Free Astronomy Magazine September-October 2025 ARABIC VERSION

SEPTEMBER-OCTOBER2025 UniversityinCanberra. “Usually,the older, thick disk stars are faint, and the young, thin disk stars outshine the entire galaxy. But with Webb’s resolution and unique ability to see through dust and highlight faint old stars, we can identify the two-disk structure of galaxies and measure their thickness separately.” Byanalyzingthese111targetsover cosmological time, the team was able to study single-disk galaxies and double-disk galaxies. Their re- sults indicate that galaxies form a thick disk first, followed by a thin disk.Thetimingofwhenthistakes place is dependent on the galaxy’s mass: high-mass, single-disk galaxies transitioned to two-disk structures around8billionyearsago.Incon- trast, low-mass, single-disk galaxies formed their embedded thin disks later on, about 4 billion years ago. “Thisisthefirsttimeithasbeenpos- sible to resolve thin stellar disks at higher redshift. What’s really novel is uncovering when thin stellar disks starttoemerge,” saidEmilyWis- nioski, a co-author of the paper at the Australian National University in Canberra. “To see thin stellar disks already in place 8 billion years ago, or even earlier, was surprising.” To explain this transition from a sin- gle, thick disk to a thick and thin disk,andthedifferenceintimingfor high- and low-mass galaxies, the team looked beyond their initial edge-on galaxy sample and exam- ined data showing gas in motionfrom the Atacama Large Millime- ter/submillimeter Array (ALMA) and other ground-based surveys. Bytakingintoconsiderationthemo- tion of the galaxies’ gas disks, the team finds their results align with the “turbulent gas disk” scenario, oneofthreemajorhypothesesthat has been proposed to explain the process of thick- and thin-disk for- mation. In this scenario, a turbulent gas disk in the early universe sparks intense star formation, forming a thickstellardisk.Asstarsform,they stabilize the gas disk, which be- comeslessturbulentand,asaresult, thinner.Sincemassivegalaxiescan more efficiently convert gas into stars, they settle sooner than their low-masscounterparts,resultingin the earlier formation of thin disks. Theteamnotesthatthick-andthin- diskformationarenotsiloedevents: Thethickdiskcontinuestogrowas the galaxy develops, though it’s slower than the thin disk’s rate of growth.Webb’s sensitivity is en- abling astronomers to observe smallerandfaintergalaxies,analo- goustoourown,atearlytimesand with unprecedented clarity for the first time. In this study, the team noted that the transition period from thick disk to a thick and thin diskroughlycoincideswiththefor- mationoftheMilkyWaygalaxy’s thin disk. With Webb, astronomers will be able to fur- ther investigate Milky Way-like pro- genitors — galaxies that would have preceded the Milky Way — which could help explain our galaxy’s formation history. In the future, the team intends to in- corporateotherda- ta points into their edge-ongalaxysam- ple. “While this study structurally distin- guishes thin and thick disks, there is still much more we wouldliketoex- plore,” said Tsukui. “ We want to addthetypeofinformationpeople usuallygetfornearbygalaxies,like stellar motion, age, and metallicity. By doing so, we can bridge the in- sights from galaxies near and far, and refine our understanding of diskformation.”  ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 29 ﻋﻨﺪ اﻧﺰﻳﺎح أﺣﻤﺮ أﻋـﲆ . ﻗﺎﻟـﺖ إﻣـﻴﲇ و ﻳـﺲ ﻧﻴﻮﺳﻜﻲ ا ﺆﻟﻔـﺔ ا ﺸـﺎرﻛﺔ ﰲ اﻟﺒﺤـﺚ ﻣـﻦ اﻟﺠﺎﻣﻌ ـﺔ اﻟﻮﻃﻨﻴــﺔ اﻷ ﺳ ـﱰاﻟﻴﺔ ﰲ ﻛ ـﺎﻧﺒ ا : اﻟﺠﺪﻳﺪ " ﻫﻮ اﻛﺘﺸـﺎف ﻣﺘـﻰ ﺗﺒـﺪأ اﻷﻗـﺮاص اﻟﻨﺠﻤﻴﺔ اﻟﺮﻗﻴﻘﺔ ﺑﺎﻟﻈﻬﻮر . إن رؤﻳﺔ أﻗـﺮاص ﻧﺠﻤﻴـﺔ رﻗﻴﻘـﺔ ﻣ ﻮﺟـﻮدة ﺑﺎﻟﻔﻌﻞ ﻗﺒﻞ 8 ﻣﻠﻴﺎرات ﺳﻨﺔ أو ﺣﺘﻰ ﻗﺒﻞ ذﻟﻚ أﻣﺮ ﻣﺜ ﻟﻠﺪﻫﺸﺔ ." ﻟﺘﻔﺴ ﻫﺬا اﻟﺘﺤﻮل ﻣـﻦ ﺑﻔﻀﻞ دﻗﺔ ﺗﻠﺴﻜﻮب وﻳﺐ وﻗﺪرﺗـﻪ اﻟﻔﺮﻳـﺪة ﻋﲆ اﻟﺮؤﻳﺔ ﻋﱪ اﻟﻐﺒﺎر وﺗﺴﻠﻴﻂ ا ﻟﻀـﻮء ﻋـﲆ اﻟﻨﺠﻮم اﻟﻘﺪﻳﻤﺔ اﻟﺨﺎﻓﺘﺔ ﻳ ﻤﻜﻨﻨﺎ ﺗﺤﺪﻳﺪ ﺑﻨﻴـﺔ ا ﺠﺮات ﺛﻨﺎﺋﻴـﺔ اﻷﻗـﺮاص و ﻗﻴـﺎس ﺳـﻤﻜﻬﺎ ﺑﺸﻜﻞ ﻣﻨﻔﺼﻞ . ﺑﺘﺤﻠﻴﻞ ﻫـﺬه اﻷﻫـﺪاف اﻟــ 111 ﻋﲆ ﻣﺪار اﻟﺰﻣﻦ اﻟﻜﻮﻧﻲ ﺗﻤﻜـ ﻦ اﻟﻔﺮﻳـﻖ ﻣﻦ دراﺳﺔ ا ﺠﺮات أﺣﺎدﻳﺔ اﻟﻘﺮص وا ﺠﺮات ﺛﻨﺎﺋﻴﺔ اﻟﻘﺮص ﺗ. ﺸ ﻧﺘﺎﺋﺠﻬﻢ إﱃ أن ا ﺠﺮات ﺗُﺸﻜﻞ ﻗﺮﺻ ﺎً أوﻻً ﺎً ﺳﻤﻴﻜ ﻳﻠﻴﻪ ﻗﺮص رﻗﻴـﻖ . ﻳﻌﺘﻤﺪ ﺗﻮﻗﻴﺖ ﺣﺪوث ذﻟﻚ ﻋﲆ ﻛﺘﻠـﺔ ا ﺠـﺮة : ﻓﻘﺪ اﻧﺘﻘﻠﺖ ا ﺠﺮات أﺣﺎدﻳﺔ اﻟﻘـﺮص ﻋﺎﻟﻴـﺔ اﻟﻜﺘﻠﺔ إﱃ ﻫﻴﺎﻛﻞ ﺛﻨﺎﺋﻴﺔ اﻟﻘﺮصﻣﻨﺬ ﺣـﻮاﱄ 8 ﻣﻠﻴﺎرات ﺳﻨﺔ . ﻋﲆ اﻟﻨﻘﻴﺾ ﻣﻦ ذﻟﻚ ﺷـﻜ ﻠﺖ ا ﺠﺮات أﺣﺎدﻳﺔ اﻟﻘـﺮص ﻣﻨﺨﻔﻀـﺔ اﻟﻜﺘﻠـﺔ أﻗﺮاﺻﻬﺎ اﻟﺮﻗﻴﻘﺔ ا ُﺪﻣﺠﺔ ﻻﺣﻘﺎً ﻣﻨﺬ ﺣﻮاﱄ 4 ﻣﻠﻴﺎرات ﺳﻨﺔ " . ﻫـﺬه ﻫـﻲ ا ـﺮة اﻷوﱃ اﻟﺘـﻲ ﻳُﻤﻜﻦ ﻓﻴﻬﺎ ﺗﺤﺪﻳﺪ اﻷﻗﺮاص اﻟﻨﺠﻤﻴﺔ اﻟ ﺮﻗﻴﻘﺔ ﻋﻨﺪ اﻧﺰﻳﺎح أﺣﻤﺮ أﻋﲆ . ﻗﺎﻟﺖ إﻣـﻴﲇ وﻳـﺲ - أﻣﺮ ﻣﺜ ﻟﻠﺪﻫﺸﺔ ." ﻟﺘﻔﺴ ﻫﺬا اﻟﺘﺤﻮل ﻣـﻦ ﻗ ﺮص واﺣﺪ ﺳﻤﻴﻚ إﱃ ﻗﺮصﺳـﻤﻴﻚ ورﻗﻴـﻖ واﻻﺧﺘﻼف ﰲ اﻟﺘﻮﻗﻴـﺖ ﺑـ ا ﺠـ ﺮات ﻋﺎﻟﻴـﺔ اﻟﻜﺘﻠﺔ وﻣﻨﺨﻔﻀﺔ اﻟﻜﺘﻠﺔ ﻧﻈﺮ اﻟﻔﺮﻳﻖ إﱃ ﻣـﺎ ورا ء ﻋﻴﻨﺔ ا ﺠﺮة اﻷوﻟﻴﺔ ﻣﻦ اﻟﺤﺎﻓﺔ وﻓﺤﺺ ﺑﻴﺎﻧﺎت ﺗ ﻈﻬﺮ ﺣﺮﻛـﺔ اﻟﻐـﺎز ﻣـﻦ ﻣﺼـﻔﻮﻓﺔ أﺗﺎﻛﺎﻣﺎ اﻟﻜﺒـ ة ا ﻠﻴﻤﱰﻳـﺔ / دون ا ﻠﻴﻤﱰﻳـﺔ أ ﺎ) ( وﻏ ﻫﺎ ﻣﻦ ا ﺴﻮ ﺣﺎت اﻷرﺿﻴﺔ . ﺑﺎﺳﺘﻌﺮاض ﺣﺮﻛﺔ أﻗﺮاص ﻏﺎز ا ﺠﺮات وﺟﺪ اﻟﻔﺮﻳﻖ أن ﻧﺘـﺎﺋﺠﻬﻢ ﺗﺘﻮاﻓـﻖ ﻣـﻊ ﺳـﻴﻨﺎرﻳﻮ " ﻗﺮص اﻟﻐﺎز ا ﻀ "ﻄﺮب وﻫﻮ أﺣﺪ اﻟﻔﺮﺿﻴﺎت اﻟﺮﺋﻴﺴﻴﺔ اﻟﺜﻼث اﻟﺘﻲ ﻃ ﺮﺣﺖ ﻟﺘﻔﺴ ﻋﻤﻠﻴﺔ ﺗﻜﻮﻳﻦ اﻷﻗﺮاص اﻟﺴ ﻤﻴﻜﺔ واﻟﺮﻗﻴﻘﺔ ﰲ ﻫـﺬا و اﻟﺴﻴﻨﺎرﻳﻮ ﻳ ﺜـ ﻗـﺮص اﻟ ا ﻐـﺎز ﰲ ﻀـﻄﺮب اﻟﻜﻮن ا ﺒﻜﺮ ﻋﻤﻠﻴﺔ ﺗﻜـﻮﻳﻦ ﻧﺠﻤـﻲ ﻣ ﻜﺜﻔـﺔ ﻣﻜﻮﻧﺎً ﻗﺮﺻﺎً ﻧﺠﻤﻴﺎً ﺳﻤﻴﻜﺎً وﻋﻨﺪﻣﺎ ﺗﺘﺸـﻜﻞ اﻟﻨﺠﻮم ﻓﺈﻧﻬﺎ ﺗُﺜﺒ ﺖ ﻗﺮص اﻟﻐﺎز اﻟﺬي ﻳ ﺼـﺒﺢ أﻗــﻞ ا ﺿــﻄﺮاﺑًﺎ، وﺑﺎﻟﺘــﺎﱄ أرق . وﻧﻈــﺮًا ﻷن أﻗﻞ اﺿﻄﺮاﺑﺎً ﻣﻊ ﺗﻄﻮر ا ﺠﺮة ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أﻧﻪ أ ﺑﻄﺄ ﻣﻦ ﻣﻌﺪل ﻧﻤﻮ اﻟﻘـﺮص اﻟﺮﻗﻴـﻖ إن. ﺣﺴﺎﺳﻴﺔ ﺗﻠﺴﻜﻮب وﻳﺐ ﺗﻤﻜﻦ ﻋﻠﻤﺎء اﻟﻔﻠـ ﻚ ﻣﻦ رﺻـﺪ ﻣﺠـﺮات ﺑﻴﻨﻴـﺔ أﺻـﻐﺮ وأﺿـﻌﻒ ﻣﻤﺎﺛﻠﺔ ﺠﺮاﺗﻨﺎ ﰲ اﻟﻌﺼﻮر ا ﺒﻜﺮة وﺑﻮﺿﻮح ﻏ ﻣﺴﺒﻮق ﻷول ﻣﺮة . رﺻﺪ اﻟﻔﺮﻳﻖ ﰲ ﻫـﺬه اﻟﺪراﺳﺔ أن ﻓﱰة اﻻﻧﺘﻘﺎل ﻣﻦ اﻟﻘﺮص اﻟ ﺴﻤﻴﻚ إﱃ اﻟ ﻘﺮص اﻟﺴﻤﻴﻚ واﻟﺮﻗﻴﻖ ﺗﺘـﺰاﻣﻦ ﺗﻘﺮﻳﺒـ ﺎً ﻣﻊ ﺗﻜﻮﻳﻦ اﻟﻘﺮص اﻟﺮﻗﻴﻖ ﺠﺮة درب اﻟﺘﺒﺎﻧﺔ . ﻳﺸ ﻫـﺬا اﻻﻛﺘﺸـﺎف إﱃ أن ا ﺠـﺮات اﻷوﱃ ﻛ ﺎﻧﺖ أﻛﺜﺮ ﻧﺸـﺎﻃًﺎ ﰲ ﺗﻜـﻮﻳﻦ اﻟﻨﺠـﻮم ﻣﻤـﺎ ﺳﻤﺢ ﻟﻬﺎ ﺑﺘﻄﻮﻳﺮ أﻗﺮاﺻﻬﺎ اﻟﺴﻤﻴﻜﺔ ﺑﴪﻋﺔ أﻛﱪ . ﺑﺎﺳـﺘﺨﺪام ﺗﻠﺴـﻜﻮب وﻳـﺐ ﺳـﻴﺘﻤﻜﻦ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻣﻦ ﻣﻮاﺻـﻠﺔ دراﺳـﺔ ا ﺠـﺮات اﻻوﻟﻴﺔ اﻟﺸﺒﻴﻬﺔ ﺑﺪرب اﻟﺘﺒﺎﻧﺔ - ا ﺠﺮات اﻟﺘﻲ ﺳﺒﻘﺖ درب اﻟﺘﺒﺎﻧﺔ - واﻟﺘﻲ ﻳﻤﻜﻦ أن ﺗﺴﺎﻋﺪ ﰲ ﺗﻔﺴ ﺗﺎرﻳﺦ ﺗﻜﻮﻳﻦ ﻣﺠﺮﺗﻨﺎ . ﻳﺘﻮﻗﻊ أن ﻳﺘﻤﻜﻦ اﻟﻔﺮﻳـﻖ ﰲ ا ﺴ ـﺘﻘﺒﻞ ﻣ ـﻦ دﻣ ـﺞ ﻧﻘـﺎط ﺑﻴﺎﻧـﺎت أﺧـﺮى ﰲ ﻋﻴﻨﺔ ا ﺠﺮة ﻋﲆ اﻟﺤﺎﻓـﺔ . وﺗﻌﺘـﺰم اﻟـ ﺔ دﻣـﺞ ﴩﻛ ـ ﻧﻘـﺎط ﺑﻴﺎﻧـﺎت أﺧـﺮى ﰲ ﻋﻴﻨﺔ ا ﺠﺮة ﻋ . ﲆ اﻟﺤﺎﻓـﺔ ﻗـﺎل ﺗﺴـﻮﻛﻮي " : ﺑﻴﻨﻤـﺎ ﺗﻤﻴ ﺰ ﻫﺬه اﻟﺪراﺳﺔ ﻫﻴﻜﻠﻴ ﺎً ﺑ ـ اﻷﻗ ـﺮاص اﻟﺮﻗﻴﻘ ـﺔ واﻟﺴﻤﻴﻜﺔ ﻻ ﻳﺰال ﻫﻨـﺎك اﻟﻜﺜـــ ﻣﻤـــﺎ ﻧـــﻮد اﺳﺘﻜﺸﺎﻓﻪ . ﻧﺮﻳﺪ إﺿـﺎﻓﺔ ﻧﻮع ا ﻌﻠﻮﻣﺎت اﻟﺘﻲ ﻳﻬﺘﻢ ﺑﻬ ـﺎ اﻟﻨ ـﺎس ﻋـﺎدةً ﻋـﻦ ا ﺠ ـﺮات اﻟﻘﺮﻳﺒ ـﺔ ﻣﺜ ـﻞ ﺣﺮﻛ ﺔ اﻟﻨﺠـﻮم وﻋﻤﺮﻫـﺎ وﻣﻌﺪﻧﻬﺎ ﻣﻦ ﺧﻼل دﻣـﺞ ﻫﺬه اﻟﺒﻴﺎﻧﺎت ﻳﻤﻜﻨﻨﺎ ﺑﻨﺎء ﺻــﻮرة أﻛﺜــﺮ اﻛﺘﻤــﺎﻻً ﻟﺘﺎرﻳﺦ ﺗﻄـﻮر ا ﺠـﺮات . اﺿﻄﺮاﺑ ﺎً وﺑﺎﻟﺘـﺎﱄ أرق وﻧﻈـﺮ اً ﻷن ا ﺠـﺮات اﻟﻀﺨﻤﺔ ﻳﻤﻜﻨﻬﺎ ﺗﺤﻮﻳـﻞ اﻟﻐـﺎز ﺑﻜﻔـﺎءة إﱃ ﻧﺠﻮم ﻓﺈﻧﻬـﺎ ﺗﺴـﺘﻘﺮ أﴎع ﻣـﻦ ﻧﻈ اﺗﻬـﺎ ﻣﻨﺨﻔﻀﺔ اﻟﻜﺘﻠﺔ ﺆ ﻣﻤﺎ ﻳ دي إﱃ ﺗﻜﻮﻳﻦ ﻣﺒﻜـﺮ ﻷﻗﺮاص رﻗﻴﻘﺔ وﻳﺸ اﻟﻔﺮﻳﻖ إﱃ أن ﺗﻜـﻮﻳﻦ اﻷﻗﺮاص اﻟﺴﻤﻴﻜﺔ واﻟﺮﻗﻴﻘـﺔ ﻟﻴﺴـﺎ ﺣـﺪﺛ ﻣﻨﻔﺼﻠ : ﻳﺴﺘﻤﺮ اﻟﻘﺮص اﻟﺴﻤﻴﻚ ﰲ اﻟﻨﻤـﻮ ﻣﻊ ﺗﻄﻮر ا ﺠﺮة، ﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أﻧﻪ أﺑﻄﺄ ﻣﻦ ﻣﻌﺪل ﻧﻤﻮ اﻟﻘﺮص اﻟﺮﻗﻴﻖ . ﺗُﻤﻜّﻦ ﺣﺴﺎﺳـﻴﺔ ﻟﺘﺎرﻳﺦ ﺗﻄﻮر ا ﺠـﺮا . ت ﺳـﻴﻤﻜﻨﻨﺎ ذﻟـﻚ ﻣـﻦ ﺗﺘﺒﻊ ﻛﻴﻔﻴﺔ ﺗ ﺸﻜﻞ اﻷﻗﺮاص وﺗﻐ ﻫﺎ ﺑﻤـﺮور اﻟﻮﻗﺖ ﻣﻤﺎ ﻳﺘﻴﺢ ﻟﻨﺎ ﻓﻬﻤ ﺎ أﻋﻤﻖ ﻟﺘﺎرﻳﺦ ﻣﺠﺮة درب اﻟ ﺘﺒﺎﻧ ـﺔ وا ﺠ ـﺮات اﻷﺧــﺮى ﰲ اﻟﻜــﻮن وﺗﻄﻮرﻫﺎ ﻋﱪ اﻟﻌﺼﻮر اﻟﻜﻮﻧﻴﺔ ﻳ وﺑﺬﻟﻚ ﻤﻜﻨﻨﺎ رﺑﻂ ا ﻌﻠﻮ ﻣﺎت ﻣﻦ ا ﺠﺮات اﻟﻘﺮﻳﺒﺔ واﻟﺒﻌﻴﺪة وﺗﺤﺴ ﻓﻬﻤﻨﺎ ﻟﺘﻜﻮﻳﻦ اﻷﻗﺮا .ص اﻟﻤﺠﺮات ذات اﻟﻘﺮص اﻟﺴﻤ ﻚ ﻓﻘﻂ ﺳﺒﺘﻤﺒﺮ - ﺃﻛﺘﻮﺑﺮ 2 0 2 5