Difference between revisions 915792438 and 915987554 on enwiki

{{redirect|Goldilocks Zone|the more general principle|Goldilocks principle}}
{{redirect|Habitable zone|the galactic zone|Galactic habitable zone}}
{{short description|Zone around a star with strong possibilities for stable liquid water on a suitable planet}}
(contracted; show full)ot;Review 2009">{{cite journal |title=What makes a planet habitable? |journal=The Astronomy and Astrophysics Review |year=2009 |last=Lammer |first=H. |last2=Bredehöft |first2=J. H. |last3=Coustenis |first3=A. |last4=Khodachenko |first4=M. L. |volume=17 |issue=2 |pages=181–249 |doi=10.1007/s00159-009-0019-z |url=http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf |format=PDF |accessdate=2016-05-03 |bibcode=2009A&ARv..17..181L |display-authors=etal |
deadurl=yesurl-status=dead |archiveurl=https://web.archive.org/web/20160602235333/http://veilnebula.jorgejohnson.me/uploads/3/5/8/7/3587678/lammer_et_al_2009_astron_astro_rev-4.pdf |archivedate=2016-06-02 |df= }}</ref> as a second effect, induces the photodissociation of water vapor and the loss of hydrogen to space. The outer edge of the HZ is the distance from the star where adding more carbon dioxide to the atmosphere fails to keep the surface of the planet above the freezing point.<ref name="Review 2009"/>

===Solar System estimates===
Estimates for the habitable zone within the Solar System range from 0.38 to 10.0 [[astronomical units]],<ref name=zsom-2013 /><ref name= rayeric-2011 /><ref name= rk-2017 /><ref>{{cite web| url=http://depts.washington.edu/naivpl/sites/default/files/hz.shtml| title=Stellar habitable zone calculator| publisher=[[University of Washington]]| accessdate=17 December 2015}}</ref> though arriving at these estimates has been challenging for a variety of reasons. Numerous planetary mass objects orbit within, or close to, this range and as such receive sufficient sunlight to raise temperatures above the freezing point of water. However their atmospheric conditions vary substantially. The aphelion of Venus, for example, touches the inner edge of the zone and while atmospheric pressure at the surface is sufficient for liquid water, a strong greenhouse effect raises surface temperatures to {{convert|462|C|F}} at which water can only exist as vapour.<ref name=venus-2006>{{cite web|url=http://burro.cwru.edu/stu/advanced/venus.html |title=Venus |publisher=Case Western Reserve University |date=13 September 2006 |accessdate=2011-12-21 |deadurl=yesurl-status=dead |archiveurl=https://web.archive.org/web/20120426064658/http://burro.cwru.edu/stu/advanced/venus.html |archivedate=2012-04-26 |df= }}</ref> The entire orbits of the [[Moon]],<ref name=sharp>{{cite web |url=http://www.space.com/18067-moon-atmosphere.html |title=Atmosphere of the Moon |publisher=TechMediaNetwork |work=Space.com |accessdate=April 23, 2013 |author=Sharp, Tim}}</ref> [[Mars]],<ref name="bolonkin09">{{Cite book|first=Alexander A.|last=Bolonkin|date=2009|title=Artificial Environments on Mars|publisher=Springer |place=Berlin Heidelberg|pages=599–625|isbn=978-3-642-03629-3}}</ref> and nu(contracted; show full)uary 18, 2014 }}</ref><ref name=voanews>{{cite web|url=http://www.voanews.com/english/news/science-technology/NASA-Finds-Possible-Signs-of-Flowing-Water-on-Mars-126807133.html|title=NASA Finds Possible Signs of Flowing Water on Mars|publisher=voanews.com|accessdate=August 5, 2011}}</ref><ref name=mag>{{cite web|url=http://news.sciencemag.org/sciencenow/2011/08/is-mars-weeping-salty-tears.html|title=Is Mars Weeping Salty Tears?|publisher=news.sciencemag.org|accessdate=August 5, 2011|
deadurl=yesurl-status=dead|archiveurl=https://web.archive.org/web/20110814065220/http://news.sciencemag.org/sciencenow/2011/08/is-mars-weeping-salty-tears.html|archivedate=August 14, 2011|df=}}</ref><ref name="NASA-20131210">{{cite web |last1=Webster |first1=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Spacecraft Reveals a More Dynamic Red Planet |url=http://www.jpl.nasa.gov/news/news.php?release=2013-361&1#1 |date=December 10, 2013 |work=[[NASA]] |accessdate=December 10, 2013 }}</ref> no confirmation has been made of the presence of liquid water there. While other objects orbit partly within this zone, including comets, [[Ceres (dwarf planet)|Ceres]]<ref (contracted; show full)publisher=SPACE.com| date=June 22, 2000| accessdate=December 19, 2010}}</ref><ref name='Willson 2018'>{{cite web|url=https://www.space.com/8642-flashback-water-mars-announced-10-years.html |title=Flashback: Water on Mars Announced 10 Years Ago| publisher=SPACE.com| date=June 22, 2010| accessdate=May 13, 2018}}</ref><ref>{{cite web| url=https://science.nasa.gov/headlines/y2001/ast05jan_1.htm| title=Science@NASA, The Case of the Missing Mars Water| accessdate=March 7, 2009| 
deadurl=yesurl-status=dead| archiveurl=https://web.archive.org/web/20090327234049/https://science.nasa.gov/headlines/y2001/ast05jan_1.htm| archivedate=March 27, 2009| df=}}</ref> [[4 Vesta|Vesta]]<ref name="ScullyRussell2015">{{cite journal|last1=Scully|first1=Jennifer E.C.|last2=Russell|first2=Christopher T.|last3=Yin|first3=An|last4=Jaumann|first4=Ralf|last5=Carey|first5=Elizabeth|last6=Castillo-Rogez|first6=Julie|last7=McSween|first7=Harry Y.|last8=Raymond|first8=Carol A.|last9=Reddy|first9=Vishnu|last10=Le Corre|first10=Lucille|title=Geomorphological evidence for transient water flow on Vesta|journal=Earth and Planetary Science Letters|volume=411|y(contracted; show full)><ref>{{cite web |title=AstronomyCast episode 40: American Astronomical Society Meeting, May 2007 |work=Universe Today |last1=Cain |first1=Fraser |last2=Gay |first2=Pamela |authorlink2=Pamela L. Gay |url=http://media-c02m01.libsyn.com/podcasts/c50d001e8872db18d96cd44a73adccdc/46762eec/astronomycast/AstroCast-070611.mp3 |archive-url=https://wayback.archive-it.org/all/20070926102556/http://media-c02m01.libsyn.com/podcasts/c50d001e8872db18d96cd44a73adccdc/46762eec/astronomycast/AstroCast-070611.mp3 |
dead-url=yesurl-status=dead |archive-date=2007-09-26 |date=2007 |accessdate=2007-06-17 |df= }}</ref>

Once a star has evolved sufficiently to become a red giant, its circumstellar habitable zone will change dramatically from its main-sequence size.<ref>{{cite web| url=http://www.astrobio.net/topic/solar-system/sun/living-in-a-dying-solar-system-part-1/ |title=Living in a Dying Solar System, Part 1| publisher=Astrobiology| language=English|author=Ray Villard|date=27 July 2009|accessdate=8 April 2016}}</ref> For example, the Sun is expected to engulf the previously-habitable Earth(contracted; show full)enstein concluded that there are roughly 500 million habitable planets in the Milky Way.<ref name="BorensteinS">{{cite news |last1=Borenstein |first1=Seth |title=Cosmic census finds crowd of planets in our galaxy |agency=Associated Press |date=19 February 2011 |url=http://apnews.excite.com/article/20110219/D9LG45NO0.html |accessdate=24 April 2011 |archive-url=https://web.archive.org/web/20110927053134/http://apnews.excite.com/article/20110219/D9LG45NO0.html |archive-date=27 September 2011 |
dead-url=yesurl-status=dead }}</ref> NASA's [[Jet Propulsion Laboratory]] 2011 study, based on observations from the ''[[Kepler (spacecraft)|Kepler]]'' mission, raised the number somewhat, estimating that about "1.4 to 2.7 percent" of all stars of spectral class [[F-type main-sequence star|F]], [[G-type main-sequence star|G]], and [[orange dwarf|K]] are expected to have planets in their CHZs.<ref name="ChoiCQ">{{cite web |last1=Choi |first1=Charles Q.|url=http://www.space.com/1(contracted; show full)f]] was discovered within the CHZ of its host star [[55 Cancri|55 Cancri A]].<ref name="ScienceDaily">{{cite web |url = https://www.sciencedaily.com/releases/2007/11/071106133058.htm |title = Astronomers Discover Record Fifth Planet Around Nearby Star 55 Cancri |publisher = Sciencedaily.com |date = November 6, 2007 |accessdate = 2008-09-14| archiveurl = https://web.archive.org/web/20080926142319/https://www.sciencedaily.com/releases/2007/11/071106133058.htm| archivedate = 26 September 2008 
<!--DASHBot-->| deadurl = no| url-status = live}}</ref><ref name="Fischer2008">{{Cite journal |title=Five Planets Orbiting 55 Cancri |url=http://iopscience.iop.org/0004-637X/675/1/790/fulltext/ |last1=Fischer |first1=Debra A. |last2=Marcy |first2=Geoffrey W. |last3=Butler |first3=R. Paul |last4=Vogt |first4=Steven S. |last5=Laughlin |first5=Greg |last6=Henry |first6=Gregory W. |last7=Abouav |first7=David |last8=Peek |first8=Kathryn M. G. |last9=Wright |first9=Jason T. |display-authors=1 |journal=The Astrophysical Journal |date=2008 |volume=675 |issue=1 |pages=790–801 |arxiv=0712.3917 |bibcode=2008ApJ...675..790F |doi=10.1086/525512 }}</ref> Hypothetical satellites with sufficient mass and composition are thought to be able to support liquid water at their surfaces.<ref name="guardian">{{cite news| url=https://www.theguardian.com/science/2007/nov/07/spaceexploration |title=Could this be Earth's near twin? Introducing planet 55 Cancri f |newspaper=[[The Guardian]] |author=Ian Sample, science correspondent |date= 7 November 2007|accessdate=17 October 2008 |location=London| archiveurl= https://web.archive.org/web/20081002080911/http://www.guardian.co.uk/science/2007/nov/07/spaceexploration| archivedate= 2 October 2008 <!--DASHBot-->| deadurl= no| url-status= live}}</ref>

Though in theory such giant planets could possess moons, the technology did not exist to detect moons around them, and no extrasolar moons had been detected. Planets within the zone with the potential for solid surfaces were therefore of much greater interest.

===Habitable super-Earths===
{{Category see also|Super-Earths in the habitable zone}}
[[File:Gliese 581 - 2010.jpg|thumb|The [[habitable zone]] of Gliese 581 compared with our Solar System's habitable zone.]]
(contracted; show full)-setting.html |date=26 April 2012 |publisher=Skymania News |accessdate=27 April 2012 }}</ref><ref name="EGU-20120426">{{cite web |last1=de Vera |first1=J.-P. |last2=Kohler |first2=Ulrich |title=The adaptation potential of extremophiles to Martian surface conditions and its implication for the habitability of Mars |url=http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |date=26 April 2012 |publisher=[[European Geosciences Union]] |accessdate=27 April 2012 |
deadurl=yesurl-status=dead |archiveurl=https://web.archive.org/web/20120504224706/http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |archivedate=4 May 2012 |df= }}</ref><ref name="Onofride Vera2015">{{cite journal|last1=Onofri|first1=Silvano|last2=de Vera|first2=Jean-Pierre|last3=Zucconi|first3=Laura|last4=Selbmann|first4=Laura|last5=Scalzi|first5=Giuliano|last6=Venkateswaran|first6=Kasthuri J.|last7=Rabbow|first7=Elke|last8=de la Torre|first8=Rosa|last9=Horneck|first9=Gerda|title=Survival of Antarctic Cryptoendolithic Fungi in Simulated Martian Conditions On Board the International Space Station|journal=Astrobiology|volume=15|issue=12|year=2(contracted; show full){cite news|url = https://www.telegraph.co.uk/news/newstopics/howaboutthat/3166709/Messages-from-Earth-sent-to-distant-planet-by-Bebo.html|title = Messages from Earth sent to distant planet by Bebo |last = Moore |first = Matthew|date = October 9, 2008|publisher = .telegraph.co.uk|accessdate = 2008-10-09| archiveurl = https://web.archive.org/web/20081011142445/http://www.telegraph.co.uk/news/newstopics/howaboutthat/3166709/Messages-from-Earth-sent-to-distant-planet-by-Bebo.html|archivedate = 11 October 2008 
<!--DASHBot-->| deadurl = no| url-status = live |location=London}}</ref> and [[Hello From Earth]] in 2009, were directed to the Gliese 581 system, containing three planets in the CHZ—Gliese 581 c, d, and the unconfirmed g.
{{Clear}}

==See also==
{{Portal|Astronomy|Space}}
{{div col}}
*{{annotated link|Hypothetical types of biochemistry}}
*{{annotated link|Earth analog}}
(contracted; show full)
*{{cite web |url=http://phl.upr.edu/projects/habitable-exoplanets-catalog |title=The Habitable Exoplanets Catalog |publisher=PHL/University of Puerto Rico at Arecibo}}
*{{cite web |url=http://www.hzgallery.org/ |title=The Habitable Zone Gallery}}
*{{cite web |url=http://www.solstation.com/habitable.htm |title=Stars and Habitable Planets |publisher=SolStation |
deadurl=yesurl-status=dead |archiveurl=https://web.archive.org/web/20110628175616/http://www.solstation.com/habitable.htm |archivedate=2011-06-28 |df= }}
*{{cite journal |title=On the Galactic Habitable Zone|author1=Nikos Prantzos|doi=10.1007/s11214-007-9236-9|date=2006 |journal=Space Science Reviews |volume=135 |issue=1–4|pages=313–322|arxiv=astro-ph/0612316|bibcode = 2008SSRv..135..313P }}
*[http://btc.montana.edu/ceres/astrobiology/files/HabitableZone.htm Interstellar Real Estate: Location, Location, Location – Defining the Habitable Zone]
(contracted; show full){{authority control}}

[[Category:Search for extraterrestrial intelligence]]
[[Category:Planetary habitability]]
[[Category:Astronomical hypotheses]]
[[Category:Extraterrestrial life]]
[[Category:Articles containing video clips]]
[[Category:Extraterrestrial water]]