Detecting Earth from distant star-based systems: Difference between revisions

Revision as of 13:42, 21 October 2023

Revision as of 13:46, 21 October 2023

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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> Theoretically, some of these same methods may be used to detect the Earth as an exoplanet from distant star systems.

==History==

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.|author2-link=Jackie Faherty|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 |s2cid=235626242 }}</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. Radio waves, emitted by humans, have reached over 75 of the closest stars that were studied.<ref name="NAT-20210623" /> In June 2021, 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>

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Studies have suggested that radio broadcast leakage – with the program material likely not being detectable – may be a technosignature detectable at distances of up to a hundred light years with technology equivalent to the [[Square Kilometer Array]]<ref>{{cite web |title=How Far Into Space Can Radio Telescopes Hear? |url=https://www.forbes.com/sites/quora/2017/01/27/how-far-into-space-can-radio-telescopes-hear/ |website=Forbes |access-date=9 April 2021 |language=en}}</ref> if the ___location of Earth is known.<ref>{{cite journal |title=A direct communication proposal to test the Zoo Hypothesis |journal=Space Policy |date=1 November 2016 |volume=38 |pages=22–26 |doi=10.1016/j.spacepol.2016.06.001 |language=en |issn=0265-9646 |quote="While the limits of detection of Earth's radio transmissions are a subject of debate (Sullivan argues ~25 light-years, Atri et al. (2011) and Baum et al. (2011) up to 100 light years), as they largely depend on the size of the receiving antenna"|doi-access=free |last1=De Magalhães |first1=João Pedro |arxiv=1509.03652 |bibcode=2016SpPol..38...22D }}</ref><ref name="JCAP-2007">{{cite journal |last1=Loeb |first1=Avi |last2=Zaldarriaga|first2=Matias |title=Eavesdropping on radio broadcasts from galactic civilizations with upcoming observatories for redshifted 21 cm radiation |url=https://iopscience.iop.org/article/10.1088/1475-7516/2007/01/020/fulltext/ |journal=[[Journal of Cosmology and Astroparticle Physics]] |date=22 January 2007 |volume=2007 |page=020 |doi=10.1088/1475-7516/2007/01/020 |access-date=9 April 2021|arxiv=astro-ph/0610377 }}</ref><ref name="10.1007/978-94-009-9115-6_20"/> Likewise, if Earth's ___location can be and is known, it may be possible to use atmospheric analysis to detect life or favorable conditions for it on Earth via [[biosignature]]s, including [[MERMOZ|MERMOZ instruments]] that may be capable of remotely detecting living matter on Earth.<ref name="AA-2021">{{cite journal |author=Patty, C.H.L. |display-authors=et al. |title=Biosignatures of the Earth I. Airborne spectropolarimetric detection of photosynthetic life |url=https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/202140845 |date=2021 |journal=[[Astronomy & Astrophysics]] |volume=A68 |page=651 |doi=10.1051/0004-6361/202140845 |accessdate=21 June 2021 |arxiv=2106.00493 |bibcode=2021A&A...651A..68P |s2cid=235265876 }}</ref><ref name="ARX-20210601">{{cite journal|author=Patty, C.H. Luca |display-authors=et al. |title=Biosignatures of the Earth |journal=Astronomy & Astrophysics |date=1 June 2021 |volume=651 |pages=A68 |doi=10.1051/0004-6361/202140845 |arxiv=2106.00493v1 |s2cid=235265876 }}</ref><ref name="STD-20210620">{{cite news |author=[[University of Bern]] |title=Scientists Use New Technology to Detect Signatures of Life Remotely |url=https://scitechdaily.com/scientists-use-new-technology-to-detect-signatures-of-life-remotely/amp/ |date=20 June 2021 |work=SciTechDaily.com |accessdate=21 June 2021 }}</ref>

==Detecting life on Earth from afar==

In October 2023, an overview of detecting life on the planet Earth from afar was reported.<ref name="NAT-20231016">{{cite journal |last=Witze |first=Alexandria |title=How would we know whether there is life on Earth? This bold experiment found out - Thirty years ago, astronomer Carl Sagan convinced NASA to turn a passing space probe’s instruments on Earth to look for life — with results that still reverberate today. |url=https://www.nature.com/articles/d41586-023-03230-z |date=16 October 2023 |journal=[[Nature (journal)|Nature]] |volume=622 |pages=451-452 |doi=10.1038/d41586-023-03230-z |url-status=live |archiveurl=https://archive.ph/nVVIZ |archivedate=19 October 2023 |accessdate=21 October 2023 }}</ref>