Free Astronomy Magazine September-October 2023 ARABIC VERSION

17 ocated in the constellation Sagit- tarius, the young star HD 169142 is host to a giant protoplanet em- bedded within its dusty, gas-rich protoplanetary disk. This artist’s conception shows the Jupiter-like planet interacting with and heating nearby molecular gas, driving out- flows seen in several emission lines, including those from shock-tracing molecules like SO and SiS, and the commonly seen 12 CO and 13 CO. (Not to scale) [(ESO/NAOJ/NRAO), M. Weiss (NRAO/AUI/NSF)] earlier this year, scien- tists at the University of Liège and Monash Uni- versity confirmed that one such candidate — HD 169142 b— is, in fact, a giant Jupiter-like protoplanet. The dis- coveries revealed in a new analysis of archival data from ALMA may now make it easier for scientists to detect, confirm, and ultimately characterize, proto- planets forming around young stars. “When we looked at HD 169142 and its disk at submillimeter wave- lengths, we identified several compelling chemical signatures of this recently-confirmed gas giant protoplanet,” said Charles Law, an as- tronomer at the Center for Astrophysics | Har- vard & Smithsonian, and the lead author of the new study. “We now have confirmation that we can use chemi- cal signatures to figure out what kinds of planets there might be forming in the disks around young stars.” The team focused on the HD 169142 system because they believed that the presence of the HD 169142 b giant protoplanet was likely to be accompanied by detectable chemical signatures, and they thought to be associated with pro- toplanets in other disks. But for the first time, the team also detected sil- icon monosulfide (SiS). This came as a surprise because in order for SiS emission to be detectable by ALMA, silicates must be released from nearby dust grains in massive shock waves caused by gas traveling at high velocities, a behavior typically resulting from outflows that are driven by giant protoplanets. “SiS was a molecule that we had never seen before in a protoplane- tary disk, let alone in the vicinity of a giant protoplanet,” Law said. “The detection of SiS emission popped out at us because it means that this protoplanet must be producing powerful shock waves in the sur- rounding gas.” With this new chemical approach for detecting young protoplanets, scien- tists may be opening a new window on the Universe and deepening their understanding of exoplanets. Protoplanets, especially those that are still embedded in their parental circumstellar disks such as in the HD 169142 system, provide a direct con- nection with the known exoplanet population. “There’s a huge diver- sity in exoplanets and by using chemical signatures observed with ALMA, this gives us a new way to understand how different proto- planets develop over time and ulti- mately connect their properties to that of exoplanetary systems,” said Law. “In addition to providing a new tool for planet-hunting with ALMA, this discovery opens up a lot of exciting chemistry that we’ve never seen before. As we continue to survey more disks around young stars, we will inevitably find other interesting but unanticipated mole- the presence of its large, dust- and gas-rich circumstellar disk that is viewed nearly face-on. Several pro- toplanet candidates have been iden- tified over the last decade, and were right. Law’s team detected carbon monoxide (both 12 CO and its isotopologue 13 CO) and sulfur monoxide (SO), which had previ- ously been detected and were cules, just like SiS. Discoveries such as this imply that we are only just scratching the surface of the true chemical diversity associated with protoplanetary settings.”     L ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 17 واﻟﺬي ﻳﻤﻜﻦ رؤﻳﺘﻪ ﺗﻘﺮﻳ ﺎً ﺒ وﺟﻬًﺎ ﻟﻮﺟﻪ . ﺗـﻢ اﻟﺘﻌﺮف ﻋﲆ اﻟﻌﺪﻳﺪ ﻣـﻦ اﻟﻜﻮاﻛـﺐ اﻷوﻟ ﻴـﺔ ا ﺮﺷﺤﺔ ﻋﲆ ﻣﺪى اﻟﻌﻘﺪ ا ـﺎﴈوﰲ وﻗـﺖ ﺳﺎﺑﻖ ﻣﻦ ﻫﺬا اﻟﻌﺎم أﻛﺪ اﻟﻌﻠﻤﺎء ﰲ ﺟﺎﻣﻌـﺔ ﻟﻴﻴﺞ وﺟﺎﻣﻌﺔ ﻣﻮﻧﺎش أن أﺣﺪ ﻫﺬه اﻟﻜﻮاﻛﺐ ا ﺮﺷﺤﺔ - HD 169142 b - ﻫﻮ ﰲ اﻟﻮاﻗـﻊ ﻟﻴﻴﺞ وﺟﺎﻣﻌﺔ ﻣﻮﻧﺎش أن أﺣﺪ ﻫﺬه اﻟﻜﻮاﻛﺐ ا ﺮﺷﺤﺔ اﻟـﺬي ﻳﺴﻤﻰ HD 169142 b ﻫـﻮ ﰲ اﻟﻮاﻗﻊ ﻛﻮﻛﺐ أوﱄ ﻋﻤـﻼق ﻳﺸـــــﺒﻪ ا ﺸـــــﱰي إن . اﻻﻛﺘﺸﺎﻓﺎت اﻟﺘﻲ ﺗﻢ اﻟﻜﺸـﻒ ﻋﻨﻬﺎ ﰲ ﺗﺤﻠﻴﻞ ﺟﺪﻳﺪ ﻟﻠﺒﻴﺎﻧﺎت اﻷرﺷﻴﻔﻴﺔ ﻣﻦ ﻣﺮﺻﺪ أ ﺎ ﻗـﺪ ﺗﺴــﻬﻞ اﻵن ﻋــﲆ اﻟﻌﻠﻤــﺎء اﻛﺘﺸـﺎف وﺗﺄﻛﻴـﺪ وﺗﻮﺻـﻴﻒ اﻟﻜﻮاﻛﺐ اﻷوﻟﻴﺔ اﻟﺘﻲ ﺗﺘﺸـﻜﻞ ﺣﻮل اﻟﻨﺠـﻮم اﻟﻴﺎﻓﻌـﺔ . ﻗـﺎل ﺗﺸـﺎرﻟﺰ ﻟـﻮ ﻋـﺎﻟﻢ اﻟﻔﻠـﻚ ﰲ ﻣﺮﻛــﺰ اﻟﻔﻴﺰﻳــﺎء اﻟﻔﻠﻜﻴــﺔ ﻫﺎرﻓــﺎرد وﺳﻤﻴﺜﺴــﻮﻧﻴﺎن، وا ﺆﻟﻒ اﻟﺮﺋﻴـ ـ ﴘ ﻟﻠﺪراﺳـﺔ اﻟﺠﺪﻳﺪة :" ﻋﻨﺪﻣﺎ ﻧﻈﺮﻧﺎ ﺑﻌﻤﻖ إﱃ اﻟــــﻨﺠﻢ HD 169142 وﻗﺮﺻﻪ ﻋﻨﺪ اﻷﻃﻮال ا ﻮﺟﻴـﺔ دون ا ﻠﻴﻤﱰﻳﺔ ﺣﺪدﻧﺎ اﻟﻌﺪﻳـﺪ ﻣـﻦ اﻟﺘﻮﻗﻴﻌـﺎت اﻟﻜﻴﻤﻴﺎﺋﻴ ـﺔ ا ﻘﻨﻌـﺔ ﻟﻬـﺬا اﻟﻜﻮﻛـﺐ اﻷوﱄ اﻟﻐـﺎزي اﻟﻌﻤـﻼق اﻟـﺬي ﺗـﻢ ﺗﺄﻛﻴﺪه ﻣـﺆﺧﺮاً و اﻵن ﻳﻤﻜﻨﻨـﺎ اﺳ ــــﺘﺨﺪام اﻟﺒﺼــــﻤﺎت اﻟﻜﻴﻤﻴﺎﺋﻴــﺔ ﻌﺮﻓــﺔ أﻧــﻮاع اﻟﻜﻮاﻛﺐ اﻟﺘﻲ ﻗـﺪ ﺗﺘﺸـ ﰲ ﻜﻞ اﻷﻗــﺮاصﺣــﻮل اﻟﻨﺠــﻮم اﻟﺸﺎﺑﺔ ". رﻛـﺰ اﻟﻔﺮﻳـﻖ ﻋـﲆ ﻧﻈ ـﺎم HD 169142 ﻷﻧﻬ ـﻢ اﻋﺘﻘـﺪوا أن وﺟـﻮد اﻟﻜﻮﻛـﺐ اﻷوﱄ اﻟﻌﻤﻼق HD 169142 b ﻳﻜـﻮن ﻣﺼـﺤﻮﺑ ﺎً ﺑﺒﺼـﻤﺎت ﻛﻴﻤﻴﺎﺋﻴـﺔ ﻳﻤﻜـ ﻦ اﻛﺘﺸـﺎﻓﻬﺎ وﻛـﺎﻧﻮا ﻋـﲆ ﺣـﻖ . اﻛﺘﺸـﻒ اﻟﻜﱪﻳﺖ (SO) واﻟـﺬي ﺗـﻢ اﻛﺘﺸـﺎﻓﻪ ﺳـﺎﺑﻘ ﺎً وﻳُﻌﺘﻘـﺪ أﻧـﻪ ﻣـﺮﺗﺒﻂ ﺑﺎﻟﻜﻮاﻛـﺐ اﻷوﻟﻴــﺔ ﰲ أﻗﺮاص أﺧﺮى وﻟﻜﻦ ﻷول ﻣﺮة اﻛﺘﺸﻒ اﻟﻔﺮﻳﻖ أﻳﻀًﺎ أﺣﺎدي ﻛﱪﻳﺘﻴﺪ اﻟﺴﻴﻠﻴﻜﻮن ) (SiS و ﻛﺎن ﻫﺬا ﺑﻤﺜﺎﺑﺔ ﻣﻔﺎﺟﺄة ﻷﻧﻪ ﻟﻜﻲ ﻳﺘﻤﻜﻦ ﻣﺮﺻﺪ أ ﺎ ﻣـﻦ اﻛﺘﺸـﺎف اﻧﺒﻌـﺎث أﺣـﺎدي ﻛﱪﻳﺘﻴﺪ اﻟﺴﻴﻠﻴﻜﻮن ﻳﺠﺐ إﻃﻼق اﻟﺴﻴﻠﻴﻜﺎت ﻣـﻦ ﺣﺒﻴﺒـﺎت اﻟﻐﺒـﺎر اﻟﻘﺮﻳﺒـﺔ ﰲ ﻣﻮﺟـﺎت ﺻﺪﻣﻴﺔ ﺿﺨﻤﺔ ﻧﺎﺟﻤﺔ ﻋـﻦ اﻧﺘﻘـﺎل اﻟﻐـﺎز ـﺑ ﴪﻋﺎت ﻋﺎﻟﻴﺔ وﻫﻮ ﺳﻠﻮك ﻳﻨﺘﺞ ﻋﺎدةً ﻋﻦ اﻟﺘﺪﻓﻘﺎت اﻟﺨﺎرﺟﺔ اﻟﺘﻲ ﺗﺤﺮﻛﻬﺎ اﻟﻜﻮاﻛـﺐ اﻷوﻟﻴﺔ اﻟﻌﻤﻼﻗﺔ ، وﻗﺎل ﻟـﻮ ﻛـ : " ﺎن أﺣـﺎدي ﻛﱪﻳﺘﻴﺪ اﻟﺴﻴﻠﻴﻜﻮن ﺟﺰﻳﺌ ﺎً ﻟﻢ ﻧﺮه ﻣﻦ ﻗﺒﻞ ﰲ ﻗـﺮص ﻛـﻮﻛﺒﻲ أوﱄ ﻧﺎﻫﻴـﻚ ﻋـﻦ و ﺟـﻮده ﺑﺎﻟﻘﺮب ﻣﻦ ﻛﻮﻛﺐ أوﱄ ﻋﻤﻼق ، ﻟﻘﺪ ﻇﻬﺮ ﻟﻨﺎ اﻛﺘﺸﺎف اﻧﺒﻌﺎث أﺣﺎدي ﻛﱪﻳﺘﻴﺪ اﻟﺴﻴﻠﻴﻜﻮن ﻷﻧ ﻪ ﻳﻌﻨﻲ أن ﻫﺬا اﻟﻜﻮﻛﺐ اﻷوﱄ ﻻ ﺑﺪ أن ﻳﻨﺘﺞ ﻣﻮﺟﺎ ت ﺻﺪﻣﻴﺔ ﻗﻮﻳﺔ ﰲ اﻟﻐﺎز ا ﺤﻴﻂ ﺑﻪ " . وﻣﻊ ﻫﺬا اﻟﻨﻬﺞ اﻟﻜﻴﻤﻴﺎﺋﻲ اﻟﺠﺪﻳﺪ ﻻﻛﺘﺸﺎف ا ﻟﻜﻮاﻛﺐ اﻷوﻟﻴﺔ اﻟﺸﺎﺑﺔ رﺑﻤﺎ ﻳﻔﺘ ﺢ اﻟﻌﻠﻤـﺎء ﻧﺎﻓﺬة ﺟﺪﻳﺪة ﻋﲆ اﻟﻜﻮن وﻳﻌﻤﻘﻮن ﻓﻬﻤﻬﻢ ﻟﻠﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴﺔ . ﺗﻮﻓﺮ اﻟﻜﻮاﻛـﺐ اﻷوﻟﻴـﺔ وﺧﺎﺻـﺔ ﺗﻠـﻚ اﻟﺘـﻲ ﻻ ﺗـﺰال ﰲ اﻷﻗـﺮاص ا ﺤﻴﻄﺔ ﺑﺎﻟﻨﺠﻮم ﻛﻤﺎ ﻫﻮ اﻟﺤـﺎل ﰲ ﻧﻈـﺎم HD 169142 اﺗﺼـــﺎﻻً ﻣﺒـــﺎﴍ اً ﻣـــﻊ ﻣﺠﻤﻮﻋﺎت اﻟﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴﺔ ا ﻌﺮوﻓﺔ . ﻗﺎل ﻟـﻮ " : ﻫﻨـﺎ ك ﺗﻨـﻮع ﻛﺒـ ﰲ اﻟﻜﻮاﻛـﺐ اﻟﺨﺎرﺟﻴﺔ وﺑﺎﺳﺘﺨﺪام اﻟﺒﺼﻤﺎت اﻟﻜﻴﻤﻴﺎﺋﻴﺔ اﻟﺘﻲ ﺗﻢ رﺻﺪﻫﺎ ﺑﻮاﺳﻄﺔ ﻣﺮﺻﺪ أ ﺎ ﻓﺈن ﻫﺬا ﻳﻤﻨﺤﻨﺎ ﻃﺮﻳﻘﺔ ﺟﺪﻳﺪة ﻟﻔﻬﻢ ﻛﻴﻔﻴﺔ ﺗﻄـﻮر اﻟﻜﻮاﻛﺐ اﻷوﻟﻴـﺔ ا ﺨﺘﻠﻔـﺔ ﺑﻤـﺮور اﻟﻮﻗـﺖ ورﺑﻂ ﺧﺼﺎﺋﺼـﻬﺎ ﰲ اﻟﻨﻬﺎﻳـﺔ ﺑﺨﺼـﺎﺋﺺ أﻧﻈﻤﺔ اﻟﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴﺔ ﺑﺎﻹﺿﺎﻓﺔ إﱃ ﺗﻮﻓ أداة ﺟﺪﻳ ـﺪة ﻟﺼــﻴﺪ اﻟﻜﻮاﻛ ـﺐ ﺑﺎﺳـﺘﺨﺪام ﻣﺮﺻﺪ أ ﺎ ﻓﺈن ﻫﺬا اﻻﻛﺘﺸﺎف ﻳﻔﺘﺢ اﻟﺒـﺎب أﻣﺎم اﻟﻜﺜ ﻣﻦ اﻟﻜﻴﻤﻴـﺎ ء ا ﺜـ ة اﻟﺘـﻲ ﻟـﻢ ﻧﺸﻬﺪﻫﺎ ﻣﻦ ﻗﺒﻞ وﻣﻊ اﺳﺘﻤﺮارﻧﺎ ﰲ ﻣﺴـﺢ ا ﺰﻳﺪ ﻣﻦ اﻷﻗﺮاصﺣـﻮل اﻟﻨﺠـﻮم اﻟﻴﺎﻓﻌـﺔ ﺳﻨﺠﺪ ﺣﺘﻤﺎً ﺟﺰﻳﺌﺎت أﺧﺮى ﻣﺜ ة ﻟﻼﻫﺘﻤﺎم ﻏ ﻣﺘﻮﻗﻌـﺔ . إن ﻣﺜـﻞ ﻫـﺬه اﻻﻛﺘﺸـﺎﻓﺎت ﺗﺸ إﱃ أﻧﻨﺎ ﻻ ﻧﺰال ﰲ ﺑﺪاﻳﺔ اﻟﺘﻌـﺮف ﻋـﲆ اﻟﺘﻨــﻮع اﻟﻜﻴﻤﻴــﺎﺋﻲ اﻟﺤﻘﻴﻘــﻲ ا ــﺮﺗﺒﻂ ﺑﺈﻋﺪادات اﻟﻜﻮاﻛﺐ اﻷوﻟﻴﺔ . - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 3