Free Astronomy Magazine September-October 2024

explain how WASP-107 b can be so inflated without resorting to ex- treme theories of how it formed. The results, which were made pos- sible by Webb’s extraordinary sensi- tivity and accompanying ability to measure light passing through exo- planet atmospheres, may explain thepuffinessofdozensoflow-den- sity exoplanets, helping solve a long-standingmysteryinexoplanet science. At more than three-quar- ters the volume of Jupiter but less than one-tenth the mass, the “warm Neptune” exoplanet WASP- 107bisoneoftheleastdenseplan- ets known. While puffy planets are not uncommon, most are hotter and more massive, and therefore easier to explain. “Based on its radius, mass, age, and assumed internal temperature, we thought WASP-107 b had a very small, rocky core surrounded by a huge mass of hydrogen and he- lium,” explained Luis Welbanksfrom Arizona State University (ASU), lead author on a paper published in Nature . “But it was hard to under- stand how such a small core could sweep up so much gas, and thenstop short of growing fully into a Jupiter- mass planet.” If WASP-107 b instead has more of its mass in the core, the atmosphere should have contracted as the planet cooled over time since it formed. Without a source of heat to re-expand the gas, the planet should be much smaller. Although WASP-107bhasanorbitaldistance ofjust5millionmiles(one-seventh thedistancebetweenMercuryand the Sun), it doesn’t receive enough energy from its star to be so in- flated. “WASP-107 b is such an interesting target for Webb because it’s sig- nificantly cooler and more Nep- tune-like in mass than many of the other low-density planets, the hot Jupiters,we’vebeenstudying,” said David Sing from the Johns Hopkins University (JHU), lead author on a parallel studyalso published in Nature . “As a result, we should be able to detect methane and other molecules that can give us informa- tionaboutitschemistryandinternal dynamics that we can’t get from a hotter planet.” WASP-107 b’s giant radius, ex- tended atmosphere, and edge-on orbitmakeitidealfortransmission spectroscopy, a method used to identifythevariousgasesinanexo- planet atmosphere based on how they affect starlight. Combining observations fromWebb’s NIRCam (Near-Infrared Cam- era), Webb’s MIRI (Mid-Infrared In- strument), and Hubble’s WFC3(Wide Field Camera 3), Welbanks’ teamwasabletobuildabroadspec- trum of 0.8- to 12.2-micron light ab- sorbed by WASP-107 b’s atmos- phere. Using Webb’s NIRSpec (Near- Infrared Spectrograph), Sing’s team built an independent spectrum cov- ering 2.7 to 5.2 microns. The precision of the data makes it possible to not just detect, but ac- tually measure the abundances ofa wealth of molecules, including water vapor (H 2 O), methane (CH 4 ), carbon dioxide (CO 2 ), carbon monoxide(CO),sulfurdioxide(SO 2 ), and ammonia (NH 3 ). Bothspectrashowasurprisingly lack of methane in WASP-107 b’s atmosphere: one-thousandth the amount expected based on its as- sumed temperature. “This is evi- dence that hot gas from deep in the planetmustbemixingvigorously 53 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ ﻳﻮﺿـــﺢ ﻫـــﺬا اﻟﺮﺳـــﻢ اﻟﺘﺨ ﻠـــﻲ ـــﻒ ﻛ ﻤﻜـــﻦ أن ﻳ ــــــــﺪو اﻟ ﻮﻛــــــــﺐ اﻟﻨ ﻤــــــــﻲ WASP-107b ﻨــــــــﺎءً ﻋﻠــﻰ اﻟﺒ ﺎﻧــﺎت اﻟــ ـ ﻤﻌﻬــﺎ ﺗﻠﺴــ ﻮب ﺤﺪ ﺜﺔ اﻟــ ـــــﺐ اﻟﻔﻀـــــﺎﺋﻲ إﻟـــــﻰﺟﺎﻧـــــﺐ ﺟـــــ ﻤﺲو اﻷرﺻـــــﺎد اﻟﺴــــــــﺎ ﻘﺔ ﻣــــــــﻦ ﺗﻠﺴــــــــ ﻮب ﻫﺎﺑــــــــﻞ وﻏــــــــ ﻩ ﻣــــــــﻦ اﻟﺘﻠﺴ ﻮ ﺎت اﻟﻔﻀﺎﺋ ﺔ واﻷرﺿ ﺔ . - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 4 اﻟﻐــﺎزي اﻟﻌﻤــﻼق اﻟــﺪاﻓﺊ WASP-107b ؟ ﻣﺘﻀﺨﻤﺎً اﻟﻨﺘﺎﺋﺞ اﻟﺘﻲ أﺻـﺒﺤﺖ ﻣﻤﻜﻨـﺔ ﺑﻔﻀﻞ ﺣﺴﺎﺳﻴﺔ ﺗﻠﺴﻜﻮب وﻳﺐ اﻻﺳﺘﺜﻨﺎﺋﻴﺔ ﻪ وﻗﺪرﺗ ﻋﲆ ﻗﻴﺎس اﻟﻀﻮء اﻟـﺬ ي ﻳﻤـﺮ ﻋـﱪ أﺟﻮاء اﻟﻜﻮاﻛﺐ اﻟ ﻨﺠﻤﻴﺔ ﻔـ ﻗﺪ ﺗ ﴪ اﻧﺘﻔـﺎخ ﻋﴩـات اﻟﻜﻮاﻛـﺐ اﻟ ﻨﺠﻤﻴـﺔ ذات اﻟﻜﺜﺎﻓــﺔ ا ﺘﺪﻓﻘﺔ ﻣﻤﺎ ﻳﺴﺎﻋﺪ ﰲ ﺣﻞ ﻟﻐﺰ ﻃﻮ ﻳﻞ اﻷﻣﺪ ﰲ ﻋﻠﻢ اﻟﻜﻮاﻛﺐ اﻟ ﻨﺠﻤﻴﺔ . ﻳﺒﻠﻎ ﺣﺠﻢ اﻟﻜﻮﻛﺐ اﻟﻨﺠﻤﻲ " ﻧﺒﺘﻮن اﻟﺪاﻓﺊ " WASP-107b) ( أﻛﺜﺮ ﻣﻦ ﺛﻼﺛﺔ أرﺑﺎع ﺣﺠﻢ ﻛﻮﻛﺐ ا ﺸﱰي، وﻟﻜﻦ أﻗﻞ ﻣﻦ ﻋُﴩ ﻛﺘﻠﺘـﻪ وﻫﻮ ﻣﻦ أﻗﻞ اﻟﻜﻮاﻛﺐ ا ﻌﺮوﻓﺔ ﻛﺜﺎﻓﺔً . ﰲ ﺣ أن اﻟﻜﻮاﻛﺐ ا ﻨﺘﻔﺨـﺔ ﻟﻴﺴـﺖ ﻏـ إﻻ أ ﺷﺎﺋﻌﺔ ن ﻣﻌﻈﻤﻬﺎ أﻛﺜﺮ ﺳﺨﻮﻧﺔ وأﻛﺜـﺮ ﺿﺨﺎﻣﺔ وﺑﺎﻟﺘﺎﱄ ﻳﺴﻬﻞ ﺗﻔﺴ ﻫﺎ . أوﺿﺢ ﻟﻮﻳﺲ و ﻳﻠﺒﺎﻧﻜﺲ ﻣﻦ ﺟﺎﻣﻌﺔ وﻻﻳـﺔ أرﻳﺰوﻧﺎ و ا ﺆﻟﻒ اﻟﺮﺋ ﻟ ﻴﴘ ـ ﻠﻮرﻗـﺔ اﻟ ﺒﺤﺜﻴـﺔ ﻣﻨﺸـﻮرة ﰲ ﻣﺠﻠـﺔ ﻧﻴــﺘﴩ ": اﺳـﺘﻨﺎد إﱃ اً ﻧﺼﻒ ﻗﻄﺮه وﻛﺘﻠﺘﻪ وﻋﻤﺮه ودرﺟﺔ ﺣﺮارﺗﻪ اﻟﺪاﺧﻠﻴـﺔ ا ﻔﱰﺿـﺔ اﻋﺘﻘـﺪﻧﺎ أن اﻟﻜﻮﻛـﺐ اﻟﻨﺠﻤﻲ ) (WASP-107b ﻟﺪﻳﻪ ﻧﻮاة ﺻﺨﺮﻳﺔ اً ﺻﻐ ة ﺟﺪ ﻣﺤﺎﻃـﺔ ﺑﻜﺘﻠـﺔ ﺿـ ﺨﻤﺔ ﻣـﻦ اﻟﻬﻴﺪروﺟ واﻟﻬﻴﻠﻴﻮم ﻟﻜﻦ ﻛﺎن ﻣﻦ اﻟﺼﻌﺐ ﻓﻬﻢ ﻛﻴﻒ ﻳﻤﻜﻦ ﺜﻞ ﻫﺬ ه اﻟﻨﻮاة اﻟﺼﻐ أن ة ﺗ ﻜﺘﺴﺢ اﻟﻜﺜ ﻣﻦ اﻟﻐـﺎز ﺛـﻢ ﺗ ﺘﻮﻗـﻒ ﻋـﻦ اﻟﻨﻤﻮ ﺑﺎﻟﻜﺎﻣﻞ ﻟﻴﺼﺒﺢ ﻛﻮﻛﺒـﺎً ﺗﺒﻠـﻎ ﻛﺘﻠﺘـﻪ ﻛﺘﻠﺔ ﻛﻮﻛﺐ ا ﺸﱰي ." إذا ﻛﺎن اﻟﻜﻮﻛﺐ ) WASP-107 b ( ﻳﺤﺘـﻮي ﻋﲆ ﻛﺘﻠﺔ أﻛـﱪ ﻣـﻦ ﻛﺘﻠﺘـﻪ ﰲ ﻧﻮاﺗـﻪ ﻓﻤـﻦ ا ﻔﱰض أن ﻳﻜﻮن ﻪﻏﻼﻓ اﻟﺠﻮي ﻗﺪ اﻧﻜﻤﺶ ﺑﺎﻟﻔﻌﻞ ﻣﻊ اﻧﺨﻔﺎضﺣﺮا رة اﻟﻜﻮﻛﺐ ﺑﻤﺮور اﻟﻮﻗﺖ ﻣﻨﺬ ﺗﺸﻜﻠﻪ وﻣﻦ دون وﺟﻮد اً ﻣﺼﺪر ﻟﻠﺤﺮارة ﻹﻋﺎدة ﺗﻤﺪد اﻟﻐﺎز ﻳﻨﺒﻐﻲ أن ﻳﻜـﻮن اﻟﻜﻮﻛﺐ أﺻﻐﺮ ﺑﻜﺜ . ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أن ﻣﺴﺎﻓﺔ ا ﺪارﻳﺔ ﻟﻠﻜﻮﻛـﺐ WASP-107b ﺗﺒﻠﻎ 5 ﻣﻼﻳـ ﻣﻴـﻞ ﻓﻘـﻂ ــــ ) ﺳُﺒﻊ ا ﺴﺎﻓﺔ ﺑ ﻋﻄﺎرد واﻟﺸﻤﺲ ( ﻟﻜﻨﻪ ﻻ ﻳﺘﻠﻘﻰ ﻃﺎﻗﺔ ﻛﺎﻓﻴﺔ ﻣﻦ ﻧﺠﻤﻪ ﻟﻴﺘﻀﺨﻢ إﱃ . ﻫﺬا اﻟﺤﺪ ﻗﺎل دﻳﻔﻴـﺪ ﺳـﻴﻨﻎ ﻣـﻦ ﺟﺎﻣﻌـﺔ ﺟﻮﻧﺰ ﻫﻮﺑﻜﻨﺰ ا ﺆﻟـﻒ اﻟﺮﺋﻴـ ـ ﴘ ﻟﺪراﺳـﺔ ﻣﻮازﻳﺔ ﻧُـ ـ ﺎً ﴩت أﻳﻀـ ﰲ ﻣﺠﻠـﺔ ﻧﻴــﺘﴩ : ﻳﻌــﺪ " اﻟﻜﻮﻛــﺐ ) WASP-107b ( ﺎً ﻫــﺪﻓ ﺑﺎﻟﻨﺴﺒﺔ إﱃ ﺗﻠﺴﻜﻮب وﻳﺐ ﻷﻧﻪ أﻛﺜﺮ ﺑـﺮودة ﺑﺸﻜﻞ ﻛﺒ وأﻛﺜﺮ ﺷﺒﻬﺎً ﺑﻜﺘﻠﺔ ﻧﺒﺘـﻮن ﻣـﻦ اﻟﻌﺪﻳﺪ ﻣـ ﻦ اﻟﻜﻮاﻛـﺐ اﻷﺧـﺮى ﻣﻨﺨﻔﻀـﺔ اﻟﻜﺜﺎﻓﺔ ﻣﺜﻞ ﻛﻮاﻛﺐ ا ﺸﱰي اﻟﺴﺎﺧﻨﺔ اﻟﺘﻲ ﻛﻨﺎ ﻧﺪرﺳﻬﺎ . ﻧﺘﻴﺠﺔ ﻟﺬﻟﻚ ﻳﺠﺐ أن ﻧﻜـﻮن ﻗـﺎدرﻳﻦ ﻋـﲆ اﻛﺘﺸﺎف ا ﻴﺜﺎن واﻟﺠﺰﻳﺌﺎت اﻷﺧﺮى اﻟﺘﻲ ﻗﺪ ﺗﺰودﻧ ــﺎ ﺑﻤﻌﻠﻮﻣ ــﺎت ﺣ ــﻮل ﻛﻴﻤﻴﺎﺋ ــﻪ ودﻳﻨﺎﻣﻴﻜﻴﺎﺗ ـﻪ اﻟﺪاﺧﻠﻴ ـﺔ اﻟﺘ ـﻲ ﻻ ﻳﻤﻜﻨﻨ ـﺎ ا ﻟﺤﺼﻮل ﻋﻠﻴﻬﺎ ﻣﻦ ﻛﻮﻛـﺐ أﻛﺜـﺮ ﺳـﺨﻮﻧﺔ ﻟﺬﻟﻚو ﻳﺠﺐ أن ﻧﻜﻮن ﻗﺎدرﻳﻦ ﻋﲆ اﻛﺘﺸﺎف ا ﻴﺜﺎن واﻟﺠﺰﻳﺌﺎت اﻷﺧﺮى اﻟﺘـﻲ ﻳﻤﻜـﻦ أن ﺗﺰودﻧ ــﺎ ﺑﻤﻌﻠﻮﻣ ــﺎت ﺣ ــﻮل ﻛﻴﻤﻴﺎﺋ ــﻪ ودﻳﻨﺎﻣﻴﻜﻴﺎﺗ ـﻪ اﻟﺪاﺧﻠﻴ ـﺔ اﻟﺘ ـﻲ ﻻ ﻳﻤﻜﻨﻨ ـﺎ اﻟﺤﺼﻮل ﻋﻠﻴﻬﺎ ﻣﻦ ﻛﻮﻛﺐ أﻛﺜﺮ ﺳﺨﻮﻧﺔ ." إن ﻧﺼـﻒ ﻗﻄـﺮ اﻟﻜﻮﻛـﺐ WASP-107 b اﻟﻌﻤﻼق وﻏﻼﻓﻪ اﻟﺠﻮي وﻣـﺪاره ا ﺤﻴﻄـﻲ ﻳﺠﻌﻠﻪ ﻣﺜﺎﻟﻴ ﺎً ﻟﻠﺘﺤﻠﻴﻞ ا ﻟﻄﻴﻔﻲ ﻋﻨﺪ ﻋﺒـﻮره أﻣﺎم ﻧﺠﻤﻪ وﻫﻲ ﻃﺮﻳﻘﺔ ﺗﺴﺘﺨﺪم ﻟﺘﺤﺪﻳـﺪ اﻟﻐﺎزات ا ﺨﺘﻠﻔﺔ ﰲ اﻟﻐﻼف اﻟﺠﻮي ﻟﻜﻮﻛـﺐ ﻧﺠﻤﻲ ﺑﻨﺎءً ﻋ ﲆ ﻛﻴﻔﻴﺔ ﺗﺄﺛ ﻫﺎ ﻋـﲆ ﺿـﻮء اﻟﻨﺠ ﻢ وﺑﺪﻣﺞ اﻷرﺻﺎد ا ﺄﺧﻮذة ﻣﻦ ﻛـﺎﻣ ا ﻧ ﻛـﺎم ) ﻛـﺎﻣ ا ﻟ ﻸﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤـﺮاء اﻟﻘﺮﻳﺒﺔ ( وﻛﺎﻣ ا أداة ا ) ﻣ ي ﻷﺷﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء ا ﺘﻮﺳﻄﺔ ( ﻟﺘﻠﺴﻜﻮب وﻳﺐ وﻛﺎﻣ ا ﻫﺎﺑﻞ WFC3 واﺳﻌﺔ ا ﺠﺎل ﺗﻤﻜـﻦ ﻓﺮﻳـﻖ وﻳﻠﺒﺎﻧﻜﺲ ﻣﻦ ﺑﻨﺎء ﻃﻴﻒ واﺳﻊ اﻟﻨﻄﺎق ﻣﻦ 0.8 إﱃ 12.2 ﻣﻴﻜﺮون ﻣﻦ اﻟﻀﻮ ء ا ﻤـﺘﺺ ﺑﻮاﺳﻄﺔ اﻟﻐﻼف اﻟﺠﻮي ﻟ ﻠﻜﻮﻛـﺐ اﻟﻨﺠﻤـﻲ WASP-107b) ( وﺑﺎﺳـــﺘﺨﺪام ﻣﻄﻴـــﺎف اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء اﻟﻘﺮﻳﺒـﺔ ﻟﺘﻠﺴـﻜﻮب وﻳﺐ ﺑﻨﻰ ﻓﺮﻳﻖ ﺳﻴﻨﻎ ﺎ ﻃﻴﻔ ﻛﺬﻟﻚ ﻣﺴـﺘﻘﻼً ﻳﻐﻄﻲ ا ﺪى ﻣﻦ 2.7 إﱃ 5.2 . ﻣﻴﻜﺮون إن دﻗﺔ اﻟﺒﻴﺎﻧﺎت ﺗﺠﻌﻞ ﻣﻦ ا ﻤﻜﻦ اﻛﺘﺸﺎف وﻓﺮة ﺛﺮوة ﻣﻦ اﻟﺠﺰﻳﺌﺎت ﺎ ﻗﻴﺎﺳـﻬ و ﺑﻤـﺎ ﰲ ذﻟـﻚ ﺑﺨـﺎر ا ـﺎء وا ﻴﺜـﺎن وﺛـﺎﻧﻲ أﻛﺴـﻴﺪ اﻟﻜﺮﺑﻮن وأول أﻛﺴﻴﺪ اﻟﻜﺮﺑﻮن وﺛﺎﻧﻲ أﻛﺴﻴﺪ اﻟﻜﱪﻳﺖ واﻷﻣﻮﻧﻴﺎ .