Free Astronomy Magazine September-October 2025 ARABIC VERSION

SEPTEMBER-OCTOBER2025 very massive collections of galaxies, known as galaxy clusters, that are themselves bound by gravity. These galaxy clusters act as gravita- tionallenses,magnifyingthelight of background galaxies. “Gravita- tional lensing allows us to infer the distribution of dark matter,” said JamesJee,aco-author,professorat YonseiUniversity,andresearchasso- ciate at UC Davis in California. To visualize gravitational lensing and dark matter, think of a pond filledwithclearwaterandpebbles. “You cannot see the water unless thereiswind,whichcausesripples,” Jee explained. “Those ripples dis- tort the shapes of the pebbles below, causing the water to act like alens.” Thesamethinghappensin space,butthewaterisdarkmatter and the pebbles are background galaxies.Inall,theteammeasured thousandsofgalaxiesinWebb’sim- ages to accurately “weigh” both the visible and invisible mass in these galaxy clusters. They also carefully mapped and measuredthecollectivelightemit- ted by stars that are no longer bound to individual galaxies — known as intracluster stars. TherevisedmapoftheBulletClus- ter is shown in a new image: Lay- ered on top of an image from Webb’s NIRCam (Near-Infrared Camera) is data from NASA’s Chan- dra X-ray Observatory that shows hotgasinpink,includingthebullet shape at right. Refined measure- ments of the dark matter, calcu- latedbytheteamusingWebb’sob- servations,arerepresentedinblue. Theirfindingsarepersuasive: “We اﻟــــﺘﻘﻂ ــــﺐ اﻟﻔﻀــــﺎﺋﻲ اﻟﺘــــﺎﺑﻊ ﻟﻮ ﺎﻟــــﺔ ﻧﺎﺳــــﺎ اﻟﻤﻨﻄﻘــــﺔ اﻟﻤﺮﻛﺰ ــــﺔ ﻟﻌﻨﻘــــﻮد اﻟﺮﺻﺎﺻـــــﺔ ﺗﻠﺴــــ ﻮبﺟــــ ﻤﺲو ﺎﺳﺘﺨﺪام ﺎﻣ ا اﻷﺷﻌﺔ ﺗﺤﺖ اﻟ ـ ﻤﺮاء اﻟﻘﺮ ﺔ ﻧ ﺎم ) .( ﺿـ ﻤ ﻳﺤﺘﻮي اﻟﻤﺸـﻬﺪ ﻋﻠـﻰﻋﻨﻘـﻮدﻳﻦ ﻣﺠـﺮ اﻟﻤﺠــﺮة اﻟــ ﻋﻠـﻰﺟــﺎﻧ ـ ﺤﻠﺰوﻧ ﺔ اﻟﻜﺒــ ة ذات اﻟﻠــﻮن اﻷزرق اﻟﻔــﺎﺗﺢ ﻓــﻲ اﻟﻤﺮﻛــﺰ . ﻛﺸــﻔﺖﺻــﻮر ﺗﻠﺴــ ﻮب ــﺐ و اﻟﺪﻗ ﻘﺔ ﻋﻦ ﻣﺤﺎورﻣ ﺠﺮ ﺔ أ ﻌﺪ وأﺟﺮام ﺧﺎﻓﺘﺔ ﻣﻤﺎ ﺳﻤﺢ اﻟﻤﺠﺮات ﺘﺤﻠﻴﻞ ﻤ ﺔ اﻟﻜﺘﻠﺔ ﻓﻲﻋﻨﻘﻮد . ﻣﺮﺗﺒﻄﺘـﺎن ﺑﺒﻌﻀـﻬﻤﺎ ﺑﻮاﺳـﻄﺔ اﻟﺠﺎذﺑﻴـﺔ . ﺗﻌﻤﻞ ﻫﺬه ا ﻟﻌﻨﺎﻗﻴﺪ ا ﺠﺮﻳﺔ ﻛﻌﺪﺳﺎت ﺟﺎذﺑﻴﺔ ﺗُﻜﱪ ﺿﻮ ء ا ﺠﺮات اﻟﺨﻠﻔﻴﺔ . ﻳﻘﻮل ﺟﻴﻤﺲ ﺟﻲ ا ﺆﻟﻒ ا ﺸﺎرك واﻷﺳﺘﺎذ ﰲ ﺟﺎﻣﻌﺔ ﻳﻮﻧﴘ واﻟﺒﺎﺣﺚ ا ﺸـﺎرك ﰲ ﺟﺎﻣﻌـﺔ ﻛﺎﻟﻴﻔﻮرﻧﻴﺎ دﻳﻔﻴﺲ ﻛﺎﻟﻴﻔﻮ ﰲ : " رﻧﻴﺎ ﺗﺘﻴﺢ ﻟﻨـﺎ ﻋﺪﺳـﺔ اﻟﺠﺎذﺑﻴ ـﺔ اﺳـﺘﻨﺘﺎج ﺗﻮزﻳ ـﻊ ا ـﺎدة ا ﻈﻠﻤﺔ ." ﻟﺘﺼﻮر ﻋﺪﺳـﺔ اﻟﺠﺎذﺑﻴـﺔ وا ـﺎدة ا ﻈﻠﻤﺔ، ﺗﺨﻴـﻞ ﺑﺮﻛـﺔ ﻣﻠﻴﺌـﺔ ﺑﻤـﺎء ﺻـﺎفٍ و وﺣﴡ ﻻ ﻳﻤﻜﻦ رؤﻳﺔ ا ﺎء إﻻ ﺑﻮﺟﻮد رﻳـﺎح ﺗﺴﺒﺐ ﺗﻤﻮﺟـﺎت وﻫـﺬه اﻟﺘﻤﻮﺟـﺎت ﺗﺸـﻮه أﺷﻜﺎل اﻟﺤ ـ ﴡ أﺳﻔﻠﻪ ﻣﻤﺎ ﻳﺠﻌﻞ ا ﺎء ﻳﻌﻤﻞ ﻳ". ﺳﺎت ﻌﺪ اﻟ ﻋﻤﻞ ـ ﺤـﺪث اﻟـ ﴚء ﻧﻔﺴـﻪ ﰲ اﻟﻔﻀﺎء ﻟﻜﻦ ا ﺎء ﻣـﺎدة ﻣﻈ ﻠﻤـﺔ واﻟـ ﺤﴡ ـ اﻟ ﻣﺠﺮات . ﺨﻠﻔﻴﺔ إﺟﻤﺎﻻً ﻗﺎم اﻟﻔﺮﻳﻖ ﺑﻘﻴـﺎس آﻻف ا ﺠـﺮات ﰲ ﺗﻠﺴﻜﻮب ﺻﻮر وﻳﺐ ﻟﻮزن اﻟﻜﺘﻠﺔ ا ﺮﺋﻴﺔ وﻏ ا ﺮﺋﻴﺔ ﰲ ﻫﺬه اﻟﻌﻨﺎﻗﻴﺪ ا ﺠﺮﻳـﺔ ﺑﺪﻗـﺔ . ﻛﻤـﺎ ﻗﺎﻣﻮا ﺑﺮﺳﻢ ﺧﺮﻳﻄﺔ وﻗﻴﺎس اﻟﻀﻮء اﻟﺠﻤﺎﻋﻲ ا ﻨﺒﻌﺚ ﻣﻦ اﻟﻨﺠﻮم ا ﻟﺘـﻲ ﻟـﻢ ﺗﻌـﺪ ﻣﺮﺗﺒﻄـﺔ ﺑﻤﺠﺮات ﻓﺮدﻳـﺔ وا ﻌﺮوﻓـﺔ ﺑﺎﺳـﻢ اﻟﻨﺠـﻮم داﺧﻞ اﻟﻌﻨﻘـﻮد . ﺗﻈﻬـﺮ اﻟﺨﺮﻳﻄـﺔ ا ُﻨﻘﺤـﺔ ﻟﻌﻨﻘﻮد اﻟﻄﻠﻘﺔ ﰲ ﺻﻮرة ﺟﺪﻳﺪة : ﻓﻮق ﺻﻮرة ﻣﻦ ﻛﺎﻣ ا وﻳﺐ اﻟﻘﺮﻳﺒﺔ ﻣـﻦ اﻷﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء ﻧ ﻛﺎم ) ( ﺗﻮﺟﺪ ﺑﻴﺎﻧﺎت ﻣـﻦ ﻣﺮﺻـﺪ ﺗﺸﺎﻧ ﺪرا ﻟﻸﺷﻌﺔ اﻟﺴﻴﻨﻴﺔ اﻟﺘﺎﺑﻊ ﻟ ﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ ﺗُ ﻈﻬﺮ ﻏﺎزاً ﺳﺎﺧﻨﺎً ﺑﺎﻟﻠﻮن اﻟﻮردي ﺑﻤﺎ ﰲ ذﻟﻚ ﺷـﻜﻞ اﻟﺮﺻﺎﺻـﺔ ﻋـﲆ اﻟﻴﻤـ . اﻟﻘﻴﺎﺳـﺎت ا ُﺤﺴّﻨﺔ ﻟﻠﻤﺎدة ا ﻈﻠﻤﺔ، اﻟﺘﻲ ﺣﺴﺒﻬﺎ اﻟﻔﺮﻳﻖ ﺷﻜﻞ اﻟﻄﻠﻘﺔ ﻋﲆ اﻟﻴﻤ اﻟ. ﻘﻴﺎﺳﺎت ا ﺤﺴﻨﺔ ﻟﻠﻤــﺎدة ا ﻈﻠﻤــﺔ اﻟﺘــﻲ ﺣﺴــﺒﻬﺎ اﻟﻔﺮﻳــﻖ ﺑﺎﺳـﺘﺨﺪام أرﺻـﺎد ﺗﻠﺴـﻜﻮب وﻳـﺐ ﻣﻤﺜﻠـﺔ ﺑﺎﻟﻠﻮن اﻷزرق . ﻗﺎل ﺗﺸـﺎ " : أﻛـﺪﻧﺎ أن اﻟﻀـﻮء داﺧﻞ اﻟﻌﻨﻘﻮد ﻳﻤﻜﻦ أن ﻳﺤﻤﻞ آﺛﺎر اً ﻣﻮﺛﻮﻗـﺔ ﻟﻠﻤــﺎدة ا ﻈﻠﻤــﺔ ﺣﺘــﻰ ﰲ ﺑﻴﺌــﺔ ﺷــﺪﻳﺪة اﻟﺪﻳ ﻨﺎﻣﻴﻜﻴﺔ ﻣﺜﻞ ﻋﻨﻘﻮد اﻟ . ﻄﻠﻘﺔ ﻟﺬﻟﻚ اﻟﻨﺘﺎﺋﺞ ﻣﻘﻨﻌﺔ و ﻫﺬا اﻻﻛﺘﺸـﺎف ﻳﻔـﺘﺢ آﻓﺎ ﻗًﺎ ﺟﺪﻳﺪة ﻟﻔﻬﻤﻨﺎ ﻟﻠﻤﺎدة ا ﻈﻠﻤـﺔ وﻳـﻮﻓﺮ أداة ﻗﻮﻳﺔ ﺰﻳﺪ ﻣﻦ اﻟﺒﺤﺚ ﰲ ﻋﻠﻢ اﻟﻜﻮﻧﻴﺎت . ـــــ ﺳﺒﺘﻤﺒﺮ - ﺃﻛﺘﻮﺑﺮ 2 0 2 5 [NASA, ESA, CSA, STScI, CXC − James Jee (Yonsei University, UC Davis), Sangju Cha (Yonsei University), Kyle Finner (Caltech/IPAC)]