Free Astronomy Magazine November-December 2023 ARABIC VERSION

be- cause of the extended wavelength range and unprecedented sensitiv- ity of Webb, which enabled robust detection of spectral features with just two transits,” said Madhusud- han. “For comparison, one transit observation with Webb provided comparable precision to eight ob- servations with Hubble conducted planet can support life. The planet’s large size — with a radius 2.6 times the radius of Earth — means that the planet’s interior likely contains a large mantle of high-pressure ice, like Neptune, but with a thinner hy- drogen-rich atmosphere and an ocean surface. Hycean worlds are predicted to have oceans of water. However, it is also possible that the ocean is too hot to be habitable or be liquid. “Although this kind of planet does not exist in our solar system, sub- Neptunes are the most common type of planet known so far in the galaxy,” explained team member Subhajit Sarkar of Cardiff University. “We have obtained the most de- tailed spectrum of a habitable-zone sub-Neptune to date, and this al- lowed us to work out the molecules that exist in its atmosphere.” Characterizing the atmospheres of exoplanets like K2-18 b — meaning identifying their gases and physical conditions — is a very active area in astronomy. However, these planets are outshone — literally — by the glare of their much larger parent stars, which makes exploring exo- planet atmospheres particularly challenging. The team sidestepped this challenge by analyzing light from K2-18 b’s parent star as it passed through the exoplanet’s atmosphere. K2-18 b is a transiting exoplanet, meaning that we can detect a drop in bright- ness as it passes across the face of its host star. This is how the exoplanet was first discovered in 2015 with NASA’s K2 mission. This means that during transits a tiny fraction of starlight will pass through the exo- planet’s atmosphere before reach- ing telescopes like Webb. The starlight’s passage through the exoplanet atmosphere leaves traces that astronomers can piece together to determine the gases of the exo- planet’s atmosphere. over a few years and in a relatively narrow wavelength range.” “These results are the product of just two observations of K2-18 b, with many more on the way,” ex- plained team member Savvas Con- stantinou of the University of Cambridge. “This means our work here is but an early demonstration of what Webb can observe in habit- able-zone exoplanets.” The team now intends to conduct follow-up research with the tele- scope’s MIRI (Mid-Infrared Instru- ment) spectrograph that they hope will further validate their findings and provide new insights into the environmental conditions on K2-18 b. “Our ultimate goal is the identifi- cation of life on a habitable exo- planet, which would transform our understanding of our place in the universe,” concluded Madhusudhan. “Our findings are a promising step towards a deeper understanding of Hycean worlds in this quest.”  اﻟﺤﺠﻢ اﻟﻜﺒ ﻟﻠﻜﻮﻛﺐ - ﺣﻴﺚ ﻳﺒﻠﻎ ﻧﺼـﻒ ﻗﻄﺮه 2.6 ﻣﺮة ﻧﺼﻒ ﻗﻄﺮ اﻷرض - ﻳﻌﻨـﻲ أن ﺑﺎﻃﻦ اﻟﻜﻮﻛﺐ ﻣﻦ ا ﺤﺘﻤـﻞ أن ﻳﺤﺘـﻮي ﻃﺒﻘﺔ ﻋﲆ ﻛﺒ ة ﻣﻦ اﻟﺠﻠﻴﺪ ﻋـﺎﱄ اﻟﻀـﻐﻂ ﻣﺜﻞ ﻧﺒﺘﻮن، وﻟﻜـﻦ ﻣـﻊ ﻏـﻼف ﺟـﻮي أرق وﻏﻨـﻲ ﺑﺎﻟﻬﻴ ـﺪروﺟ وﺳـﻄﺢ ﻣﺤﻴﻄـﻲ . ﻳﺘﻮﻗﻊ أن ﺗﺤﺘـﻮي ﻋـﻮاﻟﻢ ﻫﻴﺴـﻴﺎن ﻋـﲆ ﻣﺤﻴﻄﺎت ﻣﻦ ا ﺎء وﻣﻊ ذﻟﻚ ﻓﻤـﻦ ا ﻤﻜـﻦ أﻳﻀًﺎ أن ﻳﻜﻮن ا ﺤﻴﻂ ﺳﺎﺧﻨ ﺑ اً ﺟﺪ ﺎً ﺤﻴﺚ ﻻ ﻳﻤﻜﻦ أن ﻳﻜﻮن ﺻﺎﻟﺤﺎً ﻠﺤﻴﺎة ﻟ أو ﺳﺎﺋﻼً . أوﺿﺢ ﻋﻀﻮ اﻟﻔﺮﻳﻖ ﺳﻮﺑﻬﺎﺟﻴﺖ ﺳـﺎرﻛﺎر ﻣﻦ ﺟﺎﻣﻌﺔ ﻛﺎردﻳﻒ " : ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ ﻋـﺪم وﺟﻮد ﻫﺬا اﻟ ﻨﻮع ﻣـﻦ اﻟﻜﻮاﻛـﺐ ﰲ ﻧﻈﺎﻣﻨـﺎ اﻟﺸﻤﴘ إﻻ أن اﻟﻜﻮ ﻛﺐ اﻟﺸـﺒﻴﻬﺔ ﺑﻜﻮﻛـﺐ ﻧﺒﺘﻮن ﻫﻲ اﻟﻨﻮع اﻷﻛﺜﺮ ﺷﻴﻮﻋ ﺎً ﻣﻦ اﻟﻜﻮاﻛﺐ ا ﻌﺮوﻓﺔ ﺣﺘﻰ اﻵن ﰲ ا ﺠﺮة . ﻟﻘﺪ ﺣﺼﻠﻨ ﺎ ﻋـﲆ اﻟﻄﻴـﻒ اﻷﻛﺜـﺮ ﺗﻔﺼـﻴﻼً ﻟﻠﻤﻨﻄﻘﺔ اﻟﻔﺮﻋ ﻴﺔ ﻷﺷﺒﺎه ﻧﺒﺘﻮن اﻟﺼـﺎﻟﺤﺔ ﺤﻴﺎة ﻟﻠ ﺣﺘﻰ اﻵن وﻫﺬا ﺳﻤﺢ ﺑﺎﻟﺘﻌﺮف ﻋـﲆ اﻟﺠﺰﻳﺌﺎت ا ﻮﺟﻮدة ﰲ ﻏﻼﻓﻪ اﻟﺠﻮي ." ﻳﻌﺘﱪ ﺗﻮﺻﻴﻒ اﻷﻏﻠﻔﺔ اﻟﺠﻮﻳﺔ ﻟﻠﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴـﺔ ﻣﺜﻞ K2-18 b - ﻣﻤﺎ ﻳﻌﻨﻲ ﺗﺤﺪﻳﺪ ﻏﺎزاﺗﻬـﺎ اﻟﺠﻮﻳﺔ ﻟﻠﻜﻮاﻛـﺐ اﻟﺨﺎرﺟﻴـﺔ أﻣـﺮًا ﺻـﻌﺒًﺎ ﻣﺜ ﻞ اﻟﻜﻮﻛﺐ K2-18 b ﻣـﺎ ﻳﻌﻨـﻲ ﺗﺤﺪﻳـﺪ ﻏﺎزاﺗﻬﺎ وﻇﺮوﻓﻬﺎ اﻟﻔﻴﺰﻳﺎﺋﻴﺔ ﺠﺎﻻً ﻣ - ﻧﺸﻄﺎً ﻟﻠﻐﺎﻳﺔ ﰲ ﻋﻠﻢ اﻟﻔﻠﻚ وﻣـﻊ ذﻟـﻚ ﻓـﺈ ن ﻫـﺬه اﻟﻜﻮاﻛـﺐ ﺗﺘﻔـﻮق - ﻋـ - ﺎً ﺣﺮﻓﻴـ ﲆ وﻫــﺞ ﻧﺠﻮﻣﻬـﺎ اﻷم اﻷﻛـﱪ ﺣﺠﻤـﺎً ﻣﻤــﺎ ﻳﺠﻌـﻞ اﺳﺘﻜﺸــﺎف اﻷﻏ ﻠﻔــﺔ اﻟﺠﻮﻳــﺔ ﻟﻠﻜﻮاﻛــﺐ اﻟﺨﺎرﺟﻴﺔ أﻣﺮ اً ﺎً ﺻﻌﺒ ﺑﺸـﻜﻞ ﺧـﺎص . ﻘـﺪ ﻟ ﺗﺠﻨﺐ اﻟﻔﺮﻳﻖ ﻫﺬا اﻟﺘﺤﺪي ﻣﻦ ﺧﻼل ﺗﺤﻠﻴﻞ اﻟﻀﻮء اﻟﺼﺎدر ﻣﻦ اﻟﻨﺠﻢ اﻷم ﻟــ K2-18 b أﺛﻨﺎء ﻣﺮوره ﻋﱪ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻜﻮﻛـﺐ اﻟﺨﺎرﺟ ﻲ K2-18 b و ﻫـﻮ ﻛﻮﻛـﺐ ﻧﺠﻤـﻲ ﻋﺎﺑﺮ ﻣ ﺎ ﻳﻌﻨﻲ أﻧﻪ ﻳﻤﻜﻨﻨﺎ اﻛﺘﺸﺎف اﻧﺨﻔﺎض ﰲ اﻟﺴــﻄﻮع أﺛﻨــﺎء ﻣــﺮوره أﻣــﺎم ﻧﺠﻤ ـﻪ ا ﻀـﻴﻒ . ﺑﻬ ـﺬه اﻟﻄﺮﻳﻘ ـﺔ ﺗــﻢ اﻛﺘﺸــﺎف اﻟﻜﻮﻛﺐ اﻟﻨﺠﻤﻲ ﻷول ﻣﺮة ﰲ ﻋﺎم 2015 ﻣﻦ ﺧﻼل ﻣﻬﻤﺔ K2 اﻟﺘﺎﺑﻌﺔ ﻟﻨﺎﺳﺎ وﻫﺬا ﻳﻌﻨـﻲ أﻧﻪ أﺛﻨﺎء اﻟﻌﺒﻮر ﺳﻴﻤﺮ ﺟﺰء ﺻﻐ ﻣﻦ ﺿﻮء اﻟﻨﺠ ﻢ ﻋﱪ اﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟﻨﺠﻤـﻲ ﻗﺒﻞ أن ﻳﺼﻞ إﱃ اﻟﺘﻠﺴﻜﻮﺑﺎت ﻣﺜﻞ وﻳﺐ . ﻳﱰك ﻣﺮور ﺿﻮء اﻟﻨﺠـﻮم ﻋـﱪ ا ﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻜﻮﻛﺐ اﻟﺨﺎرﺟﻲ آﺛﺎر اً ﻳﻤﻜﻦ ﻟﻌﻠﻤﺎء اﻟﻔﻠﻚ ﺗﺠﻤﻴﻌﻬﺎ ﻣﻌًﺎ ﻟﺘﺤﺪﻳﺪ اﻟﻐﺎزات ا ﻮﺟـﻮدة ﰲ اﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟﺨﺎرﺟﻲ .. ﺗﺠﻤﻴﻌﻬﺎ ﻣﻌ ﺎً ﻟﺘﺤﺪﻳﺪ اﻟﻐﺎزات ا ﻮﺟـﻮدة ﰲ اﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟﺨﺎرﺟﻲ . ﻗﺎل ﻣﺎدﻫﻮﺳﻮدان " : ﻟﻢ ﺗﻜﻦ ﻫﺬه اﻟﻨﺘﻴﺠـﺔ ﻣﻤﻜﻨﺔ إﻻ ﺑﺴـﺒﺐ ﻧﻄـﺎق اﻟﻄـﻮل ا ـﻮﺟﻲ ا ﻤﺘﺪ واﻟﺤﺴﺎﺳﻴﺔ ﻟ ﺘﻠﺴﻜﻮب وﻳـﺐ واﻟﺘـﻲ ﻣﻜﻨﺖ ﻣﻦ اﻟﻜﺸـﻒ اﻟﻘـﻮي ﻋـﻦ اﻟﺴـﻤﺎت اﻟﻄﻴﻔﻴـﺔ ﻣـﻦ ﺧـﻼل ﻋﺒـﻮرﻳﻦ ﻓﻘـﻂ ." ﻟﻠﻤﻘﺎرﻧﺔ ﻗﺪﻣﺖ إﺣﺪى ﻋﻤﻠﻴﺎت رﺻﺪ اﻟﻌﺒﻮر اﻟﺘﻲ أﺟﺮاﻫﺎ ﺗﻠﺴﻜﻮب وﻳـﺐ دﻗـﺔ ﻣﻤﺎﺛﻠـﺔ ﻟﺜﻤﺎﻧﻲ ﻋﻤﻠﻴـﺎت رﺻـﺪ أﺟﺮاﻫـﺎ ﺗﻠﺴـﻜﻮب ﻫﺎﺑﻞ ﻋﲆ ﻣﺪى ﺑﻀـﻊ ﺳـﻨﻮ ات وﰲ ﻧﻄـﺎق ﻃﻮل ﻣﻮﺟﻲ ﺿﻴﻖ ﻧﺴـﺒﻴﺎً . أوﺿـﺢ ﻋﻀـﻮ اﻟﻔﺮﻳﻖ ﺳﺎﻓﺎس ﻛﻮﻧﺴﺘﺎﻧﺘﻴﻨﻮ ﻣـﻦ ﺟﺎﻣﻌـﺔ ﻛﺎﻣﱪﻳﺪج " : ﻫﺬه اﻟﻨﺘﺎﺋﺞ ﻫﻲ ﻧﺘﺎج رﺻـﺪﻳﻦ ﻓﻘﻂ ﻟ ﻠﻜﻮﻛـﺐ K2-18 b وﻫﻨـﺎك ا ﺰﻳـﺪ ﰲ اﻟﻄﺮﻳﻖ وﻫﺬا ﻳﻌﻨﻲ أن ﻋﻤﻠﻨـﺎ ﻟـﻴﺲﺳـﻮى ﻋﺮض ﻣﺒﻜﺮ ﻟﻘﺪرة ﺗﻠﺴﻜﻮب وﻳﺐ ﰲ رﺻﺪ اﻟﻜﻮاﻛـﺐ اﻟﻨﺠﻤﻴـﺔ ﰲ ا ﻨﻄﻘـﺔ اﻟﺼــﺎﻟﺤ ﺔ ﻟﻠﺤﻴﺎة . ﻳﻌﺘـﺰم اﻟﻔﺮﻳـﻖ اﻵن إﺟـﺮاء ﺑﺤـﺚ ﻣﺘﺎﺑﻌﺔ ﺑﺎﺳﺘﺨﺪام ﻣﻘﻴﺎس اﻟﻄﻴﻒ " ﻣ ي " ﻟ ﻸﺷﻌﺔ ﺗﺤﺖ اﻟ ﺤﻤﺮاء ا ﺘﻮﺳﻄﺔ ( اﻟﺨـﺎص ﺑﺎﻟﺘﻠﺴﻜﻮب وﻳﺄﻣﻠﻮن اﻟﺘﺤﻘﻖ ﻣﻦ ﻧﺘﺎﺋﺠﻬﻢ وﺗﻘﺪﻳﻢ رؤى ﺟﺪﻳﺪة ﺣﻮل اﻟﻈﺮوف اﻟﺒﻴﺌﻴـﺔ ﻋ ـﲆ K2-18b . ﺧﻠــﺺ ﻣﺎدﻫﻮﺳـﻮدان إﱃ اﻟﻘﻮل " : إن ﻫﺪﻓﻨﺎ اﻟﻨﻬﺎﺋﻲ ﻫﻮ ﺗﺤﺪﻳﺪ اﻟﺤﻴﺎة ﻋﲆ ﻛﻮﻛﺐ ﻧﺠﻤﻲ ﻟﻠﺤﻴﺎة ﺻﺎﻟﺢ اﻷﻣﺮ اﻟﺬي ﻣﻦ ﺷﺄﻧﻪ أن ﻳﻐ ﻓﻬﻤﻨﺎ ﻜﺎﻧﻨﺎ ﰲ اﻟﻜﻮن ." إن اﻟﻨﺘﺎﺋﺞ اﻟﺠﺪﻳﺪة ﻫﻲ ﺧﻄﻮة واﻋﺪة ﻔﻬﻢ ﻟ أﻋ ﻤﻖ ﻟﻌﻮاﻟﻢ ﻫﻴﺴﻴﺎن ﰲ ﻫﺬا ا ﺴﻌﻰ . ﻧﻮﻓﻤﺒﺮ - ﺩﻳﺴﻤﺒﺮ 2 0 2 3 ـــﺎف ﺗﻌـــﺮضأﻃ K2-18 b ﺗـــﻢ اﻟــــﺤﺼﻮلﻋﻠﻴﻬـــﺎ ﺎﺳــﺘﺨﺪام اﻟـــ NIRISS ﺗﺼـــﻮﻳﺮاﻷﺷــﻌﺔ ﺗﺤـــﺖ ـﻒ ـﺔ وﻣﺮﺳـﻢ اﻟﻄ اﻟــ ﻤﺮاء اﻟﻘﺮ ) ـﺪونﺷـﻖ ﻣــﻦ( ﺗﻠﺴـ ﻮب ـﺐ و و NIRSpec ـﺎفاﻷﺷــﻌﺔ ﻣﻄ ﺗﺤــــﺖاﻟـــــ ـ ــــﺔ ﻤﺮاء اﻟﻘﺮ ( وﻓــــﺮة اﻟﻤ ﺜـــــﺎن وﺛـــــﺎﻧﻲأﻛﺴــــ ﺪ اﻟﻜﺮ ــــﻮن ﻓــــﻲاﻟﻐــــﻼفاﻟـــــﺠﻮيﻟﻠ ﻮﻛــــﺐ ـــﺪ اﻟﻨ ﻤـــﻲ، ﺎﻹﺿـــﺎﻓﺔ إﻟــــﻰاﺣﺘﻤـــﺎل اﻛﺘﺸـــﺎفﺟــــﺰيء ﺴـــﻤﻰﺛﻨـــﺎﺋﻲﻣ ﺜﻴــــﻞ ﻛ ﺘ . إن اﻛﺘﺸــــﺎف ـــــﺎ ﺘﻮاﻓــــــﻖﻣـــــﻊ وﺟــــــﻮد ﻣﺤـــــ ﻂﺗﺤــــــﺖﺟــــــﻮﻏــــــ اﻟﻤ ﺜـــــﺎن وﺛــــــﺎﻧﻲأﻛﺴـــــ ﺪ اﻟﻜﺮ ـــــﻮن وﻧﻘـــــﺺاﻷﻣﻮﻧ ﻓـــﻲاﻟ ﻮﻛـــﺐ ـــﺪروﺟ ﺎﻟﻬ K2-18b ﺗ ﻠـــﻎ اﻟـــﺬ ﻛﺘﻠﺘـــﮫ 8.6 ــﺪورﺣـــﻮل اﻟـــﻨ ﻢ ﻣـــﺮة ﻛﺘﻠـــﺔ اﻷرضو اﻟﻘﺰم اﻟ ﺎرد K2-18 ﻓﻲاﻟﻤﻨﻄﻘﺔ اﻟﺼﺎﻟـﺤﺔ ﻟﻠﺤ ﺎة و ﻘﻊﻋﻠﻰ ﻌﺪ 110 ﺳﻨﺔﺿﻮﺋ ﺔ ﻣﻦ اﻷرض .