Free Astronomy Magazine January-February 2024 ARABIC VERSION

[ mal galaxies that are located farther away beyond the Virgo Cluster. To distinguish the candidate UCD progenitors from the background galaxies, the team performed fol- low-up spectroscopic studies with Gemini North to obtain more con- crete measurements of their dis- tances. These observations allowed the astronomers to eliminate all of the background galaxies from their samples until only the UCDs within the Virgo Cluster remained. Scattered among this vast survey are many dwarf galaxies that contain ultra-compact central star clusters. These galaxies represent the early stages of the transformation process and suggest that after neighboring massive galaxies strip these dwarfs of their outer layers of stars and gas, what remains will be an object identical to the late-stage UCDs that have already been identified. The researchers also found many objects with very extended and dif- fuse stellar envelopes around them, indicating that they are currently in the throes of transitioning as their stars and dark matter is stripped away. Within their extensive sample the team identified objects at sev- eral other stages of the evolution- ary process that, when placed in sequence, tell a compelling story of the morphology of UCDs. ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 32 اﻟﻤﺠـﺮة NGC 3628 ــﺔ أﺣ اﻟﻤﻠﻘ ﺎﻧًـﺎ ﻤﺠــﺮة ﻫﻤ ﻏــﺮأو ﻣﺠــﺮة ﺳــﺎرة، ﻫــﻲﻣﺠــﺮة ــﺔ ﺣﻠﺰوﻧ ﻏــــــ ﻣﺤــــــﺪدة ﺗ ﻌــــــﺪ ﺣــــــﻮاﻟﻲ 35 ﻣﻠﻴــــــﻮنﺳـــــــﻨﺔ ــــﺔ اﻷﺳــــﺪ ﺿــــﻮﺋ ﺔ ﻋــــﻦ ﻮﻛ . و ﻤﺘــــﺪ إﻟــــﻰ ﺴــــﺎر اﻟﻤﺠـــﺮة NGC 3628 ﻟﻨﺤـــﻮ 300 أﻟـــﻒﺳـــﻨﺔ ﺿـــــــﻮﺋ ﺔ، وﻫـــــــﻮ " ـــــــﺰر ذﻳـــــــﻞ اﻟﻤـــــــﺪ وا "- وﻫـــــــﻮ ﻣﻨﻄﻘـــــﺔ ﻣﺴـــــﺘﻄ ﻠﺔ ﻣـــــﻦ اﻟﻨﺠـــــﻮم ﺗﻨﺸـــــﺄ ﻧﺘﻴﺠـــــﺔ ﻟﺘﻔﺎﻋﻞ اﻟـ ـ ﺠﺎذﺑ ﺔ ﻣـﻊ ﻣﺠـﺮة ﺮىأﺧـ وداﺧـﻞ ذﻳـﻞ اﻟﻤــــﺪ واﻟــــ ـ ﺠﺰرﻫــــﺬا ﺗﻮﺟــــﺪ ﻣﺠــــﺮة ﻗﺰﻣــــﺔ ﻓﺎﺋﻘــــﺔ اﻟﺼﻐﺮﺗﻌﺮف ﺎﺳﻢ NGC 3628-UCD1 ﻟﺘﻤﻴﻴﺰ أﺳﻼف ا ﺠﺮ ات اﻟﻘﺰﻣﺔ ﻓﺎﺋﻘﺔ اﻟﺼﻐﺮ ا ﺮﺷﺤﺔ ﻋﻦ ا ﺠﺮات اﻟﺨﻠﻔﻴﺔ أﺟﺮى اﻟﻔﺮﻳﻖ دراﺳﺎت ﻃﻴﻔﻴﺔ ﻣﺘ ﺎﺑﻌﺔ ﺘ ﺑﻮاﺳﻄﺔ ﺗﻠﺴـﻜﻮب ﺟﻴﻤﻨﻲ ﻧﻮرث ﻟﻠﺤﺼﻮل ﻋﲆ ﻗﻴﺎﺳـﺎت أﻛﺜـﺮ ﺗﺤﺪﻳﺪًا ﻟﻠﻤﺴﺎﻓﺎت اﻟﺨﺎﺻﺔ ﺑﻬ .ﺎ ﺳﻤﺤﺖ ﻫﺬه اﻻرﺻﺎد ﻟﻌﻠﻤﺎء اﻟﻔﻠـﻚ ﺑﺈزاﻟـﺔ ﺟﻤﻴﻊ ا ﺠﺮات اﻟﺨﻠﻔﻴﺔ ﻣـﻦ ﻋﻴﻨﺎﺗﻬـ ﺎ ﺣﺘـﻰ ﺑﻘﻴﺖ ﻓﻘﻂ ا ﺠﺮات اﻟﻘﺰﻣﺔ ﻓﺎﺋﻘـﺔ اﻟﺼـﻐﺮ داﺧﻞ ﻋﻨﻘﻮد اﻟﻌﺬراء . ﺗﻨﺘﴩ ﺑ ﻫﺬا ا ﺴﺢ اﻟﻮاﺳـﻊ اﻟﻌﺪﻳـﺪ ﻣـﻦ ا ﺠﺮات اﻟﻘﺰﻣﺔ اﻟﺘﻲ ﺗﺤﺘﻮي ﻋﲆ ﻣﺠﻤﻮﻋﺎت ﻧﺠﻤﻴﺔ ﻣﺮﻛﺰﻳﺔ ﻓﺎﺋﻘﺔ اﻟﺼـﻐﺮ . ﺗﻤﺜـﻞ ﻫـﺬه ا ﺠﺮات ا ﺮاﺣﻞ اﻷوﱃ ﻣـﻦ ﻋﻤﻠﻴـﺔ اﻟﺘﺤـﻮل وﺗﺸ إﱃ أﻧﻪ ﺑﻌﺪ أن ﺗﻘﻮم ا ﺠﺮات اﻟﻀﺨﻤﺔ ا ﺠﺎورة ﺑﺘﺠﺮﻳﺪ ﻫﺬه اﻷﻗﺰام ﻣـﻦ ﻃﺒﻘﺎﺗﻬـﺎ اﻟﺨﺎرﺟﻴﺔ ﻣﻦ اﻟﻨﺠﻮم واﻟﻐﺎز ﻓﺈن ﻣﺎ ﻳﺘﺒﻘـﻰ ﺳﻴﻜﻮن ﻛﺎﺋﻨًﺎ ﻣﻄﺎﺑﻘًﺎ ﻟﻠﻤﺮاﺣﻞ ا ﺘﺄﺧﺮة ﻣﻦ ا ﺠﺮات اﻟﻘﺰﻣـﺔ ﻓﺎﺋﻘـﺔ اﻟﺼـﻐﺮ اﻟﺘـﻲ ﺗـﻢ ﺗﺤﺪﻳﺪﻫﺎ ﺑﺎﻟﻔﻌﻞ . ﻛﻤﺎ وﺟﺪ اﻟﺒﺎﺣﺜﻮن أﻳﻀًـﺎ اﻟﻌﺪﻳﺪ ﻣﻦ اﻷﺟﺮام ذات أﻏﻠﻔﺔ ﻧﺠﻤﻴﺔ ﻣﻤﺘﺪة ـ وﻣﻨﺘ ﴩة ﺟﺪًا ﺣﻮﻟﻬﺎ ﻣﻤﺎ ﻳﺸ إﱃ أﻧﻬﺎ ﺗﻤﺮ ﺣﺎﻟﻴًﺎ ﺑﻤﺮﺣﻠﺔ اﻧﺘﻘﺎﻟﻴـﺔ ﺣﻴـﺚ ﻳـﺘﻢ ﺗﺠﺮﻳـﺪ ﻧﺠﻮﻣﻬﺎ وا ﺎدة ا ﻈﻠﻤﺔ ﻣﻨﻬﺎ . ﻟﻘﺪ ﺣﺪد اﻟﻔﺮﻳﻖ ﺿﻤﻦ ﻋﻴﻨﺔ واﺳﻌﺔ اﻷﺟﺮام ﰲ ﻋﺪة ﻣﺮاﺣﻞ أﺧﺮى ﻣﻦ اﻟﻌﻤﻠﻴﺔ اﻟﺘﻄ ﻮرﻳـﺔ اﻟﺘﻲ ﻋﻨﺪ وﺿﻌﻬﺎ ﺑﺎﻟﺘﺴﻠﺴﻞ ﺗﺤﻜـﻲ ﻗﺼـﺔ ﻣﻘﻨﻌﺔ ﻋﻦ ﻣﻮرﻓﻮﻟﻮﺟﻴـﺎ ا ﺠـﺮات اﻟﻘﺰﻣـﺔ ﻓﺎﺋﻘﺔ اﻟﺼﻐﺮ ﰲ اﻟﻜﻮن . - ﻳﻨﺎﻳﺮ ﻓﺒﺮﺍﻳﺮ 2 0 2 4 [CTIO/NOIRLab/ DOE/NSF/AURA. Image processing: T.A. Rector (University of Alaska An- chorage/NSF’sNOIRLab), M. Zamani (NSF’s NOIRLab), & D. deMartin (NSF’s NOIRLab)].