Free Astronomy Magazine November-December 2022 ARABIC VERSION

the Gemini South telescope of the International Gemini Observatory, operated by NSF’s NOIRLab, as- tronomers have obtained the sharpest-ever image of R136a1 — the most massive known star. This colossal star is a member of the R136 star cluster, which lies about 160,000 light-years from Earth in the center of the Tarantula Nebula in the Large Magellanic Cloud, a dwarf companion galaxy of the Milky Way. Previous observations suggested that R136a1 had a mass somewhere between 250 to 320 times the mass of the Sun. The new Zorro observa- tions, however, indicate that this giant star may be only 170 to 230 times the mass of the Sun. Even with this lower estimate, R136a1 still qualifies as the most massive known star. Astronomers are able to estimate a star’s mass by comparing its ob- served brightness and temperature with theoretical predictions. The sharper Zorro image allowed NSF’s NOIRLab astronomer Venu M. Kalari and his colleagues to more accurately separated the brightness of R136a1 from its nearby stellar companions, which led to a lower estimate of its brightness and therefore its mass. “Our results show us that the most massive star we currently know is not as massive as we had previously thought,” explained Kalari, lead author of the paper announcing this result. “This suggests that the upper limit on stellar masses may also be smaller than previously thought.” This result also has implications for the origin of elements heavier than helium in the Universe. These ele- ments are created during the cata- clysmicly explosive death of stars more than 150 times the mass of the Sun in events that astronomers refer to as pair-instability super- ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ٤٧ ﺣﺼﻞ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻋﲆ أوﺿﺢ ﺻـﻮرة ﻋـﲆ اﻹﻃﻼق ﻟــ R136a1 ، وﻫـﻮ أﺿـﺨﻢ ﻧﺠـﻢ . ﻣﻌﺮوف ﻫﺬا اﻟﻨﺠﻢ اﻟﻀـﺨﻢ ﻫـﻮ ﻋﻀـﻮ ﰲ ﻋﻨﻘﻮد ﻧﺠﻮم R136 اﻟﺘﻲ ﺗﻘﻊ ﻋﲆ ﺑﻌﺪ ﺣﻮاﱄ ١٦٠ أﻟﻒ ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﻣـﻦ اﻷرض ﰲ ﻣﺮﻛـﺰ ﺳﺪﻳﻢ اﻟﺮﺗﻴﻼء ﰲ ﺳـﺤﺎﺑﺔ ﻣـﺎﺟﻼن اﻟﻜﺒـ ة وﻫﻲ ﻣﺠـﺮة ﻗﺰﻣـﺔ ﻣ ﺼـﺎﺣﺒﺔ ﺠـﺮة درب اﻟﺘﺒﺎﻧﺔ . أﺷﺎرت اﻷرﺻﺎد اﻟﺴﺎﺑﻘﺔ إﱃ أن ﻛﺘﻠﺔ ﻋﻨﻘﻮد R136a1 ﺗـﱰاوح ﺑـ ٢٥٠ إﱃ ٣٢٠ ﺿﻌﻒ ﻛﺘﻠﺔ اﻟﺸﻤﺲ . وﻣﻊ ذﻟﻚ ، ﻓﺈن أرﺻﺎد ﺟﻬﺎز اﻟﺘﺼﻮﻳﺮ Zorro اﻟﺠﺪﻳﺪة ﺗﺸـ إﱃ أن ﻫﺬا اﻟﻨﺠﻢ اﻟﻌﻤﻼق ﻗﺪ ﺗﻜﻮن ﻛﺘﻠﺘـﻪ ١٧٠ إﱃ ٢٣٠ ﺿﻌﻒ ﻛﺘﻠﺔ اﻟﺸﻤﺲ ﻓﻘﻂ . ﺣﺘـﻰ ﻣـﻊ ﻫﺬا اﻟﺘﻘﺪﻳﺮ ا ـﻨﺨﻔﺾ ، ﻻ ﻳـﺰ ال R136a1 ﻣﺆﻫﻼً ﻟﻴﻜﻮن أﺿﺨﻢ ﻧﺠﻢ ﻣﻌﺮوف . ﻳﺴﺘﻄﻴﻊ اﻟﻔﻠﻜﻴﻮن ﺗﻘﺪﻳﺮ ﻛﺘﻠﺔ اﻟﻨﺠﻢ ﺑﻤﻘﺎرﻧﺔ ﻌﺎﻧـﻪ ﻣـﻊ درﺟـﺔ ﺣﺮارﺗـﻪ ﺑﺎﻟﺘﻮﻗﻌـﺎت اﻟﻨﻈﺮﻳـﺔ . ﺳﻤﺤﺖ ﺻﻮرة Zorro اﻷﻛﺜﺮ وﺿﻮﺣًﺎ ﻟﻌـﺎﻟﻢ اﻟﻔﻠﻚ ﻓﻴﻨﻮ ﻛﺎﻻري وزﻣﻼؤه ﺑﻔﺼﻞ ﺳـﻄﻮع اﻟـﻨﺠﻢ R136a1 ﺑﺪﻗـﺔ أﻛـﱪ ﻋـﻦ رﻓﺎﻗـﻪ اﻟﻨﺠﻤﻴ اﻟﻘﺮﻳﺒ ، ﻣﻤﺎ أدى إﱃ ﺗﻘﺪﻳﺮ أﻗـﻞ ﻟﺴﻄﻮﻋﻪ وﺑﺎﻟﺘﺎﱄ ﻛﺘﻠﺘﻪ . أوﺿﺢ ﻛﺎﻻري ا ﺆﻟﻒ اﻟﺮﺋﻴﴘ ﻟﻠﻮرﻗﺔ اﻟﺘـﻲ أﻋﻠﻨﺖ ﻋﻦ ﻫﺬه اﻟﻨﺘﻴﺠﺔ " : ﺗﻈﻬﺮ ﻟﻨﺎ ﻧﺘﺎﺋﺠﻨـﺎ أن أﺿﺨﻢ ﻧﺠﻢ ﻧﻌﺮﻓﻪ ﺣﺎﻟﻴًﺎ ﻟﻴﺲ ﺑﺎﻟﻀﺨﺎﻣﺔ اﻟﺘﻲ ﻛﻨﺎ ﻧﻌﺘﻘﺪﻫﺎ ﺳﺎﺑﻘًﺎ " ." ﻫﺬا ﻳﺸ إﱃ أن اﻟﺤﺪ اﻷﻋﲆ ﻟﻠﻜﺘﻞ اﻟﻨﺠﻤﻴﺔ ﻗﺪ ﻳﻜـﻮن أﻳﻀًـﺎ أﺻﻐﺮ ﻣﻤﺎ ﻛﺎن ﻳﻌﺘﻘﺪ ﺳﺎ ." ﺑﻘًﺎ ﻫﺬه اﻟﻨﺘﻴﺠﺔ ﻟﻬﺎ أﻳﻀًﺎ آﺛﺎر ﻋﲆ أﺻﻞ اﻟﻌﻨﺎﴏ اﻷﺛﻘﻞ ﻣـﻦ اﻟﻬﻠﻴﻮم . ﰲ اﻟﻜﻮن ﺗﺘﺸﻜﻞ ﻫﺬه اﻟﻌﻨﺎﴏ أ ﺛﻨﺎء ا ﻮت اﻟﻔﺠﺎﺋﻲ ا ﺘﻔﺠﺮ ﻟﻠﻨﺠـﻮم اﻟﺘـﻲ ﺗﺰﻳـﺪ ﻛﺘﻠﺘﻬﺎ ﻋـﻦ ١٥٠ ﺿـﻌﻒ ﻛﺘﻠـﺔ اﻟﺸـﻤﺲ ﰲ اﻷﺣﺪاث اﻟﺘﻲ ﻳﺸ إﻟﻴﻬﺎ ﻋﻠﻤﺎء اﻟﻔﻠـﻚ ﻋـﲆ أﻧﻬﺎ ﻣﺴﺘﻌﺮات ﻋﻈﻤﻰ ﺛﻨﺎﺋﻴﺔ . ﻣﻀﻄﺮﺑﺔ ﻧﻮﻓﻤ دﻳﺴﻤ 2022