Free Astronomy Magazine March-April 2024 ARABIC VERSION

A 26 Hubble observes a changing exoplanet atmosphere by NASA/ESA − Bethany Downer n international team of as- tronomers has assembled and reprocessed observa- tions of the exoplanet WASP-121 b that were collected with the NASA/ESA Hubble Space Telescope in the years 2016, 2018 and 2019. This provided them with a unique dataset that allowed them not only to analyse the atmosphere of WASP 121 b, but also to compare the state of the exoplanet’s atmosphere across several years. They found clear evidence that the observations of WASP-121 b were varying in time. The team then used sophisti- cated modelling techniques to demonstrate that these temporal variations could be explained by weather patterns in the exoplanet’s atmosphere. WASP-121 b (also known as Tylos) is a well-studied hot Jupiter that or- bits a star that lies about 880 light- years from Earth, completing a full orbit in a very brisk 30-hour period. Its extremely close proximity to its host star means that it is tidally locked, and that the star-facing hemisphere is very hot, with tem- peratures exceeding 3000 Kelvins. The team combined four sets of archival observations of WASP-121 b, all made using Hubble’s Wide Field Camera 3 (WFC 3). The com- plete assembled dataset included observations of: WASP-121 b transit- ing in front of its star (taken in June 2016); WASP-121 b transiting be- hind its star, also known as a sec- ondary eclipse (taken in November 2016); and two phase-curves of WASP-121 b (taken in March 2018 and February 2019 respectively). The team took the unique step of pro- cessing each dataset in the same way, even if it had been previously processed by a different team. Exoplanet data processing is time consuming and complicated, but nonetheless it was worth it because it allowed the team to directly com- pare the processed data from each set of observations with one an- other. One of the principal investiga- tors of the team, Quentin Changeat, an ESA Research Fellow at the Space Telescope Science Institute, elabo- rates: “Our dataset represents a sig- nificant amount of observing time for a single planet and is currently the only consistent set of such re- peated observations. The informa- tion that we extracted from those observations was used to charac- terise (infer the chemistry, temper- ature, and clouds) of the atmos- phere of WASP-121 b at different times. This provided us with an ex- quisite picture of the planet, chang- ing in time.” After cleaning each dataset, the team found clear evidence that the observations of WASP-121 b were varying in time. While instrumen- tal effects could remain, the data showed an apparent shift in the ex- oplanet’s hot spot and differences in MARCH-APRIL 2024 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ ﻳﺮﺻﺪ " ﻫﺎﺑﻞ " ﺗﻐ اتﻓﻲ اﻟﻐﻼف اﻟ ـ ﺠﻮيﻟ ﻮﻛﺐ ﻧ ﻤﻲ : ﻘﻠﻢ ﺜﺎﻧﻲداوﻧﺮ و ﺎﻟﺔ ﻧﺎﺳﺎ / و ﺎﻟﺔ اﻟﻔﻀﺎء اﻷوروﺑ ﺔ ﻗـﺎم ﻓﺮﻳﻖ دوﱄ ﻣﻦ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﺑﺘﺠﻤﻴـﻊ وإﻋﺎدة ﻣﻌﺎﻟﺠﺔ أرﺻـﺎد اﻟﻜﻮﻛـﺐ اﻟﻨﺠﻤـﻲ WASP-121 b اﻟﺘﻲ ﺗﻢ ﺟﻤﻌﻬﺎ ﺑﺎﺳـﺘﺨﺪام ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ اﻟﻔﻀﺎﺋﻲ اﻟﺘﺎﺑﻊ ﻟ ﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ ووﻛﺎﻟﺔ اﻟﻔﻀﺎء اﻷوروﺑﻴﺔ ﰲ اﻷﻋـﻮام 2016 و 2018 و 2019 وﻗـــﺪ زودﻫـــﻢ ذﻟـــﻚ ﺑﻤﺠﻤﻮﻋﺔ ﺑﻴﺎﻧﺎت ﻣﻬﻤﺔ ﺳﻤﺤﺖ ﻟﻬﻢ ﻟـﻴﺲ ﻓﻘـﻂ ﺑﺘﺤﻠﻴــﻞ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻜﻮﻛـﺐ WASP 121 b وﻟﻜﻦ أﻳﻀًﺎ ﺑﻤﻘﺎرﻧـﺔ ﺣﺎﻟـﺔ اﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ اﻟ ﻨﺠﻤﻲ ﻋـﲆ ﻣـﺪار ﻋﺪة ﺳﻨﻮات و وﺟﺪوا دﻟﻴﻼً واﺿﺤ ﺎ ﻋـﲆ أن أرﺻــﺎد اﻟﻜﻮﻛــﺐ WASP-121 b ﻛﺎﻧــﺖ ﺗﺨﺘﻠﻒ ﺑﻤﺮور اﻟﻮﻗﺖ . ﺛﻢ اﺳﺘﺨﺪم اﻟﻔﺮﻳـﻖ ﺗﻘﻨﻴﺎت ﻧﻤﺬﺟﺔ ﻣﺘﻄـﻮرة ﻹﺛﺒـﺎت أن ﻫـﺬه اﻻﺧﺘﻼﻓﺎت اﻟﺰﻣﻨﻴﺔ ﻳﻤﻜـﻦ ﺗﻔﺴـ ﻫﺎ ﻣـﻦ ﺧﻼل أﻧﻤـﺎط اﻟﻄﻘـﺲ ﰲ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻜﻮﻛﺐ اﻟ ﻨﺠﻤﻲ . إن WASP-121 b ) ا ﻌـﺮوف أﻳﻀـ ﺎً ﺑﺎﺳـﻢ ﺗﺎﻳﻠﻮس ﻫ( ﻮ ﻛﻮﻛـﺐ ﻣﺸـﱰي ﺣـﺎر ﺗﻤـﺖ دراﺳﺘﻪ ﺟﻴﺪ اً وﻳﺪور ﺣﻮل ﻧﺠﻢ ﻳﺒﻌﺪ ﺣـﻮاﱄ 880 ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﻣﻦ اﻷرض وﻳﻜﻤﻞ ﻣـﺪار اً ﻛﺎﻣﻼً ﰲ ﻓﱰة ﴎﻳﻌﺔ ﺟﺪ اً ﻣﺪﺗﻬﺎ 30 . ﺳﺎﻋﺔ إن ﻗﺮﺑﻪ اﻟﺸﺪﻳﺪ ﻣﻦ ﻧﺠﻤﻪ ا ﻀﻴﻒ ﻳﻌﻨﻲ أﻧﻪ ﻣﻐﻠـﻖ ﻣـﺪﻳًﺎ، وأن ﻧﺼـﻒ اﻟﻜــﺮة اﻷرﺿـﻴﺔ ا ﻮاﺟﻪ ﻟﻠـﻨﺠﻢ ﺣـﺎر ﺟـﺪًا ﺣﻴـﺚ ﺗﺘﺠـﺎوز درﺟﺎت اﻟﺤﺮارة 300 . ﻛﻠﻔﻦ ﺟﻤﻊ اﻟﻔﺮﻳـﻖ أرﺑﻊ ﻣﺠﻤﻮﻋﺎت ﻣـﻦ اﻷرﺻـﺎد اﻷرﺷـﻴﻔﻴﺔ ﻟﻠﻜﻮﻛﺐ WASP-121 b وﻛﻠﻬﺎ ﺗﻢ إﺟﺮاؤﻫﺎ ﺑﺎﺳﺘﺨﺪام ﻛﺎﻣ ا ﺗﻠﺴﻜﻮب ﻫﺎﺑـﻞ واﺳـﻌﺔ ا ﺠﺎل 3 (WFC 3) . ﺗﻀﻤﻨﺖ ﻣﺠﻤﻮﻋﺔ اﻟﺒﻴﺎﻧﺎت اﻟﻜﺎﻣﻠﺔ ا ُﺠﻤﱠ ﻌﺔ أرﺻﺎداً ﺎ ﻳﲇ : ﻋﺒـﻮر WASP-121 b أﻣـﺎم ﻧﺠﻤــﻪ ) ﺗــﻢ اﻟﺘﻘﺎﻃــﻪ ﰲ ﻳﻮﻧﻴــﻮ 2016 ( WASP-121 b ﻳﻤﺮ ﺧﻠﻒ ﻧﺠﻤﻪ ا ﻌـﺮوف أﻳﻀ ﺎً ﺑﺎﺳﻢ اﻟﻜﺴﻮف اﻟﺜﺎﻧﻮي ) ﺗﻢ اﻟﺘﻘﺎﻃـﻪ ﻮﻓﻤﱪ ﰲ ﻧ 2016 ( وﻣﻨﺤﻨﻴـﺎت اﻟﻄـﻮر ﻟــ WASP-121 b ﺗـﻢ اﻟﺘﻘﺎﻃﻬـﺎ ﰲ ﻣـﺎرس 2018 وﻓﱪاﻳﺮ 2019 . ﻋﲆ اﻟﺘﻮاﱄ اﺗﺨﺬ اﻟﻔﺮﻳﻖ اﻟﺨﻄـﻮة اﻟﻔﺮﻳـﺪة ا ﺘﻤﺜﻠـﺔ ﰲ ﻣﻌﺎﻟﺠـﺔ ﻛ ـﻞ ﻣﺠﻤﻮﻋ ـﺔ ﺑﻴﺎﻧ ـﺎت ﺑ ـﻨﻔﺲ اﻟﻄﺮﻳﻘﺔ، ﺣﺘﻰ ﻟﻮ ﺗﻤﺖ ﻣﻌﺎﻟﺠﺘﻬﺎ ﻣﺴـﺒﻘًﺎ ﺑﻮاﺳﻄﺔ ﻓﺮﻳﻖ ﻣﺨﺘﻠﻒ . ﺗﺴﺘﻐﺮق ﻣﻌﺎﻟﺠﺔ ﺑﻴﺎﻧﺎت اﻟﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴﺔ وﻗﺘًﺎ ﻃﻮﻳﻼً وﻣﻌﻘﺪة وﻟﻜﻨﻬﺎ ﻣﻊ ذﻟﻚ ﻛﺎﻧﺖ ذﻟﻚ ﻛﺎﻧﺖ ﺗﺴﺘﺤﻖ اﻟﻌﻨـﺎء ﻷﻧﻬـﺎ ﺳـﻤﺤﺖ ﻟﻠﻔﺮﻳﻖ ﺑﻤﻘﺎرﻧﺔ اﻟﺒﻴﺎﻧﺎت ا ﻌﺎﻟﺠﺔ ﻣﻦ ﻛـﻞ ﻣﺠﻤﻮﻋﺔ ﻣﻦ ا ﻼﺣﻈﺎت ﻣﻊ ﺑﻌﻀﻬﺎ اﻟﺒﻌﺾ ﺑﺸﻜﻞ ﻣﺒﺎﴍ . ﻳﻮﺿﺢ ﻛﻮﻳﻨﺘﻦ ﺗﺸـﺎﻧﺠﺎت، أﺣﺪ اﻟﺒﺎﺣﺜ اﻟﺮﺋﻴﺴـﻴ ﰲ اﻟﻔﺮﻳـﻖ، وﻫـﻮ زﻣﻴﻞ أﺑﺤﺎث ﰲ وﻛﺎﻟﺔ اﻟﻔﻀﺎء اﻷوروﺑﻴـﺔ ﰲ ﻣﻌﻬﺪ ﻋﻠﻮم اﻟﺘﻠﺴﻜﻮب اﻟﻔﻀـﺎﺋﻲ : " ﺗﻤﺜـﻞ ﻣﺠﻤﻮﻋﺔ اﻟﺒﻴﺎﻧﺎت اﻟﺨﺎﺻﺔ ﺑﻨﺎ ﻗـﺪر اً اً ﻛﺒـ ﻣﻦ وﻗﺖ ا ﺮاﻗﺒﺔ ﻟﻜﻮﻛﺐ واﺣﺪ وﻫﻲ ﺣﺎﻟﻴـ ﺎً ا ﺠﻤﻮﻋﺔ اﻟﻮﺣﻴﺪة ا ﺘﺴﻘﺔ ﻣﻦ ﻫﺬه اﻷرﺻﺎد ا ﺘﻜـﺮرة . ﺗـﻢ اﺳـﺘﺨﺪام ا ﻌﻠﻮﻣـﺎت اﻟﺘـﻲ اﺳﺘﺨﺮﺟﻨﺎﻫﺎ ﻣﻦ ﺗﻠـﻚ اﻷرﺻـﺎد ﻟﺘﻮﺻـﻴﻒ ) اﺳــﺘﻨﺘﺎج اﻟﻜﻴﻤﻴــﺎء ودرﺟــﺔ اﻟﺤــﺮارة واﻟﺴﺤﺐ ا( ﻟﻐﻼف اﻟﺠﻮي ﻟﻠﻜﻮﻛﺐ WASP- 121 b ﰲ أوﻗﺎت ﻣﺨﺘﻠﻔﺔ و ﻗـﺪ زودﻧـﺎ ﻫـﺬا ﺑﺼﻮرة راﺋﻌﺔ ﻟﻠﻜﻮﻛﺐ وﻫﻮ ﻳﺘﻐـ ﺑﻤـﺮور اﻟﻮﻗﺖ . ﺑﻌﺪ ﺗﻨﻈﻴﻒ ﻛﻞ ﻣﺠﻤﻮﻋـﺔ ﺑﻴﺎﻧـﺎت، وﺟﺪ اﻟﻔﺮﻳﻖ دﻟﻴﻼً واﺿـﺤًﺎ ﻋـﲆ أن أرﺻـﺎد WASP-121 b ﻛﺎﻧﺖ ﺗﺨﺘﻠﻒ ﺑﻤﺮور اﻟﻮﻗﺖ . ﰲ ﺣ أن اﻟﺘﺄﺛ ات اﻵﻟﻴﺔ ﻗﺪ ﺗﻈﻞ ﻗﺎﺋﻤـﺔ، ﻓﻘﺪ أﻇﻬـﺮت اﻟﺒﻴﺎﻧـﺎت ﺗﺤـﻮﻻً واﺿـﺤًﺎ ﰲ اﻟﻨﻘﻄــﺔ اﻟﺴــﺎﺧﻨﺔ ﻟﻠﻜﻮﻛــﺐ اﻟﻨﺠﻤــﻲ ــــــــ - ﻣﺎﺭﺱ ﺃﺑﺮﻳﻞ 2 0 2 4 26