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There are several methods currently used by astronomers to detect distant [[exoplanet]]s from [[Earth]].<ref name="NASA-2020">{{cite web |author=Staff |title=5 Ways to Find a Planet |url=https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet/ |date=2020 |work=[[NASA]] |accessdate=24 October 2020 }}</ref> As well, some of these same methods, theoretically at least, may be used to detect the Earth as an exoplanet from distant star systems.
In June 2021, astronomers identified 1,715 stars (with likely related [[Planetary system|exoplanetary systems]]) within 326 [[light-year]]s (100 [[parsec]]s) that have a favorable positional vantage point—in relation to the Earth Transit Zone (ETZ)—of detecting [[Earth]] as an [[exoplanet]] [[Transit (astronomy)|transiting]] the [[Sun]] since the beginnings of human civilization (about 5,000 years ago); an additional 319 stars are expected to arrive at this special vantage point in the next 5,000 years.<ref name="NAT-20210623">{{cite journal |last1=Kaltenegger |first1=L. | author-link = Lisa Kaltenegger | last2=Faherty |first2=J.K.|title=Past, present and future stars that can see Earth as a transiting exoplanet |url=https://www.nature.com/articles/s41586-021-03596-y |date=23 June 2021 |journal=[[Nature (journal)|Nature]] |volume=594 |issue=7864 |pages=505–507 |doi=10.1038/s41586-021-03596-y |pmid=34163055 |bibcode=2021Natur.594..505K |accessdate=23 June 2021 |arxiv=2107.07936 }}</ref> Seven known [[exoplanet]] hosts, including [[Ross 128]], may be among these stars. [[Teegarden's Star]] and [[Trappist-1]] may be expected to see the Earth in 29 and 1,642 years, respectively, according to the astronomers. Radio waves, from humans, have reached over 75 of the closest stars that were studied.<ref name="NAT-20210623" /> Also in June 2021, other astronomers reported identifying 29 planets in [[habitable zone]]s that may be capable of observing the Earth.<ref name="TG20210623">{{cite news |last=Sample |first=Ian |title=Scientists identify 29 planets where aliens could observe Earth - Astronomers estimate 29 habitable planets are positioned to see Earth transit and intercept human broadcasts |url=https://www.theguardian.com/science/2021/jun/23/scientists-identify-29-planets-where-aliens-could-observe-earth |date=23 June 2021 |work=[[The Guardian]] |accessdate=23 June 2021 }}</ref> Earlier, in October 2020, astronomers had initially identified 508 such stars within 326 [[light-year]]s (100 [[parsec]]s) that would have a favorable positional vantage point—in relation to the Earth Transit Zone (ETZ)—of detecting [[Earth]] as an [[exoplanet]] [[Transit (astronomy)|transiting]] the [[Sun]].<ref name="RAS-20201020">{{cite journal |last1=Kaltenegger |first1=L. |last2=Pepper |first2=J. |title=Which stars can see Earth as a transiting exoplanet? |url=https://academic.oup.com/mnrasl/article/499/1/L111/5931805 |date=20 October 2020 |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=499 |issue=1 |pages=L111–L115 |doi=10.1093/mnrasl/slaa161 |arxiv=2010.09766 |accessdate=24 October 2020 |doi-access=free }}</ref><ref name="LS-20201022">{{cite news |last=Letzer |first=Rafi |title=Aliens on 1,000 nearby stars could see us, new study suggests |url=https://www.livescience.com/aliens-spot-earth-exoplanets.html |date=22 October 2020 |work=[[Live Science]] |accessdate=24 October 2020 }}</ref><ref name="COR-20201021">{{cite news |last=Friedlander |first=Blaine |title=Smile, wave: Some exoplanets may be able to see us, too |url=https://news.cornell.edu/stories/2020/10/smile-wave-some-exoplanets-may-be-able-see-us-too |date=21 October 2020 |work=[[Cornell University]] |accessdate=24 October 2020 }}</ref><ref name="FRBS-20201022">{{cite news |last=Carter |first=Jamie |title=Are We Being Watched? There Are 509 Star Systems With A Great View Of Life On Earth, Say Scientists |url=https://www.forbes.com/sites/jamiecartereurope/2020/10/22/are-we-being-watched-there-are-509-star-systems-with-a-great-view-of-life-on-earth-say-scientists/amp/ |date=22 October 2020 |work=[[Forbes]] |accessdate=24 October 2020 }}</ref>
According to researchers, the transit method is the most popular tool used to detect exoplanets and the most common tool to [[Astronomical spectroscopy|spectroscopically]] analyze [[Extraterrestrial_atmosphere#Exoplanets|exoplanetary atmospheres]].<ref name="RAS-20201020" /> As a result, such studies, based on the transit method, will be useful in the [[Extraterrestrial life|search for life on exoplanets]] beyond our [[Solar System]] by the [[Search for extraterrestrial intelligence|SETI program]], [[Breakthrough Listen|Breakthrough Listen Initiative]], as well as, upcoming exoplanetary [[Transiting Exoplanet Survey Satellite|TESS mission]] searches.<ref name="RAS-20201020" />
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