Free Astronomy Magazine March-April 2024 ARABIC VERSION

some point, as we study smaller planets, there must be a transition where there’s no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide).” Because the planet is as hot as Venus at roughly 425 degrees Celcius, it definitely would be an inhospitable, steamy world if the atmosphere were predominantly water vapour. At present the team is left with two possibilities. The planet is still cling- ing to a hydrogen-rich envelope laced with water, making it a mini- Neptune. Alternatively, it could be a warmer version of Jupiter’s moon Europa, which has twice as much water as Earth beneath its crust. “The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapour on top of some smaller rocky body,” said Benneke. If the planet has a residual water- rich atmosphere, then it must have formed farther away from its host star, where the temperature is cold and water is available in the form of ice, than its present location. In this scenario, the planet would have then migrated closer to the star and received more radiation. The hydro- gen was then heated and escaped, or is still in the process of escaping, the planet’s weak gravity. The alter- native theory is that the planet formed close to the hot star, with a trace of water in its atmosphere. The Hubble programme observed the planet during 11 transits — events in which the planet crossed in front of its star — that were spaced out over three years. During transits, starlight is filtered through the planet’s atmosphere and carries the spectral fingerprint of water molecules. If there are clouds on the planet, they are low enough in the atmosphere that they don’t com- pletely hide Hubble’s view of the at- mosphere, and Hubble is able to probe water vapour above the clouds. Hubble’s discovery opens the door to studying the planet in more de- tail. It’s a good target for the NASA/ESA/CSA James Webb Space Telescope to do infrared spec- troscopy to look for other atmos- pheric molecules. GJ 9827d was discovered by NASA’s Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.     رﺳــﻢ ﺗﺨ ﻠــﻲ ﻟﻠ ﻮﻛــﺐ اﻟ ﻨ ﻤــﻲ GJ 9827d وﻫــﻮ أﺻــﻐﺮ ﻮﻛــﺐ ﻧ ﻤــﻲ ﺗــﻢ اﻛﺘﺸــﺎف ﺑﺨــﺎراﻟﻤــﺎء ﻓــﻲ ـ ﻏﻼﻓﮫ اﻟ . ﺠﻮي ﻤﻜﻦ أن ﻳ ﻮن اﻟ ﻮﻛﺐ ﻣﺜﺎﻻً ﻋﻠﻰ ـﺎﻩ ﻓـ ـﺔ ﺎﻟﻤ اﻟ ﻮاﻛـﺐ اﻟﻤﺤﺘﻤﻠـﺔ ذات اﻷﺟـﻮاء اﻟﻐﻨ ﻲ أﻣــﺎﻛﻦ أﺧــﺮىﻣــﻦ ﻣﺠﺮﻨـﺎ . إﻧــﮫ ﻮﻛــﺐ ﺻــﺨﺮيﻳ ﻠــﻎ ﻗﻄــﺮﻩ ﺿــﻌﻒﻗﻄــﺮاﻷرضﻓﻘــﻂ ــﺪورﺣــﻮل اﻟــﻨ ﻢ و اﻟﻘﺰم اﻷ ﻤﺮ GJ 9827 وﻳﻮﺟﺪ ﻮﻛ ﺎن داﺧﻠ ﺎن ﻓﻲ اﻟﻨﻈﺎم ﻋﻠﻰ اﻟ ﺴﺎر . ﺗـﻢ رﺳـﻢ ﻧﺠـﻮم اﻟـ ـ ﺨﻠﻔ ﺔ ﻤـﺎ اﻟﻤﺠﺮدة ﻋﻨﺪ اﻟﻨﻈﺮإﻟﻰ ﻤﻜﻦ رؤ ﺘﻬﺎ ﺎﻟﻌ اﻟﻮراء ﻧﺤﻮ اﻟﺸﻤﺲ ﻫﻲﻓﻲﺣﺪ ذاﺗﻬﺎ ﺧﺎﻓﺘﺔ ﺟـﺪ واﻟ اً ـــﺚﻻ ﻤﻜـــﻦ رؤ ﺘﻬـــﺎ ﺑﺤ . ﻫـــﻮ اﻟـــﻨ ﻢ اﻷزرق ﻓـــﻲ أﻋﻠـــﻰ اﻟ ﻤـــ اﻟـــﻨ ﻢ ﻗﻠـــﺐ اﻷﺳـــﺪ ، واﻟـــﻨ ﻢ اﻷﺻـــﻔﺮﻓـــﻲ أﺳــﻔﻞ اﻟﻮﺳــﻂﻫــﻮ اﻟــﻨ ﻢ ذﻳــﻞ اﻷﺳــﺪ ﻫـﻮ اﻟﺴــﻤﺎك واﻟــﻨ ﻢ اﻷزرق ﻓــﻲ أﺳــﻔﻞ اﻟ ﻤــ اﻷﻋــﺰل . ــﺔ ﻮﻛ اﻷﺳـــﺪ ﻋﻠـــﻰ اﻟ ﺴـــﺎر ـــﺔ اﻟﻌـــﺬراء ﻋ و ﻮﻛ ﻠـــﻰ اﻟ ﻤـــ . ﻣﺸـــﻮﻫﺘﺎن ﻣـــﻦ ـــﻮﻛ ﺘ ﻠﺘـــﺎ اﻟ ﻣﻨﻈﻮرـــﺎ اﻟﻤـــﺮ ﻂ ﺎﻷرضﻣﻦ ﻣﺴﺎﻓﺔ 97 . ﺳﻨﺔ ﺿﻮﺋ ﺔ ﻗﺎل ﺑﻴﻨﻴﻜﻲ : ﰲ ﻣﺮﺣﻠﺔ ﻣـﺎ، ﺑﻴﻨﻤـﺎ ﻧـﺪرس اﻟﻜﻮاﻛﺐ اﻟﺼﻐ ة ﻳﺠـﺐ أن ﻳﻜـﻮن ﻫﻨـﺎك ﺗﺤﻮل ﺣﻴﺚ ﻻ ﻳﻮﺟﺪ ا ﺰﻳﺪ ﻣﻦ اﻟ ﻬﻴـﺪروﺟ ﰲ ﻫﺬه اﻟﻌ ﻮاﻟﻢ اﻟﺼﻐ ة وﻟﻬﺎ ﻏـﻼف ﺟـﻮي أﺷﺒﻪ ﺑﻜﻮﻛﺐ اﻟﺰﻫﺮة ) اﻟـﺬي ﻳﻬـﻴﻤﻦ ﻋﻠﻴـﻪ ﺛﺎﻧﻲ أﻛﺴﻴﺪ اﻟﻜﺮﺑﻮن (" . اً ﻧﻈﺮ ﻷن اﻟﻜﻮﻛـﺐ ﺳﺎﺧﻦ ﻣﺜﻞ ﻛﻮﻛﺐ اﻟﺰﻫﺮة ﻋﻨﺪ درﺟﺔ ﺣﺮارة 425 درﺟﺔ ﻣﺌﻮﻳﺔ ﺗﻘﺮﻳﺒ ﺎً ﻓﻤﻦ ا ﺆﻛـﺪ أﻧـﻪ ﻮن ﺳـﻴﻜ ﻛﻮﻛﺒـﺎً ﻏـ ﻣﻀـﻴﺎف وﻣﺸـﺒﻊ ﺑﺎﻟﺒﺨﺎر إذا ﻛﺎن اﻟﻐﻼف اﻟﺠـﻮي ﰲ اﻟﻐﺎﻟـﺐ ﻋﺒﺎرة ﻋﻦ ﺑﺨـﺎر ا ـ .ﺎء ﰲ اﻟﻮﻗـﺖ اﻟﺤـﺎﴐ ﻳﺒﻘـﻰ اﻟﻔﺮﻳـﻖ أﻣـﺎم اﺣﺘﻤـﺎﻟ وﻻ ﻳــﺰال اﻟﻜﻮﻛﺐ ﻣﺘﻤﺴﻜًﺎ ﺑﻐﻼ ف ﻏﻨﻲ ﺑﺎﻟﻬﻴﺪروﺟ وﻣﻤﻠﻮء ﺑﺎ ﺎء ﻣﻤﺎ ﻳﺠﻌﻠـﻪ ﻧﺒﺘﻮﻧـ ﺎً اً ﺻـﻐ وﺑﺪﻻً ﻣﻦ ذﻟﻚ ﻳﻤﻜﻦ أن ﻳﻜﻮن ﻧﺴﺨﺔ أﻛﺜـﺮ دﻓﺌًﺎ ﻣـﻦ ﻗﻤـﺮ ا ﺸـﱰي " ﻳﻮروﺑـﺎ " اﻟـﺬي ﻳﺤﺘﻮي ﻋﲆ ﺿﻌﻒ ﻛﻤﻴﺔ ا ﻴﺎه ا ﻮﺟﻮدة ﻋﲆ اﻷرض ﺗﺤﺖ ﻗﴩﺗﻪ . اﻟﻜﻮﻛـﺐ GJ 9827d ﻳﻤﻜﻦ أن ﻳﻜﻮن ﻧﺼﻔﻪ ﻣﺎء وﻧﺼـﻔﻪ اﻵﺧـﺮ ي ﺻﺨﺮ ﺳﻴﻜﻮن ﻫﻨﺎك اﻟﻜﺜ ﻣﻦ ﺑﺨﺎر ا ﺎء ﻓﻮق ﺟﺴﻢ ﺻﺨﺮي أﺻﻐﺮ ، إذا ﻛﺎن ﻟﻠﻜﻮﻛﺐ ﻏﻼف ﺟﻮي ﻣﺘﺒﻘﻲ ﻏﻨﻲ ﺑﺎ ﻴﺎ ه ﻓﻼ ﺑـﺪ أﻧـ ﻪ ﻗﺪ ﺗﺸﻜﻞ ﺑﻌﻴﺪًا ﻋﻦ ﻧﺠﻤـﻪ ا ﻀـﻴﻒ ﺣﻴـﺚ ﺗﻜﻮن درﺟﺔ اﻟﺤﺮارة ﺑﺎردة وﻳﺘﻮﻓﺮ ا ﺎء ﻋﲆ ﺷﻜﻞ ﺟﻠﻴﺪ ﻣﻘﺎرﻧﺔ ﺑﻤﻮﻗﻌﻪ اﻟﺤﺎﱄ ، ﰲ ﻫـﺬا اﻟﺴﻴﻨﺎرﻳﻮ ﻳﻜﻮن اﻟﻜﻮﻛﺐ ﻗﺪ ﻫﺎﺟﺮ ﺑﺎﻟﻘﺮب ﻣ ﻦ اﻟﻨﺠﻢ وﺗﻠﻘﻰ ا ﺰﻳﺪ ﻣﻦ اﻹﺷﻌﺎع ﺛﻢ ﺗـﻢ ﺗﺴﺨ اﻟﻬﻴﺪروﺟ ﺛﻢ ﻫﺮب أو ﻻ ﻳـﺰال ﰲ ﻃـﻮر اﻟﻬـﺮوب ﻣـﻦ اﻟﺠﺎذﺑﻴـﺔ اﻟﻀـﻌﻴﻔﺔ ﻟﻠﻜﻮﻛﺐ . اﻟﻨﻈﺮﻳﺔ اﻟﺒﺪﻳﻠﺔ ﻫـﻲ أن اﻟﻜ ﻮﻛـﺐ ﺗﺸﻜﻞ ﺑﺎﻟﻘﺮب ﻣﻦ اﻟﻨﺠﻢ اﻟﺴﺎﺧﻦ ﻣﻊ وﺟﻮد أﺛﺮ ﻟﻠﻤﻴﺎه ﰲ ﻏﻼﻓﻪ اﻟﺠـﻮي . ﻗـﺎم ﺑﺮﻧـﺎﻣﺞ ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﺑﻤﺮاﻗﺒﺔ اﻟﻜﻮﻛﺐ ﺧـﻼل 11 ﻋﻤﻠﻴﺔ ﻋﺒﻮر وﻫﻲ اﻷﺣﺪاث اﻟﺘﻲ ﻋـﱪ ﻓﻴﻬـﺎ ـــ اﻟﻜﻮﻛﺐ أﻣﺎم ﻧﺠﻤﻪ و ﻛﺎﻧﺖ ﻣﺘﺒﺎﻋـﺪة ﻋـﲆ ﻣﺪى ﺛﻼث ﺳﻨﻮات . أﺛﻨﺎء اﻟﻌﺒﻮر ﻳـﺘﻢ ﻓﻠـﱰة ﺠ ﺿﻮء اﻟﻨ ﻢ ﻋﱪ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻜﻮﻛـﺐ وﻳﺤﻤﻞ اﻟﺒﺼﻤﺔ اﻟﻄﻴﻔﻴﺔ ﻟﺠﺰﻳﺌﺎت ا ﺎء إذا . ﻛﺎﻧـﺖ ﻫﻨـﺎك ﻏﻴـﻮم ﻋــﲆ اﻟﻜﻮﻛـﺐ ﻓﻬـﻲ ﻣﻨﺨﻔﻀﺔ ﰲ اﻟﻐﻼف اﻟﺠﻮي ﺑﺤﻴﺚ ﻻ ﺗﺨﻔﻲ ﺎً ﺗﻤﺎﻣ رؤﻳﺔ ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﻟﻠﻐﻼف اﻟﺠـﻮي ﻳﺴﺘﻄ و ﻴﻊ ﺳﱪ ﺑﺨﺎر ا ـﺎء ﻓـﻮق ا ﻟﻐﻴـﻮم . ﻳﻔﺘﺢ ﻫﺬا اﻻ ﻛﺘﺸﺎف اﻟﺒـﺎب أﻣـﺎم دراﺳـﺔ اﻟﻜﻮﻛﺐ ﺑﺎﻟﺘﻔﺼﻴﻞ ﺑﻮاﺳﻄﺔ ﺗﻠﺴﻜﻮب وﻳﺐ ﻹﺟـﺮاء اﻟﺘﺤﻠﻴـﻞ اﻟﻄﻴﻔـﻲ ﻟﻸﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء ﻟﻠﺒﺤﺚ ﻋﻦ ﺟﺰﻳﺌﺎت اﻟﻐﻼف اﻟﺠﻮي اﻷﺧﺮى . ﺗﻢ اﻛﺘﺸﺎف GJ 9827d ﺑﻮاﺳـﻄﺔ ﺗﻠﺴﻜﻮب ﻛﻴﺒﻠﺮ اﻟﺘﺎﺑﻊ ﻟﻨﺎﺳﺎ ﰲ ﻋـﺎم 2017 وﻳﻜﻤﻞ دورﺗﻪ ﺣﻮل ﻧﺠﻢ ﻗﺰم أﺣﻤﺮ ﻛﻞ 6.2 ﻳﻮﻣﺎً ﻳﻘﻊ اﻟﻨﺠﻢ GJ 9827 ﻋﲆ ﺑﻌﺪ 97 ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﻣﻦ اﻷرضﰲ ﻛﻮﻛﺒﺔ اﻟﺤﻮت . - ﻣﺎﺭﺱ ﺃﺑﺮﻳﻞ 2 0 2 4