Free Astronomy Magazine September-October 2023 ARABIC VERSION

Never-before-seen way to annihilate a star by NOIRLab − Charles Blue ost stars in the Universe die in predictable ways, de- pending on their mass. Rel- atively low-mass stars like our Sun slough off their outer layers in old age and eventually fade to become white dwarf stars. More massive stars burn brighter and die sooner in cataclysmic supernova explosions, creating ultradense objects like neu- tron stars and black holes. If two such stellar remnants form a binary system, they also can eventually col- lide. New research, however, points to a long-hypothesized, but never- before-seen, fourth option. While searching for the origins of a long-duration gamma-ray burst (GRB), astronomers using the Gemini South telescope in Chile, part of the International Gemini Observatory operated by NSF’s NOIRLab, and other telescopes, have uncovered evidence of a demolition-derby-like collision of stars or stellar remnants in the chaotic and densely packed region near an ancient galaxy’s su- permassive black hole. “These new results show that stars can meet their demise in some of the densest regions of the Universe where they can be driven to col- lide,” said Andrew Levan, an as- tronomer with Radboud University in The Netherlands and lead author of a paper appearing in the journal Nature Astronomy. “This is exciting for understanding how stars die and for answering other questions, such as what unexpected sources might create gravitational waves that we could detect on Earth.” Ancient galaxies are long past their star-forming prime and would have few, if any, remaining giant stars, the principal source of long GRBs. Their cores, however, are teeming with stars and a menagerie of ultra- dense stellar remnants, such as white dwarf stars, neutron stars, and black holes. Astronomers have long suspected that in the turbulent bee- hive of activity surrounding a super- massive black hole, it would only be a matter of time until two stellar ob- jects collide to produce a GRB. Evi- dence for that type of merger, how- ever, has been elusive. The first hints that such an event had occurred were seen on 19 Octo- ber 2019 when NASA’s Neil Gehrels ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 34 ﻃﺮ ﻘــــــــﺔ ﻟــــــــﻢ ﺴــــــــﺒﻖ ﻟﻬــــــــﺎ ﻣﺜﻴﻞﻹ ﺎدة اﻟﻨﺠﻮم : ﻘﻠﻢ ﺗﺸﺎرﻟﺰ ﻠﻮ - ﻣﺨﺘ ﻧﻮﻳﺮﻻب إﻧـ ﻣﻌﻈﻢ اﻟﻨﺠﻮم ﰲ اﻟﻜﻮن ﺗﻤـﻮت ﺑﻄـﺮق ﻳﻤﻜـﻦ اﻟﺘﻨﺒـﺆ ﺑﻬـﺎ اﻋﺘﻤـﺎدا ﻋـﲆ ﻛﺘﻠﺘﻬـﺎ . اﻟﻨﺠﻮم ذات اﻟﻜﺘﻠﺔ ا ﻨﺨﻔﻀﺔ ﻧﺴـﺒﻴ ﺎً ﻣﺜـﻞ ﺷﻤﺴﻨﺎ ﺗﺘﺨﻠﺺ ﻣﻦ ﻃﺒﻘﺎﺗﻬﺎ اﻟﺨﺎرﺟﻴﺔ ﰲ ﺳﻦ اﻟﺸﻴﺨﻮﺧﺔ وﺗﺘﻼﳽ ﰲ اﻟﻨﻬﺎﻳﺔ ﻟﺘﺼﺒﺢ ﺎً ﻣ ﻧﺠﻮ ﻗﺰﻣﺔ ﺑﻴﻀـﺎء . ا ﺰﻳـﺪ ﻣـﻦ اﻟﻨ ﺠـﻮم اﻟﻀــﺨﻤﺔ ﺗﺤـﱰق ﺑﺸـﻜﻞ أﻛﺜـﺮ ﺳـﻄﻮﻋ ﺎً وﺗﻤـﻮت ﻋـﺎﺟﻼً ﰲ اﻧﻔﺠـﺎرات ا ﺴـﺘﻌﺮات اﻟﻌﻈﻤﻰ ) اﻟﺴﻮﺑﺮﻧﻮﻓﺎ ( اﻟﻜﺎرﺛﻴﺔ ﻣﻤﺎ ﻳﺨﻠﻖ اﺟﺮاﻣــﺎً ﻓﺎﺋﻘــﺔ اﻟﻜﺜﺎﻓــﺔ ﻣﺜــﻞ اﻟﻨﺠــﻮم اﻟﻨﻴﻮﺗﺮوﻧﻴﺔ واﻟﺜﻘـﻮب اﻟﺴـﻮداء . إذا ﺷـﻜﻞ اﺛ ﻨﺎن ﻣﻦ ﻫﺬه اﻟﺒﻘﺎﻳﺎ اﻟﻨﺠﻤﻴﺔ ﻧﻈﺎﻣ ﺎً ﺛﻨﺎﺋﻴﺎً ﻓﻤﻦ ا ﻤﻜﻦ أﻳﻀﺎً أن ﻳﺘﺼـﺎدﻣﺎ ﰲ اﻟﻨﻬﺎﻳـﺔ وﻣﻊ ذﻟﻚ، ﺗﺸ اﻷﺑﺤﺎث اﻟﺠﺪﻳﺪة إﱃ ﺧﻴـﺎر راﺑﻊ ﺗﻢ اﻓﱰاﺿﻪ ﻣﻨﺬ ﻓﱰة ﻃﻮﻳﻠﺔ وﻟﻜﻦ ﻟﻢ ﻳﺴﺒﻖ ﻟﻪ ﻣﺜﻴﻞ . أﺛﻨـﺎء اﻟﺒﺤـﺚ ﻋـﻦ أﺻـﻮل اﻧﻔﺠﺎر أﺷﻌﺔ ﻏﺎﻣﺎ اﻛﺘﺸﻒ ﻋﻠﻤـﺎء اﻟﻔﻠـﻚ ﺑﺎﺳـﺘﺨﺪ ام ﺗﻠﺴـﻜﻮب ﺟﻴﻤﻴﻨـﻲ ﺳـﺎوث ﰲ ﺗﺸﻴﲇ وﻫﻮ ﺟﺰء ﻣﻦ ﻣﺮﺻﺪ ﺟﻴﻤﻴﻨﻲ اﻟﺪوﱄ اﻟﺬي ﻳﺪﻳﺮه ﻣﺨﺘﱪ ﻧﻮﻳﺮﻻب اﻟﺘﺎﺑﻊ ﺆﺳﺴـﺔ اﻟﻌﻠـﻮم اﻟﻮﻃﻨﻴـﺔ اﻷﻣﺮﻳﻜﻴـﺔ وﺗﻠﺴـﻜﻮﺑﺎت أﺧﺮى أدﻟﺔ ﻋﲆ ﺣﺪوث دﻳﺮﺑﻲ ﻫـﺪم ﻳﺸـﺒﻪ اﺻـﻄﺪام اﻟﻨﺠـﻮم أو اﻟﺒﻘﺎﻳـﺎ اﻟﻨﺠﻤﻴ ـﺔ ﰲ ﻣﻨﻄﻘــﺔ ﻓﻮﺿـﻮﻳﺔ وﻣﻜﺘﻈ ـﺔ ﺑﺎﻷﺟﺴ ـﺎم ﺑﺎﻟﻘﺮب ﻣﻦ ﺛﻘـﺐ أﺳـﻮد ﻫﺎﺋـﻞ ﰲ ﻣﺠـﺮة . ﻗﺪﻳﻤـﺔ ﻗـﺎل أﻧـﺪرو ﻟﻴﻔـﺎن ﻋـﺎﻟﻢ اﻟﻔﻠـﻚ ﺑﺠﺎﻣﻌﺔ رادﺑﻮد ﰲ ﻫﻮﻟﻨﺪا وا ﺆﻟﻒ اﻟﺮﺋ ﻴﴘ ـ ﻟﻮرﻗﺔ ﺑﺤﺜﻴـﺔ ﻧــﴩت ﰲ ﻣﺠﻠـﺔ ﻧﻴﺘــﴩ اﺳﱰوﻧﻮﻣﻲ :" ﺗﻈﻬﺮ ﻫﺬه اﻟﻨﺘﺎﺋﺞ اﻟﺠﺪﻳـﺪة أن اﻟﻨﺠﻮم ﻳﻤﻜﻦ أن ﺗﻮاﺟﻪ زواﻟﻬﺎ ﰲ ﺑﻌـﺾ ا ﻨﺎﻃﻖ اﻷﻛﺜﺮ ﻛﺜﺎﻓﺔ ﰲ اﻟﻜﻮن ﺣﻴﺚ ﻳﻤﻜـﻦ دﻓﻌﻬﺎ إﱃ اﻻﺻﻄ و ﺪام ﻫﺬا أﻣﺮ ﻣﺜـ ﻟﻔﻬـﻢ ﻛﻴﻔﻴﺔ ﻣﻮت اﻟﻨﺠﻮم واﻹﺟﺎﺑـﺔ ﻋـﲆ أﺳـﺌﻠﺔ أﺧﺮى ﻣﺜﻞ ﻣﺎ ﻫﻲ ا ﺼـﺎدر ﻏـ ا ﺘﻮﻗﻌـﺔ اﻟﺘﻲ ﻗﺪ ﺗﺨﻠﻖ ﻣﻮﺟﺎت اﻟﺠﺎذﺑﻴﺔ اﻟﺘﻲ ﻳﻤﻜﻨﻨﺎ اﻛﺘﺸـﺎﻓﻬﺎ ﻋـﲆ اﻷر وﻣ ـﻊ ذﻟــﻚ ض ﻓــﺈن ﻣﺮاﻛﺰﻫـﺎ ﺗﻌـﺞ ﺑـﺎﻟﻨﺠﻮم وﻣﺠﻤﻮﻋـﺔ ﻣـ ﻦ اﻟﺒﻘﺎﻳﺎ اﻟﻨﺠﻤﻴﺔ ﻓﺎﺋﻘﺔ اﻟﻜﺜﺎﻓﺔ ﻣﺜﻞ اﻟﻨﺠﻮم اﻟﻘﺰﻣــﺔ اﻟﺒﻴﻀ ـﺎء واﻟﻨﺠ ـﻮم اﻟﻨﻴﻮﺗﺮوﻧﻴ ـﺔ واﻟﺜﻘﻮب اﻟﺴﻮداء . ﻟﻘﺪ اﺷﺘﺒﻪ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻣﻨﺬ ﻓﱰة ﻃﻮﻳﻠـﺔ ﰲ أن اﻟﻮﺿﻊ ﻣﺜﻞ ﺧﻠﻴﺔ اﻟﻨﺤﻞ ا ﻀﻄﺮﺑﺔ ﻣـﻦ اﻟﻨﺸﺎط ا ﺤﻴﻂ ﺑﺜﻘﺐ أﺳﻮد ﻫﺎﺋﻞ ﻓ ﺴﺘﻜﻮن ﻣﺴﺄﻟﺔ وﻗﺖ ﻓﻘﻂ ﺣﺘﻰ ﻳﺼﻄﺪم ﺟﺴـﻤﺎن ﻧﺠﻤﻴﺎن ﻹﻧﺘﺎج اﻧﻔﺠﺎرات اﺷﻌﺔ ﻏﺎﻣﺎ وﻣـﻊ ذﻟﻚ ﻓﺈن اﻷدﻟﺔ ﻋﲆ ﻫﺬا اﻟﻨﻮع ﻣﻦ اﻻﻧﺪﻣﺎج ﻣﺎ زاﻟﺖ ﺑﻌﻴﺪة ا ﻨﺎل . - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 3 إن