Hycean Worlds: Difference between revisions

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#redirect [[Hycean world]]
[[File:Ocean Planet (19937982002).png | thumb | a hycean world would be a water planet, covered by a thick Hydrogen atmosphere.]]
A '''Hycean world''' is a proposed type of habitable world, first described in September 2021, in a paper published in ''[[The Astrophysical Journal]]''.<ref name=spaceflightinsider2021-09-05/><ref name=theguardian2021-08-26/>
 
These worlds, if they exist, would be larger than [[planet Earth]], and smaller than [[planet Neptune]].<ref name=spaceflightinsider2021-09-05/> 
They would have a thick ocean, where life might be found, covered by a thich [[Hydrogen]] atmosphere.
 
The [[habitable zone]] for a hycean world would be broader than that for a terrestrial habitable planet.<ref name=spaceflightinsider2021-09-05/>
 
As astronomer have hunted for exoplanets that could harbour life, the suitability of earth-sized planets orbiting small [[red dwarf]] stars has stirred debate.  Red dwarfs stars, while generally dimmer than Earth's sun [[Sol]], are prone to occasional massive [[stellar flares]], flares so large they would strip earth-sized planets of their atmospheres.  This concern would not affect ocean life on a water world.<ref name=spaceflightinsider2021-09-05/>
 
In addition, due to the smaller mass of red dwarf stars, their planets are likely to be [[tidally locked]] to the star, because they would orbit much more closely.  A hycean world tidally locked to a red dwarf, that was too close to its star for life on its surface, could have a ring of ocean at a temperature that could sustain life on its night side.<ref name=spaceflightinsider2021-09-05/> 
 
The authors of the paper, [[Nikku Madhusudhan]], [[Anjali A. A. Piette]] and [[Savvas Constantinou]], all of the [[University of Cambridge]], prepared a list of candidates that might be candidates for life bearing hycean worlds.<ref name=spaceflightinsider2021-09-05/> <ref name=AstrophysicalJournal2021-08-26/> They stated that the [[James Webb Space Telescope]] was capable of measuring [[biosignature]]s that, if found on these worlds, would suggest they had oceans harbouring life.<ref name=AstrophysicalJournal2021-08-26/>
 
''[[Spaceflight Insider]]'' reported some scientists believe that the biosignatures indicative of life on these planets might be found ''"within the next two to three years"''.<ref name=spaceflightinsider2021-09-05/>  ''The Guardian'', however, quoted [[Beth Biller]], of the [[Max-Planck Institute for Astronomy]], who, while she welcomed using the James Webb telescope to study hycean world candidates, noted that, since we already know planet Earth harbours life, we have confidence of what gases found in an Earth-like exoplanet would indicate life, we can't have that kind of confidence of the significance of the gases detected in mini-Neptune planets.<ref name=theguardian2021-08-26/> 
 
''[[The Cambridge Independent]]'' reported Madhusudhan's team developed its model for hycean planets while studying the exoplanet [[K2-18b]].<ref name=cambridgeindependent2021-09-02/>
 
According to ''[[The Guardian]]'' biosignatures would be more easily detected in the atmospheres of mini-Neptune sized planets, compared with smaller terrestrial planets, like planet Earth, due to their thicker atmospheres.<ref name=theguardian2021-08-26/>
 
==References==
{{reflist|refs=
<ref name=cambridgeindependent2021-09-02>
{{cite news   
| url        = https://www.cambridgeindependent.co.uk/news/hycean-planets-cambridge-astronomers-say-our-best-hope-for-9213871/
| title      = Hycean planets: Cambridge astronomers say our best hope for finding extraterrestrial life may have been hiding in plain sight
| work        = [[The Cambridge Independent]]
| author      = Paul Brackley
| date        = 2021-09-02
| archiveurl  = https://web.archive.org/web/20211015032537/https://www.cambridgeindependent.co.uk/news/hycean-planets-cambridge-astronomers-say-our-best-hope-for-9213871/
| archivedate = 2021-10-15
| accessdate  = 2022-02-13
| url-status  = live
| quote      = Their discovery came when Dr Madhusudhan’s team at the Institute of Astronomy studied a mini-Neptune called K2-18b.
}}
</ref>
 
<ref name=theguardian2021-08-26>
{{cite news   
| url        = https://www.theguardian.com/science/2021/aug/26/mini-neptune-beyond-solar-system-may-soon-yield-sign-life-hycean-exoplanet-cambridge-astronomer
| title      = ‘Mini-Neptunes’ beyond solar system may soon yield signs of life
| work        = [[The Guardian]]
| author      = Nicola Davis
| date        = 2021-08-26
| archiveurl  = https://web.archive.org/web/20220129141116/https://www.theguardian.com/science/2021/aug/26/mini-neptune-beyond-solar-system-may-soon-yield-sign-life-hycean-exoplanet-cambridge-astronomer
| archivedate = 2022-01-29
| accessdate  = 2022-02-13
| url-status  = live
| quote      = <!-- Researchers have mostly looked for planets of a similar size, mass, temperature and atmospheric composition to Earth. --> But University of Cambridge astronomers believe there may be more promising possibilities after recent work suggested that a “mini-Neptune” more than twice the radius of Earth and more than eight times as massive may also be habitable.
}}
</ref>
 
<ref name=spaceflightinsider2021-09-05>
{{cite news   
| url        = https://www.spaceflightinsider.com/space-flight-news/new-class-of-exoplanets-identified-in-search-for-extraterrestrial-life/           
| title      = New class of exoplanets identified in search for extraterrestrial life
| work        = [[Spaceflight Insider]]
| author      = Laurel Kornfeld
| date        = 2021-09-05
| archiveurl  = https://web.archive.org/web/20210905105212/https://www.spaceflightinsider.com/space-flight-news/new-class-of-exoplanets-identified-in-search-for-extraterrestrial-life/
| archivedate = 2021-09-05
| accessdate  = 2022-02-13
| url-status  = live
| quote      = Not present in our own solar system, these worlds are known as Hycean planets. They are typically up to 2.5 times larger than Earth, covered mostly or completely by oceans of liquid water, and have hydrogen-rich atmospheres. 
}}
</ref>
 
<ref name=AstrophysicalJournal2021-08-26>
{{cite journal   
| url        = https://iopscience.iop.org/article/10.3847/1538-4357/abfd9c/pdf
| title      = Habitability and Biosignatures of Hycean Worlds
| work        = [[The Astrophysical Journal]]
| author1    = Nikku Madhusudhan
| author2    = Anjali A. A. Piette
| author3    = Savvas Constantinou
| date        = 2021-08-26
| doi        = https://doi.org/10.3847/1538-4357/abfd9c
| pages      =
| archiveurl  =
| archivedate =
| accessdate  = 2022-02-13
| url-status  = live     
| quote      =
}}
</ref>
}}

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