of the capabilities of ongoing, recent, past, planned and proposed missions and observatories for detecting various alien technosignatures.<ref>Axe, David (11 June 2022). "The Alien Hunter's Playbook Is Getting a Cutting-Edge Rewrite". The Daily Beast. Retrieved 19 July 2022.</ref><ref>Haqq-Misra, Jacob; Schwieterman, Edward W.; Socas-Navarro, Hector; Kopparapu, Ravi; Angerhausen, Daniel; Beatty, Thomas G.; Berdyugina, Svetlana; Felton, Ryan; Sharma, Siddhant; De la Torre, Gabriel G.; Apai, Dániel (1 September 2022). "Searching for technosignatures in exoplanetary systems with current and future missions". Acta Astronautica. 198: 194–207. arXiv:2206.00030. Bibcode:2022AcAau.198..194H. doi:10.1016/j.actaastro.2022.05.040. ISSN 0094-5765. S2CID 249240495.</ref>

Implications of detection

See also: Potential cultural impact of extraterrestrial contact

Steven J. Dick states that there generally are no principles for dealing with successful SETI detections. Detections of technosignatures may have ethical implications, such as conveying information related to astroethical<ref>Dick, Steven J. (August 8, 2018). "Astroethics and Cosmocentrism". Scientific American Blog Network. Retrieved 30 April 2021.</ref> and related machine ethics ones (e.g., related to machines' applied ethical values), or include information about alien societies or histories or fates, which may vary depending on the type, prevalence and form of the detected signature's technology. Moreover, various types of information about detected technosignatures and their distribution or dissemination may have varying implications that may also depend on time and context.

See also

• Laser SETI
• Quiet and loud aliens
• UFO Report (U.S. Intelligence)

Further reading

• Participants, NASA Technosignatures Workshop (28 January 2019). NASA and the Search for Technosignatures: A Report from the NASA Technosignatures Workshop. arXiv:1812.08681v2.