Free Astronomy Magazine July-August 2025 ARABIC VERSION

This scenario has convinced scien- tists to include DMS among the mostinterestingbiosignaturemole- cules (about twenty in total) that we can expect to recognize in the atmospheres of exoplanets that host life, making it an important molecule to look for during trans- mission spectroscopy experiments. This technique, applicable to most exoplanets with atmospheres that transit in front of their star along ourlineofsight,essentiallyconsists in subtracting the spectrum of the starwhentheexoplanetisnottran- siting from the one taken during a transit.Thedifferenceprovidesin- formation on the nature of the gases present in the exoatmos- phere.Inpractice,atinyfractionof thestarlightpassesthroughtheat- mosphere of the exoplanet during transits before reaching the Earth. This passage leaves faint traces in the stellar spectrum, which as- tronomerscanpiecetogethertode- terminethegasesthatmakeupthe exoplanet’s atmosphere. Whatexactly isK2-18 b? Exactly,nooneknows.Thevarious teamsofresearcherswhohavestud- ied the planet so far have come to conflicting conclusions. Depending onthecomparisonmodels,K2-18b has turned out to be a super-Earth rather than a mini-Neptune or sub- Neptune. There is currently a con- troversial tendency to classify it asa “hycean” planet. This term was coined about four years ago by the sameteamofresearchers,ledby Professor Nikku Madhusudhan, who announcedthediscoveryofDMS intheK2-18batmosphere.Hycean is a syncretism of hydrogen and ocean , and indicates a planet en- tirely and solely covered by a very deep ocean of water, overlaid by a thick atmosphere composed essen- tially of hydrogen. Astronomers don’t know for sure whether these worldsactuallyexist,butthemodels thatdescribethemfitatleastin ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 6 ﻟﻘﺪ أﻗﻨﻊ ﻫﺬا اﻟﺴﻴﻨﺎرﻳﻮ اﻟﻌﻠﻤﺎء ﺑﺈدراج ﺛﻨﺎﺋﻲ ﻣﻴﺜﻴﻞ اﻟﻜﱪﻳﺘﻴﺪ ﺿﻤﻦ أﻛﺜـﺮ اﻟﺠﺰﻳﺌـﺎت ذات اﻟﺴﻤﺎت اﻟﺤﻴﻮﻳـﺔ إ ﺛـﺎرة ﻟﻼﻫﺘﻤـﺎم ) ﺣـﻮاﱄ ﻋﴩﻳﻦ ﺟﺰيء ﰲ ا ﺠﻤﻮع ( اﻟﺘـﻲ ﻳﻤﻜـﻦ أن ﻧﺘﻮﻗـﻊ اﻟﺘﻌـﺮف ﻋﻠﻴﻬـﺎ ﰲ أﻏﻠﻔــﺔ اﻟﻜﻮاﻛـﺐ اﻟﻨﺠﻤﻴﺔ اﻟﺘﻲ ﺗﺴﺘﻀﻴﻒ اﻟﺤﻴـﺎة ﺧﺎﺻـﺔ وأن اﻟﻜﺸﻒ ﻋﻨﻪ ﻳﺸ ﺑﻘﻮة إﱃ وﺟﻮد ﻣﺤﻴﻄـﺎت ﺳﺎﺋﻠﺔ ﻣﻤﺎ ﻳﺠﻌﻠﻪ ﺟﺰﻳﺌﺎً ﻣﻬﻤﺎ ﻟﻠﺒﺤـﺚ ﻋﻨـﻪ أﺛﻨﺎء ﺗﺠﺎرب اﻟﺘﺤﻠﻴﻞ اﻟﻄﻴﻔﻲ اﻟﻌﺎﺑﺮ ﻟﻠﻤﻬﻤﺔ . إن ﻫﺬه اﻟﺘﻘ ﻨﻴـﺔ اﻟﺘـﻲ ﺗﻨﻄﺒـﻖ ﻋـﲆ ﻣﻌﻈـﻢ اﻟﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴﺔ ذات اﻷﻏﻠﻔﺔ اﻟﺠﻮﻳﺔ اﻟﺘـﻲ ﺗﻌﱪ أﻣﺎم ﻧﺠﻤﻬﺎ ﻋﲆ ﻃﻮل ﺧﻂ اﻟﺮؤﻳﺔ ﺗﻘﻮم أﺳﺎﺳﺎ ﻋﲆ ﻃﺮح ﻃﻴﻒ اﻟﻨﺠﻢ ﻋﻨﺪﻣﺎ ﻻ ﻳﻜﻮن اﻟﻜﻮﻛﺐ اﻟﻨﺠﻤﻲ ﰲ ﺣﺎﻟﺔ ﻋﺒﻮر ﻣـﻦ اﻟﻄﻴـﻒ اﻟﺬي ﺗﻢ اﻟﺘﻘﺎﻃﻪ أﺛﻨـﺎء اﻟﻌﺒـﻮر وﻳـﻮﻓﺮ ﻫـﺬا اﻻﺧﺘﻼف ﰲ اﻟﺘﻜﻮﻳﻦ ﻃﺒﻴﻌﺔ اﻟﻐﺎزات ا ﻮﺟﻮ دة ﰲ اﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟ ﻨﺠﻤﻲ . ﻳﱰك ﻫـﺬا ا ـﺮور ﻟﻠﻜﻮﻛـﺐ آﺛـﺎراً ﺧﺎﻓﺘـﺔ ﰲ اﻟﻄﻴﻒ اﻟﻨﺠﻤﻲ واﻟﺘـﻲ ﻳﻤﻜـﻦ ﻟﻠﻤـﺮاﻗﺒ أن ﻳﺘﻌﺮﻓﻮا ﻋﲆ اﻟﻐـﺎزات اﻟﺘـﻲ ﺗﺸـﻜﻞ اﻟﻐـﻼ ف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟﻨﺠﻤﻲ ﺑﺸـﻜﻞ دﻗﻴـﻖ ﻣﻤـﺎ ﻳﻜﺸﻒ ﻋﻦ ﺗﺮﻛﻴﺒﺘـﻪ اﻟﻜﻴﻤﻴﺎﺋﻴـﺔ وﻳﺴـﻬﻢ ﰲ ﻓﻬﻤﻨﺎ ﻟﺒﻴﺌﺎت اﻟﻜﻮاﻛﺐ اﻟ ﻨﺠﻤﻴﺔ . ﻈﻬـــــﺮ ـــــﮫ اﻟﻨﻈـــــﺎم اﻟﻨ ﻤــــﻲ اﻟﻘــــﺰم ـــــﺪو ﻋﻠ ﻫـــــﺬا اﻟﺮﺳــــــﻢ اﻟﺘﺨ ﻠـــــﻲ ﻣـــــﺎ ﻗــــﺪ ﻳ K2-18 وذﻟـــﻚ اﺳـــــﺘﻨﺎداً إﻟـــــﻰ اﻟﺒ ﺎﻧﺎت اﻟﻌﻠﻤ ﺔ . K2-18b ﻫﻮ اﻟ ﻮﻛﺐ اﻟﻤﻮﺟﻮد ﻓﻲ اﻟﻤﻘﺪﻣﺔ ﻋﻠـﻰ اﻟ ﻤـ ﺑ ﻨﻤـﺎ اﻟ ﻮ ﻛـﺐ اﻟﻘـﺰم ﻓـﻲ اﻟـﺨﻠﻔ ﺔ ﻓﻲ أﺳﻔﻞ اﻟ ﺴﺎر . [NASA, CSA, ESA,J. Olmstead (STScI),N.Mad- husudhan (UniversityofCambridge)] ﻣﺎ ﻫﻮ ﺎﻟﻀ ﻂ K2-18 b ؟ ﻻ أﺣﺪ ﻳﻌﺮ ف ﺑﺎﻟﻀﺒﻂ ﻓﺎﻟﻔﺮق ا ﺨﺘﻠﻔﺔ ﻣـﻦ اﻟﺒﺎﺣﺜ اﻟـﺬﻳﻦ درﺳـﻮا اﻟﻜﻮﻛـﺐ ﺣﺘـﻰ اﻵ ن ﺗﻮﺻﻠﻮا إﱃ اﺳﺘﻨﺘﺎﺟﺎت ﻣﺘﻀـﺎرﺑﺔ واﻋﺘﻤـﺎداً ﻋﲆ ﻧﻤﺎذج ا ﻘﺎرﻧﺔ ﺗﺒ أن اﻟﻜﻮﻛﺐ K2-18b ﻫﻮ أرض ﻓﺎﺋﻘﺔ وﻟﻴﺲ ﻧﺒﺘﻮن ﺻﻐ أو ﺷـﺒﻪ ﻧﺒﺘـﻮن وﻳﻮﺟـﺪ ﺣﺎﻟﻴـ ﺎ اﺗﺠـﺎه ﻣﺜـ ﻟﻠﺠـ ل ﺪ ﻟﺘﺼﻨﻴﻔﻪ ﻋﲆ أﻧﻪ ﻛﻮﻛﺐ " ﻫﺎﻳﺸـﻴﺎﻧﻲ " وﻗـﺪ ﺻﺎغ ﻫﺬا ا ﺼﻄﻠﺢ ﻣﻨﺬ ﺣﻮاﱄ أرﺑـﻊ ﺳـﻨﻮات ﻓﺮﻳﻖ ﻣﻦ اﻟﺒﺎﺣﺜ ﺑ ﻘﻴﺎدة اﻟﱪوﻓﻴﺴﻮر ﻧﻴﻜـﻮ ﻣﺎدوﺳﻮدان اﻟﺬي أﻋﻠﻦ ﻋـﻦ اﻛﺘﺸـﺎف ﻣـﺎدة ــــ ﺛﻨﺎﺋﻲ ﻣﻴﺜﻴـﻞ اﻟﻜﱪﻳﺘﻴـﺪ ﰲ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻜﻮﻛﺐ K2-18 " و " ﻫﺎﻳﺸﻴﺎن ﻫﻮ ﻣﺼﻄﻠ ﺢ ﻣﺘﻼ زم ﺑ اﻟﻬﻴﺪروﺟ وا ﺤـﻴﻂ وﻳﺸـ إﱃ ﻛﻮﻛﺐ ﻣﻐﻄﻰ ﻓﻘﻂ ﺑﻤﺤﻴﻂ ﻋﻤﻴﻖ ﺟﺪاً ﻣـﻦ ا ﺎء ﻳﻐﻤﺮه ﻏﻼف ﺟﻮي ﺳﻤﻴﻚ ﻳﺘﻜﻮن أﺳﺎﺳﺎً ﻣﻦ اﻟﻬﻴﺪروﺟ . ﻻ ﻳﻌﺮف ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻋﲆ وﺟﻪ اﻟﻴﻘ ﻣﺎ إذا ﻛﺎﻧﺖ ﻫﺬه اﻟﻌـﻮاﻟﻢ ﻣﻮﺟـﻮدة ﺑﺎﻟﻔﻌـﻞ ﻟﻜـﻦ اﻟﻨﻤﺎذج اﻟﺘﻲ ﺗﺼـﻔﻬﺎ ﺗﺘﻨﺎﺳـﺐ ﺟﺰﺋﻴـ ﺎ ﻋـﲆ اﻷﻗﻞ ﻣﻊ ﺣﺎﻟﺔ اﻟﻜﻮ ﻛﺐ K2-18b . ﻳﻮﻟﻴﻮ - ﺃﻏﺴﻄﺲ 2 0 2 5 ﺗﻤﺜﻴـــــــﻞ ﻼﺳـــــــﺘ ﻜﻲ ﻟــــــــﺠﺰ ﺌﺎت ﺛﻨـــــــﺎﺋﻲﻣ ﺜﻴـــــــﻞ ــﺪ اﻟﻜ ﺘ ) DMS ( ﻋﻠــﻰ اﻟ ﺴــﺎرو ﺛﻨــﺎﺋﻲﻣ ﺜﻴــﻞ ﺛﻨﺎﺋﻲ اﻟﻜ ﺘ ﺪ ) DMDS ( ﻋﻠﻰ اﻟ ﻤ [Research Gate]