MSGID: 1:317/3 6493ce66   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Exoplanet may reveal secrets about the edge of habitability    
      
     Date:   
         June 21, 2023   
     Source:   
         Cornell University   
     Summary:   
         How close can a rocky planet be to a star, and still sustain water   
         and life? A recently discovered exoplanet may be key to solving   
         that mystery.   
      
      
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   FULL STORY   
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   How close can a rocky planet be to a star, and still sustain water and   
   life? A recently discovered exoplanet may be key to solving that mystery.   
      
   "Super-Earth" LP 890-9c (also named SPECULOOS-2c) is providing important   
   insights about conditions at the inner edge of a star's habitable zone   
   and why Earth and Venus developed so differently, according to new   
   research led by Lisa Kaltenegger, associate professor of astronomy at   
   Cornell University.   
      
   Her team found LP 890-9c, which orbits close to the inner edge of its   
   solar system's habitable zone, would look vastly different depending on   
   whether it still had warm oceans, a steam atmosphere, or if it had lost   
   its water - - assuming it once had oceans like Earth's.   
      
   "Looking at this planet will tell us what's happening on this inner edge   
   of the habitable zone -- how long a rocky planet can maintain habitability   
   when it starts to get hot," Kaltenegger said. "It will teach us something   
   fundamental about how rocky planets evolve with increasing starlight,   
   and about what will one day happen to us and Earth."  Kaltenegger is   
   the lead author of "Hot Earth or Young Venus? A Nearby Transiting Rocky   
   Planet Mystery," published in Monthly Notices of the Royal Astronomical   
   Society: Letters.   
      
   LP 890-9c is one of two super-Earths orbiting a red dwarf star located   
   100 light years from Earth, researchers announced last year. They said   
   liquid water or an atmosphere rich in water vapor was possible on LP   
   890-9c, which is about 40% larger than Earth and circles the small,   
   cool star in 8.5 days.   
      
   Those criteria suggested it to be one of the best targets for JWST to   
   study among the known, potentially habitable terrestrial planets, in   
   addition to the TRAPPIST-1 system.   
      
   The team's models are the first to detail differences in the chemical   
   signatures generated by rocky planets near the habitable zone's interior   
   boundary, based on variables including the planet's size, mass, chemical   
   makeup, surface temperature and pressure, atmospheric height and cloud   
   cover.   
      
   The calculations were key to estimating how much time JWST would need   
   to confirm the basic composition of an atmosphere -- if there is one.   
      
   The models span several scenarios thought to reflect stages of rocky   
   planets' evolution, ranging from a "hot Earth" where life might still be   
   possible, to a desolate Venus featuring a carbon dioxide atmosphere. In   
   between are phases Earth is expected to experience as the sun grows   
   brighter and hotter with age, causing the oceans to gradually evaporate   
   and fill the atmosphere with steam before boiling off entirely.   
      
   How long those processes might take is unknown, and the astronomers say   
   LP 890- 9c provides a rare opportunity to explore that evolution.   
      
   "This planet is the first target where we can test these different   
   scenarios," Kaltenegger said. "If it's still a hotter Earth -- hot,   
   but with liquid water and conditions for life -- then the timeline is   
   slower than we thought. If we see that it's already a full-blown Venus,   
   then the water gets lost fast."  It's possible that LP 890-9c has no   
   atmosphere and hosts no life, or that it resembles a Venus with thick   
   clouds that would block light from reflecting and thus yield little   
   information. Deeper investigation promises to provide valuable clues,   
   Kaltenegger said.   
      
   "We don't know what this planet on the edge of habitability could be like,   
   so we have to look," she said. "This is what real exploration is about."   
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Extrasolar_Planets # Venus # Kuiper_Belt #   
                   Astronomy # Pluto # Solar_System # Stars #   
                   Asteroids,_Comets_and_Meteors   
       * RELATED_TERMS   
             o Extrasolar_planet o Uranus o Extraterrestrial_life o   
             Venus o Saturn o Gas_giant o Planetary_habitability o   
             Eris_(dwarf_planet)   
      
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   Story Source: Materials provided by Cornell_University. Original written   
   by James Dean, courtesy of the Cornell Chronicle. Note: Content may be   
   edited for style and length.   
      
      
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230621105434.htm   
      
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