Free Astronomy Magazine September-October 2023 ARABIC VERSION

Revealing the hidden seeds of giant stars bALMA Observatory Nicolás Lira sing the Atacama Large Mil- limeter/submillimeter Array (ALMA), an international re- search team led by Kaho Morii, Patricio Sanhueza, and Fumitaka Nakamura has made a pioneering discovery, unveiling over 800 “stellar seeds” nestled within massive cos- mic clouds. These insights are mon- umental in decoding the enigmatic process of high-mass star formation, an essential cog in generating life’s building blocks. ALMA’s state-of-the- art sensitivity and resolution proved pivotal in shedding light on this mys- tery. The researchers used ALMA to peer into 39 massive cosmic clouds, known as Infrared Dark Clouds (IRDCs), believed to be the nurseries of high-mass stars. With ALMA’s capabilities, over 800 stellar seeds, or molecular cloud cores, were identified within these clouds, making it the most extensive sample ever discovered. Astound- ingly, 99% of these seeds lack the mass typically thought necessary to grow into high-mass stars. This groundbreaking observation indi- cates that high-mass stars might fol- low a different growth trajectory than smaller stars. Moreover, it was observed that core density, rather than mass, may be the critical factor in high-mass star formation. Kaho Morii, a graduate student at the University of Tokyo, shared, “We have shown with more certainty than previous studies that high-mass stars have a different growth sce- nario from low-mass stars. Also, we can infer that denser cores in clus- ters may grow up more efficiently by accumulating surrounding materi- als. It seems that the environment of dense material is more important than the original mass for massive stars formation.” Patricio Sanhueza of the National Astronomical Observatory of Japan 26 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ اﻟﻜﺸﻒﻋﻦ اﻟ ﺬوراﻟ ـ ﺨﻔ ﺔ ﻟﻠﻨﺠﻮم اﻟﻌﻤﻼﻗﺔ : ﻘﻠﻢ ﻧﻴ ﻮﻻس ﻟ ا ﻣﺮ - ﺻﺪ أﻟﻤﺎ ﺑﺎﺳ ــــ ﺘﺨﺪام ﺔ ﻣﺼــﻔﻮﻓ ﻣﺮﺻـﺪ أﺗﻜ ﺎﻣـﺎ ا ﻠﻴﻤﱰي / ﺗﺤﺖ ا ﻠﻴﻤﱰي اﻟﻜﺒ ( أ ﺎ) ﺣﻘﻖ ﻓﺮﻳـﻖ ﺑﺤـﺚ دوﱄ ﺑﻘﻴـﺎدة ﻛـﺎﻫﻮ ﻣـﻮري وﺑﺎﺗﺮﻳﺴ ــﻴﻮ ﺳـــﺎﻧﻬﻮﻳﺰا و وﻓﻮ ﻣﻴﺘﺎﻛـــﺎ ﻧﺎﻛﺎﻣﻮرا اﻛﺘﺸﺎﻓﺎً ﻣﻬﻤﺎً ﺣﻴﺚ ﻛﺸﻒ اﻟﻨﻘﺎب ﻋﻦ أﻛﺜﺮ ﻣﻦ 800 " ﺑﺬور ﻧﺠﻤﻴﺔ " ﺗﻘﻊ داﺧﻞ ﺳﺤﺐ ﻛﻮﻧﻴﺔ ﺿﺨﻤﺔ . ﺗﻌﺘﱪ ﻫـﺬه اﻷﻓﻜـﺎر ﻫﺎﺋﻠﺔ ﰲ ﻓﻚ رﻣﻮز اﻟﻌﻤﻠﻴﺔ اﻟﻐ ﺎﻣﻀﺔ ﻟﺘﻜﻮﻳﻦ اﻟﻨﺠﻮم ﻋﺎﻟﻴﺔ اﻟﻜﺘﻠﺔ وﻫﻲ ﻗﺎﻋﺪة ﰲ ﻫﺎﻣـﺔ ﺗﻮﻟﻴﺪ اﻟﻠﺒﻨﺎت اﻷﺳﺎﺳﻴﺔ ﻟﻠﺤﻴﺎة وﻗـﺪ أﺛﺒﺘـﺖ ﺣﺴﺎﺳ ـﻴﺔ ﻣﺮﺻ ـﺪ أ ـﺎ ا ﺘﻄ ـﻮرة ودﻗ ـﺔ وﺿﻮﺣﻬﺎ دورﻫﺎ ا ﺤﻮري ﰲ ﺗﺴﻠﻴﻂ اﻟﻀﻮء ﻋﲆ ﻫﺬا اﻟﻠﻐﺰ . اﺳﺘﺨﺪم اﻟﺒﺎﺣﺜﻮن ﻣﺮﺻﺪ أ ﺎ ﻟﻠﻨﻈﺮ ﰲ 39 ﺳﺤﺎﺑﺔ ﻛﻮﻧﻴﺔ ﺿﺨﻤﺔ ﺗُﻌـﺮف ﺑﺎﺳـﻢ اﻟﺴـﺤﺐ ا ﻈﻠﻤـﺔ ﺑﺎﻷﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤــﺮاء ) IRDCs ( واﻟﺘــﻲ ﻳُﻌﺘﻘــﺪ أﻧﻬــﺎ اﻟﺤﺎﺿـﻨﺎت ﻟ ﻠﻨﺠـﻮم ذات اﻟﻜﺘﻠـﺔ اﻟﻌﺎﻟﻴـﺔ وﺑﻔﻀﻞ ﻗﺪرات ﻣﺮﺻﺪ أ ﺎ ﺗﻢ ﺗﺤﺪﻳـﺪ أﻛﺜـﺮ ﻣﻦ 800 ﺑـﺬرة ﻧﺠﻤﻴـﺔ أو أﻧﻮﻳـﺔ ﺳـﺤﺎﺑﺔ ﺟﺰﻳﺌﻴﺔ داﺧﻞ ﻫﺬه اﻟﺴـﺤﺐ ﻣﻤـﺎ ﻳﺠﻌﻠﻬـﺎ اﻟﻌﻴﻨﺔ اﻷﻛﺜﺮ ﺷﻤﻮﻻً اﻟﺘﻲ ﺗﻢ اﻛﺘﺸﺎﻓﻬﺎ ﻋﲆ اﻹﻃﻼق وﻣﻦ ا ﺜ ﻟﻠﺪﻫﺸـﺔ أن 99 % ﻣـﻦ ﻫﺬه اﻟﺒﺬور ﺗﻔﺘﻘﺮ إﱃ اﻟﻜﺘﻠـﺔ اﻟﺘـﻲ ﻳُﻌﺘﻘـﺪ ﻋﺎد ةً أﻧﻬﺎ ﴐورﻳﺔ ﻟﺘﻨﻤﻮ ﻟﺘﺼـﺒﺢ ﻧﺠﻮﻣـ ﺎً ﻋﺎﻟﻴﺔ اﻟﻜﺘﻠﺔ . ﺗﺸ ﻫﺬه اﻷرﺻﺎد اﻟﺮاﺋﺪة إﱃ أن اﻟﻨﺠﻮم ذات اﻟﻜﺘﻠﺔ اﻟﻌﺎﻟﻴﺔ ﻗﺪ ﺗﺘﺒﻊ ﻣﺴ ﺎر ﻧﻤﻮ ﻣﺨﺘﻠﻒ ﻋﻦ اﻟﻨﺠﻮم اﻷﺻﻐﺮ ﻋﻼوة ﻋﲆ ذﻟﻚ ﻓﻘﺪ ﻟـﻮﺣﻆ أن ﻛﺜﺎﻓـﺔ اﻟﻨـﻮاة وﻟـﻴﺲ اﻟﻜﺘﻠﺔ ﻗﺪ ﺗﻜﻮن اﻟﻌﺎﻣﻞ اﻟﺤﺎﺳﻢ ﰲ ﺗﻜـﻮﻳﻦ ـــ اﻟﻨﺠﻮم ﻋﺎﻟﻴﺔ اﻟﻜﺘﻠﺔ . ﻗﺎل ﻛﺎﻫﻮ ﻣﻮري وﻫﻮ ﻃﺎﻟﺐ دراﺳـﺎت ﻋﻠﻴـﺎ ﰲ ﺟﺎﻣﻌـﺔ ﻃﻮﻛﻴـﻮ : " ﻟﻘﺪ أﻇﻬﺮﻧﺎ ﺑﻘﺪر أﻛـﱪ ﻣـﻦ اﻟﻴﻘـ ﻣـﻦ اﻟﺪراﺳﺎت اﻟﺴﺎﺑﻘﺔ أن اﻟﻨﺠـﻮم ذات اﻟﻜﺘﻠـﺔ اﻟﻌﺎﻟﻴﺔ ﻟﺪﻳﻬﺎ ﺳﻴﻨﺎرﻳﻮ ﻧﻤـﻮ ﻣﺨﺘﻠـﻒ ﻋـﻦ ــــ اﻟﻨﺠﻮم ﻣﻨﺨﻔﻀـﺔ اﻟﻜﺘﻠـﺔ . وﻳﻤﻜﻨﻨـﺎ اﻟﻨﺠﻮم ﻣﻨﺨﻔﻀﺔ اﻟﻜﺘﻠﺔ وﻳﻤﻜـﻦ أﻳﻀـﺎً أن ﻧﺴﺘﻨﺘﺞ أن اﻟﻨﻮى اﻷﻛﺜﺮ ﻛﺜﺎﻓﺔ ﰲ اﻟﻌﻨﺎﻗﻴـﺪ ﺗﻨﻤﻮ ﺑﻜﻔﺎءة أﻛﱪ ﻋﱪ ﺗﺮاﻛﻢ ا ﻮاد ا ﺤﻴﻄﺔ وﻳﺒﺪو أن ﺑﻴﺌﺔ ا ﺎدة اﻟﻜﺜﻴﻔﺔ أﻛﺜﺮ أﻫﻤﻴﺔ ﻣﻦ اﻟﻜﺘﻠﺔ اﻷﺻﻠﻴﺔ ﻟﺘﻜـﻮﻳﻦ اﻟﻨﺠـﻮم اﻟﻀـﺨﻤﺔ - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 3 ﺎﺳﺘﺨﺪام