Free Astronomy Magazine July-August 2025 ARABIC VERSION

parttothecaseofK2-18b.Granted, but not granted, that this planet is ahycean,theonlypeculiarcharac- teristic that it would have in com- mon with Earth would be that of havingliquidwateronthesurface. Foreverythingelse,itismuchdiffer- ent:ithasamassbetween7and10 timesgreater,aradius2.6timesthat of Earth, and a density that is less than half that of our planet. Even thestarthathostsK2-18b(124light yearsawayfromus)isvery different fromtheSun;itis,infact,ared dwarf(M2.5V),aroundwhichthe planet revolves in just 33 days at an average distance of 23.8 million km, or14.8millionmiles.(Thereisalsoa second known planet in the system, K2-18 c, which is irrelevant here.) SincethestarK2-18hasapproxi- mately half the mass and radius of the Sun, the energy flux per unit of surface area that K2-18 b receives is slightly lower than what the EarthreceivesfromtheSun;itfollows that K2-18 b orbits within the K2-18 habitable zone. This peculiarity has promptedresearcherstostudyit sinceitsdiscoveryin2015,whenit wasthe18 th exoplanettobediscov- eredduringtheextendedmissionof NASA’sKeplerSpaceTelescope(K2). The2023observations Althoughthesensationalannounce- mentofthepossibleexistenceoflife on K2-18 b did not go around the world until last April, the presence of DMS in the atmosphere of that planet had already been proposed in 2023, also on that occasion by Madhusudhan’s team. It all started evenearlier,in2019,whentheHub- bleSpaceTelescopehadtakenspec- tra of K2-18 b, revealing a thick atmosphere rich in hydrogen (H 2 ), clouds,andalsothepossibledetec- tionofwatervapor(H 2 O).Therea- sonwhywatervaporwasindicated onlyasa“possibledetection”isthat Hubblecanonlyseeasmallpartof ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 7 إﻋﻼن ﻣﻬﻤـﺔ K2 ـﺎسﺿـﻮﺋﻲ دﻗ ﻘـﺔ ﺎﺳـﺘﺨﺪام ﺗﻠﺴـ ﻮب ﻛﻴ ﻠـﺮﻗـﺪﻣﺖ ﺑ ﺎﻧـﺎت ﻗ اﻟﺘﺎ ﻌـﺔ ﻟﻨﺎﺳـﺎ واﻟـ ـﺪ ﻣـﻦ اﻟــﺤﻘﻮل اﻟﻤﺴـﺘﻬﺪﻓﺔ ﻓـﻲ ﻣﺴـ اﻟﺸـﻤﺲواﻛﺘﺸـﻔﺖ أﻛـ ﻣـﻦ ﻟﻠﻌﺪ 300 ﻮﻛـﺐ ﻧ ﻤـﻲ وﻣﺌـﺎت اﻟ ﻮاﻛﺐ اﻟﻨ ﻤ ﺔ اﻟﻤﺮﺷﺤﺔ . ــﻢ ﺣ ـــﻢ اﻟ ﻮﻛـــﺐ اﻟﻜـــﺮة اﻷرﺿـــ ﺔ ﻣﻘﺎرـــﺔً ﺑﺤ اﻟﻨ ﻤــﻲ K2-18b وﺻـــﻮرة ﻫـــﺬا اﻟ ﻮﻛـــﺐ ﻫـــﻲ ـﺚ ﻻ ﻤﻜﻨﻨــﺎ ﻣﻌﺮﻓــﺔ ﺷــ ﻠﮫ ﻣـﻦ ﻧﺴــﺞ اﻟـــﺨ ﺎل ﺣ اﻟـﺤﻘ ﻘﻲوﻻ ﺗﻔﺎﺻ ﻠﮫ اﻟﺴﻄﺤ ﺔ اﻟﻔﻌﻠ ﺔ . اﻷرض ارﺻﺎد ﻋ ﺎم 2023 ﻋـﺎﻟﻢ ـﺎء اﻟﻔ ـــــــــــﻮ ــــــــــﺔ ﻧﻴ اﻟﻔﻠﻜ ﻣﺎدﻫﻮﺳــــــﻮدان ﻘــــــــﻒﻻﻟﺘﻘــــــــﺎط ﺻــــــــــــــــﻮرة ﻓـــــــــــــــــﻲ ﻣﻌﻬـــــــــــــﺪ ﻋﻠــــــــــــــﻢ اﻟﻔﻠــــــــــــــــﻚ ﻓــــــــــــــــﻲ ﺟﺎﻣﻌــــــــــــــــــــــــــــــــــــــــــــــــــــﺔ ــــــــــــــــــــــــــــــــــــــــــﺪج ﺎﻣ إﻧﺠﻠــــــــــــــ ا أﺑﺮ ــــــــــــــﻞ 2025 . [Atlantic Studios viaAP] إذا اﻓﱰﺿــﻨﺎ أن ﻫــﺬا اﻟﻜﻮﻛــﺐ ﻣﻐﻄــﻰ ﺑﺎ ﺤﻴﻄﺎت وﻏﻼف ﺟﻮي ﻏﻨﻲ ﺑﺎﻟﻬﻴـﺪروﺟ ﻓﺈن اﻟﺴﻤﺔ اﻟﺘﻲ ﻳﺸﱰك ﻓ ﻴﻬﺎ ﻣﻊ اﻷرض ﻫﻲ وﺟﻮد ﻣﻴﺎه ﺳﺎﺋﻠﺔ ﻋﲆ ﺳﻄﺤﻪ أﻣـﺎ ﺑﺎﻟﻨ ﺴـﺒﺔ ﻷي ﳾء آﺧﺮ، ﻓﻬﻮ ﻣﺨﺘﻠـﻒ ﺗﻤﺎﻣـ : ﺎً ﻛﺘﻠﺘـﻪ أﻛﱪ ﺑـ 7 إﱃ 10 أﺿﻌﺎف وﻧﺼﻒ ﻗﻄﺮه أﻛـﱪ ﺑـ 2.6 ﻣﺮة ﻣﻦ ﻧﺼﻒ ﻗﻄﺮ اﻷرض وﻛﺜﺎﻓ ﺘـﻪ أﻗﻞ ﻣﻦ ﻧﺼﻒ ﻛﺜﺎﻓﺔ أرﺑﻌﺔ ﻛﻮاﻛﺐ ﺣﺘﻰ و ﺑﻞ اﻟﻨﺠﻢ اﻟﺬي ﻳﺤﺘﻀﻦ K2-18b ) اﻟﺬي ﻳﺒﻌﺪ ﻋﻨﺎ 124 ﺨﺘﻠﻒ ﻳ( ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﻋﻦ اﻟﺸﻤﺲ ﻓﻬﻮ ﰲ اﻟﻮاﻗﻊ ﻗﺰم أﺣﻤﺮ ) M2.5V ( ﻳﺪور اﻟﻜﻮﻛﺐ ﺣﻮﻟﻪ ﰲ 33 ﻳﻮﻣًﺎ ﻓﻘﻂ ﻋﲆ ﻣﺴﺎﻓﺔ ﻣﺘﻮﺳﻄﺔ ﺗﺒﻠﻎ 23.8 ﻣﻠﻴﻮن ﻛﻴﻠـﻮﻣﱰ أو 14.8 ﻣﻠﻴـﻮن ﻣﻴﻞ ﻫﻨﺎك أﻳﻀًﺎ ﻛﻮﻛﺐ ﺛﺎنٍ ﻣﻌﺮوف ﰲ اﻟﻨﻈﺎم وﻫﻮ K2-18c وﻫـﻮ ) ﻛﻮﻛـﺐ ﻻ ﻋﻼﻗـﺔ ﻟـﻪ ﺑﺎ ﻮﺿﻮع ﻫﻨﺎ ( وﺑﻤﺎ أن اﻟﻨﺠﻢ K2-18 ﻟﺪﻳـﻪ ﺎً ﺗﻘﺮﻳﺒ ﻧﺼﻒ ﻛﺘﻠﺔ وﻧﺼﻒ ﻗﻄﺮ اﻟﺸﻤﺲ ﻓﺈن ﺗـﺪﻓﻖ اﻟﻄﺎﻗـﺔ ﻟﻜـﻞ وﺣـﺪة ﻣـﻦ ا ﺴـﺎﺣﺔ اﻟﺴﻄﺤﻴﺔ اﻟﺘﻲ ﻳﺘﻠﻘﺎﻫـﺎ اﻟﻜﻮﻛـﺐ K2-18 b أﻗﻞ ﺑﻘﻠﻴﻞ ﻣﻤﺎ ﺗﺘﻠﻘـﺎه اﻷرض ﻣـﻦ اﻟﺸـﻤﺲ وﻳﱰﺗﺐ ﻋﲆ ذﻟﻚ أن اﻟﻜﻮﻛﺐ K2-18 b ﻳـﺪور داﺧﻞ ا ﻨﻄﻘﺔ اﻟﺼﺎﻟﺤﺔ ﻟﻠﺤﻴﺎة ﻟﻠﻨﺠﻢ K2-18 وﻗﺪ دﻓﻌﺖ ﻫـﺬه اﻟﺨﺼﻮﺻـﻴﺔ اﻟﺒـﺎﺣﺜ إﱃ دراﺳﺘﻪ ﻣﻨﺬ اﻛﺘﺸﺎﻓﻪ ﰲ ﻋـﺎم 2015 ﻋﻨـﺪﻣﺎ ﻛﺎن اﻟﻜﻮﻛﺐ رﻗﻢ 18 اﻟﺬي ﺗﻢ اﻛﺘﺸﺎﻓﻪ ﺧﻼل اﻟﺒﻌﺜﺔ ا ﻤﺘـﺪة ﻟﺘﻠﺴـﻜﻮب ﻛﻴﺒﻠـﺮ اﻟﻔﻀـﺎﺋﻲ ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أن اﻹﻋﻼن ا ﺜ ﻋـﻦ اﺣﺘﻤـﺎل وﺟﻮد ﺣﻴﺎة ﻋﲆ ﻛﻮﻛﺐ K2-18 b ﻟﻢ ﻳُﻨـ ﴩ ـ ﺣﺘﻰ أﺑﺮﻳﻞ ا ﺎﴈ إﻻ أن وﺟﻮد ﺛﻨﺎﺋﻲ ﻣﻴﺜﻴـﻞ اﻟﻜﱪﻳﺘﻴﺪ ﰲ اﻟﻐﻼف اﻟﺠﻮي ﻟﺬﻟﻚ اﻟﻜﻮﻛﺐ ﻛﺎن ﻗﺪ اﻗﱰُح ﺑﺎﻟﻔﻌﻞ ﰲ ﻋﺎم 2023 وذﻟـﻚ ﰲ ﺗﻠـﻚ ا ﻨﺎﺳﺒﺔ أﻳﻀًﺎ ﻣﻦ ﻗِﺒﻞ ﻓﺮﻳﻖ ﻣﺎدوﺳﻮدان . ﺑﺪأ ﻛـﻞ ﳾء ﰲ وﻗـﺖ ﺳـﺎﺑﻖ ﰲ ﻋـﺎم 2019 ﻋﻨـﺪﻣﺎ اﻟـﺘﻘﻂ ﺗﻠﺴـﻜﻮب ﻫﺎﺑـﻞ اﻟﻔﻀـﺎﺋﻲ أﻃﻴﺎف اﻟﻜﻮﻛﺐ K2-18 b ﻛﺎﺷﻔًﺎ ﻋﻦ ﻏﻼف ﺟﻮي ﺳـﻤﻴﻚ ﻏﻨـﻲ ﺑﺎﻟﻬﻴـﺪروﺟ واﻟﻐﻴـﻮم ﺑﺎﻹﺿﺎﻓﺔ إﱃ إﻣﻜﺎﻧﻴﺔ رﺻﺪ ﺑﺨﺎر ا ﺎء واﻟﺴﺒﺐ ﰲ اﻹﺷﺎرة إﱃ ﺑﺨـﺎر ا ـﺎء ﻓﻘـﻂ ﻛــ رﺻـﺪ " " ﻣﺤﺘﻤﻞ ﻫﻮ أن ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﻻ ﻳﺴـﺘﻄﻴﻊ ر ؤﻳﺔ ﺳﻮى ﺟﺰء ﺻﻐ ﻣـﻦ ﻃﻴـﻒ اﻷﺷـﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ﰲ ﻧﻄﺎق 1.1-1.7 . ﻣﻴﻜﺮون اﻟﺒﻌﺜﺔ ا ﻤﺘـﺪة ﻟﺘﻠﺴـﻜﻮب ﻛﻴﺒﻠـﺮ اﻟﻔﻀـﺎﺋﻲ اﻟﺘﺎﺑﻊ ﻟﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ (K2) اﻟﺘﻲ ﻗﺪﻣﺖ ﺑﻴﺎﻧﺎت ﻗﻴﻤﺔ ﺣﻮل اﻟﻜﻮا ﻛﺐ اﻟﻨﺠﻤﻴﺔ . ﻳﻮﻟﻴﻮ - ﺃﻏﺴﻄﺲ 2 0 2 5