Gliese 581e

{{Short description|Terrestrial planet orbiting Gliese 581}} {{Infobox planet | name = Gliese 581e | image = Exoplanet Comparison Gliese 581 e.png | caption = Size comparison of Gliese 581e with Earth<br/>(Based on selected hypothetical [[:File:Exoplanet Comparison Gliese 581 e.png#Summary|modeled compositions]]){{efn|The estimated range of sizes in this image from 2009 is based on the planet's [[minimum mass]]. Since the true mass is now known to be somewhat greater, the sizes may be underestimated.}}  | discovery_ref = <ref name="mayor"/> | discoverer = [[Michel Mayor|Mayor]] et al. | discovery_site = [[La Silla Observatory]], [[Chile]] | discovered = 21 April 2009 | discovery_method = [[Radial velocity]]   | orbit_ref = <ref name="vonStauffenberg2024"/> | apsis = astron | semimajor = {{val|0.02799|0.0003|ul=AU}} | eccentricity = {{val|0.012|0.015|0.008}} | period = {{val|3.1481|0.0004|ul=d}} | inclination = {{val|47|15|13|u=deg}} | time_periastron = 2454752.33 ± 0.05<ref name="robertson2014"/> | arg_peri = {{val|226|91|55|u=deg}} | semi-amplitude = {{val|1.8|0.1|ul=m/s}} | star = [[Gliese 581]]  | physical_ref = <ref name="vonStauffenberg2024"/> | mass = {{val|2.48|0.70|0.42|ul=Earth mass}}   }} '''Gliese 581e''' {{IPAc-en|ˈ|ɡ|l|iː|z|ə}} or '''Gl 581e''' is an [[exoplanet]] orbiting within the [[Gliese 581]] system, located {{convert|20.5|ly|pc|lk=on|abbr=off}} away from [[Earth]] in the [[Libra constellation]]. It is the third planet discovered in the system (fourth if the disputed planet candidate [[Gliese 581d]] is included) and the first in order from the star.

== Discovery == The planet was [[Discovery (observation)|discovered]] by an [[Observatory of Geneva]] team led by [[Michel Mayor]], using the [[High Accuracy Radial Velocity Planet Searcher|HARPS]] instrument on the [[European Southern Observatory]] {{convert|3.6|m|in|abbr=on}} [[telescope]] in [[La Silla Observatory|La Silla]], [[Chile]]. The discovery was announced on 21 April 2009. Mayor's team employed the [[radial velocity]] technique, in which the orbit size and [[mass]] of a [[planet]] are determined based on the small perturbations it induces in its parent star's [[orbit]] via [[Gravitation|gravity]].<ref name="mayor"/>

== Characteristics == With a [[minimum mass]] of about 1.9 [[Earth mass]]es, Gliese 581e was the least massive exoplanet known around a normal star at the time of discovery in 2009, with only [[PSR B1257+12 A]] being less massive.<ref>{{cite web|last=Rincon|first=Paul|author2=Amos, Jonathan|url=http://news.bbc.co.uk/1/hi/sci/tech/8008683.stm|title=Lightest exoplanet is discovered|publisher=[[BBC]]|date=2009-04-21|access-date=2009-04-21|archive-date=2009-04-24|archive-url=https://web.archive.org/web/20090424061149/http://news.bbc.co.uk/1/hi/sci/tech/8008683.stm|url-status=live}}</ref><ref>{{cite news |first=Dennis |last=Overbye |title=Astronomers Find Planet Closer to Size of Earth |url=https://www.nytimes.com/2009/04/22/science/22planet.html |work=[[New York Times]] |date=April 21, 2009 |access-date=February 24, 2017 |archive-date=March 12, 2017 |archive-url=https://web.archive.org/web/20170312213033/http://www.nytimes.com/2009/04/22/science/22planet.html |url-status=live }}</ref> A 2024 study determined the [[orbital inclination]] of the planet, allowing its true mass to be determined, which is about 30% greater than the minimum mass at about 2.5 Earth masses.<ref name="vonStauffenberg2024"/>

Gliese 581e completes an orbit around its parent star in 3.15 days. At an orbital distance of just {{convert|0.028|AU|km|abbr=on|lk=in}} from its parent star, it orbits further in than the [[habitable zone]].<ref name="robertson2014"/> Although scientists think it probably has a rocky surface similar to Earth, it is also likely to experience intense tidal heating similar to (and likely more intense than) that affecting Jupiter's moon [[Io (moon)|Io]].<ref>{{cite journal| last1 = Barnes | first1 = Rory| last2 = Jackson | first2 = Brian| last3 = Greenberg | first3 = Richard| last4 = Raymond | first4 = Sean N. |title=Tidal Limits to Planetary Habitability|date=2009-06-09| doi = 10.1088/0004-637X/700/1/L30| journal = The Astrophysical Journal| volume = 700| issue = 1| pages = L30–L33|arxiv=0906.1785|bibcode = 2009ApJ...700L..30B | s2cid = 16695095}}</ref>

== See also == *[[Habitability of red dwarf systems]]

== Notes == {{notelist}}

== References == {{reflist|2|refs=

<ref name="mayor">{{cite journal |doi=10.1051/0004-6361/200912172 |bibcode=2009A&A...507..487M |journal=[[Astronomy and Astrophysics]] |volume=507 |issue=1 |year=2009 |pages=487–494 |last1=Mayor |first1=Michel |last2=Bonfils |first2=Xavier |last3=Forveille |first3=Thierry |last4=Delfosse |first4=Xavier |last5=Udry |first5=Stéphane |last6=Bertaux |first6=Jean-Loup |last7=Beust |first7=Hervé |last8=Bouchy |first8=François |last9=Lovis |first9=Christophe |last10=Pepe |first10=Francesco |last11=Perrier |first11=Christian |last12=Queloz |first12=Didier |last13=Santos |first13=Nuno C. |title=The HARPS search for southern extra-solar planets, XVIII. An Earth-mass planet in the GJ 581 planetary system |arxiv=0906.2780 |display-authors=3 |url=http://obswww.unige.ch/~udry/Gl581_preprint.pdf |s2cid=2983930 |url-status=dead |archive-url=https://web.archive.org/web/20090521052641/http://obswww.unige.ch/~udry/Gl581_preprint.pdf |archive-date=21 May 2009 }}</ref>

<ref name="robertson2014">{{cite journal|last1=Robertson |first1=Paul |author2-link=Suvrath Mahadevan |last2=Mahadevan |first2=Suvrath |last3=Endl |first3=Michael |last4=Roy |first4=Arpita |title=Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581 |journal=[[Science (journal)|Science]] |date=3 July 2014 |doi=10.1126/science.1253253 |arxiv=1407.1049 |bibcode=2014Sci...345..440R |volume=345 |issue=6195 |pages=440–444 |pmid=24993348|s2cid=206556796 }}</ref>

<ref name="vonStauffenberg2024">{{cite journal|last1=von Stauffenberg|first1=A.|last2=Trifonov|first2=T.|last3=Quirrenbach|first3=A.|last4=Reffert|first4=S.|last5=Kaminski|first5=A.|last6=Dreizler|first6=S.|last7=Ribas|first7=I.|last8=Reiners|first8=A.|last9=Kürster|first9=M.|last10=Twicken|first10=J. D.|last11=Rapetti|first11=D.|last12=Caballero|first12=J. A.|last13=Amado|first13=P. J.|last14=Béjar|first14=S. V. J.|last15=Cifuentes|first15=C.|last16=Góngora|first16=S.|last17=Hatzes|first17=A. P.|last18=Henning|first18=Th.|last19=Montes|first19=D.|last20=Morales|first20=J. C.|last21=Schweitzer|first21=A.|display-authors=3|title=The CARMENES search for exoplanets around M dwarfs. Revisiting the GJ 581 multi-planetary system with new Doppler measurements from CARMENES, HARPS, and HIRES|journal=Astronomy & Astrophysics|date=2024-06-05|issn=0004-6361|arxiv=2407.11520|doi=10.1051/0004-6361/202449375|page=|bibcode=2024A&A...688A.112V }}</ref>

}}

== External links == {{commonscat-inline|Gliese 581 e}} {{wikinews-inline|Discovery of smallest exoplanet yields 'extraordinary' find}} *[https://web.archive.org/web/20090705084859/http://www.eso.org/public/outreach/press-rel/pr-2009/pr-15-09.html Lightest exoplanet yet discovered] [[European Southern Observatory]] press release *[https://news.yahoo.com/s/ap/20090421/ap_on_sc/eu_britain_new_planet Scientists discover a nearly Earth-sized planet] {{Webarchive|url=https://web.archive.org/web/20090429221450/http://news.yahoo.com/s/ap/20090421/ap_on_sc/eu_britain_new_planet |date=2009-04-29 }} *[http://exoplanet.eu/planet.php?p1=Gl+581&p2=e&showPubli=yes&sortByDate#a_publi Publications at Exoplanet.eu] {{Webarchive|url=https://web.archive.org/web/20110602113129/http://exoplanet.eu/planet.php?p1=Gl+581&p2=e&showPubli=yes&sortByDate#a_publi |date=2011-06-02 }}

{{DEFAULTSORT:Gliese 581E}} [[Category:Exoplanets discovered in 2009]] [[Category:Exoplanets in the Gliese Catalog]] [[Category:Exoplanets detected by radial velocity]] [[Category:Gliese 581]] [[Category:Near-Earth-sized exoplanets]] [[Category:Terrestrial planets]] [[Category:Libra (constellation)]]