Free Astronomy Magazine January-February 2025 ARABIC VERSION

This passage has blown away most ofthesphericalhaloofgasthatsur- rounds the LMC. Now, for the first time, astronomers havebeenabletomeasurethesize oftheLMC’shalo—somethingthey coulddoonlywithHubble.Inanew studypublishedintheAstrophysical Journal Letters, researchers were surprised to find that it is so ex- tremelysmall—about50,000light- years across. That’s around 10 times smaller than the halos of other galaxies that are the same mass as the LMC. Its compactness tells the storyofitsencounterwiththeMilky Way. “The LMC is a survivor,” said An- drew Fox of AURA/STScI for the Eu- ropeanSpaceAgencyinBaltimore, who was principal investigator on theobservations. “Eventhoughit’s lostalotofitsgas,it’sgotenough left to keep forming new stars. So new star-forming regions can still be created. A smaller galaxy would- n’thavelasted—therewouldbeno gas left, just a collection of aging red stars.” Though quite a bit the worse for wear, the LMC still retains a com- pact, stubby halo of gas — some- thing that it wouldn’t have been able to hold onto gravitationally haditbeenlessmassive.TheLMCis 10 percent the mass of the Milky Way. “Because of the Milky Way’s own gianthalo,theLMC’sgasisgetting truncated,orquenched,” explained STScI’s Sapna Mishra, the lead au- thor of the paper chronicling this discovery. “But even with this cata- strophic interaction with the Milky Way, the LMC is able to retain 10 percent of its halo because of its high mass.” MostoftheLMC’shalowasblown away by a phenomenon called ram- pressure stripping. The dense envi- ronment of the Milky Way pushes back against the incoming LMC and creates a wake of gas trailing the dwarf galaxy — like the tail of a comet. “I like to think of the Milky Way as thisgianthairdryer,andit’sblowing gasofftheLMCasitcomesintous,” said Fox. “The Milky Way is pushing backsoforcefullythattherampres- JANUARY-FEBRUARY2025 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 25 ُﻈﻬﺮ ﻫﺬا اﻟﺮﺳﻢ اﻟﺘﺨ ﻠﻲ ﺳﺤﺎ ﺔ ﻣﺎﺟﻼن اﻟﻜ ى أﺛﻨﺎء ﻣﺮورﻫﺎ ﻋ اﻟﻬﺎﻟﺔ اﻟﻐﺎز ﺔ اﻟﻤﺤ ﻄﺔ ﻤﺠﺮة در اﻟﺘ ﺎﻧﺔ اﻷﻛ ﺣ ﻤ . ﺎً اﻻﺻﻄﺪام إﻟﻰ ﻟﻘﺪ أد ﻧﺴﻒ ﺗﺤـ ﻂ ـﺔ ﻣـﻦ اﻟﻐـﺎز اﻟـ ﻣﻌﻈـﻢ اﻟﻬﺎﻟـﺔ اﻟﻜﺮو ﺴـﺤﺎ ﺔ ﻣـﺎﺟﻼن اﻟﻜـ ى ـﺎر اﻟﻐــﺎز ﻤـﺎ ﺘﻀـﺢ ﻣــﻦ ﺗ ــﺬﻳﻞ اﻟﻤـﺬﻧﺐ وﻣـﻊ ذﻟـﻚﻻ ﺗــﺰال ـﺬﻛﺮﺎ اﻟﻤﺘﺘﺒـﻊ اﻟــﺬ اﻟﻬﺎﻟــﺔ ﻣﻀــﻐﻮﻃﺔ ــﺔ وﻻ ﺘﻮﻗــﻊ اﻟﻌﻠﻤــﺎء أن ﺗﺘﻼﺷــﻰﻫــﺬﻩ اﻟﻬﺎﻟــﺔ اﻟﻤﺘ ﻘ . ﻗـﺎم اﻟﻔﺮ ـﻖ ﻤﺴـﺢ اﻟﻬﺎﻟــﺔ ﺎﺳﺘﺨﺪام ﺿﻮء اﻟ ﻘﺎدم ﻣﻦ اﻟـﺨﻠﻒ ﻟـ 28 ـﻮازار اً ـﺔ ﻣـﻦ اﻟﻨـﻮى اﻟﻤﺠﺮ ـﺔ ا وﻫـﻮ ﻧـﻮع ﺳـﺎﻃﻊ ﻟﻠﻐﺎ ﻟﻨﺸـﻄﺔ ﺗ اﻟـــ ﻠﻤـــﻊ ـــﻮن ﻣﺜـــﻞ ﻋـــ اﻟ اﻟ . ﻤﻨـــﺎرة ﺴـــﻤﺢ ﺿـــﻮءﻫﺎ ﻟﻠﻌﻠﻤـــﺎء ﺑــــ ـــﺔ " " رؤ اﻟﻬﺎﻟـــﺔ اﻟﻤﺘﺪاﺧﻠـــﺔ ﺸـــ ﻞ ﻏـــ ﻣ ﺎﺷــﺮﻣــﻦ ﺧــﻼل اﻣﺘﺼــﺎصﺿــﻮء اﻟــ ـ . ﺨﻠﻔ ﺔ ﺗﻤﺜــﻞ اﻟــ ـ ــﺔ ﺗﻠﺴــ ﻮبﻫﺎﺑــﻞ ﺨﻄﻮط رؤ اﻟﻔﻀــﺎﺋﻲ ﻣــﻦ ﻣــﺪارﻩ ــــــــــــــــــﺪة ﻣـــــــــــــــــﻦ ﺧــــــــــــــــــﻼل ﻏـــــــــــــــــﺎزﺳــــــــــــــــــﺤﺎ ﺔ ﻣـــــــــــــــــﺎﺟﻼن اﻟﻜــــــــــــــــــ ى ـــــــــــــــــﻮازارات اﻟ ﻌ ﺣـــــــــــــــــﻮل اﻷرض إﻟــــــــــــــــــﻰ اﻟ . ] NASA,ESA,R.Crawford(STScI [( ﻟﻘﺪ أدى ﻫﺬا ا ﺮور إﱃ ﻧﺴﻒ ﻣﻌﻈﻢ اﻟﻬﺎﻟـﺔ اﻟﻜﺮوﻳﺔ ﻣـﻦ اﻟﻐـﺎز اﻟﺘـﻲ ﺗﺤـﻴﻂ ﺑﻤﺠـﺮة ﻣﺎﺟﻼن اﻟﻜﱪى . اﻵن وﻟﻠﻤﺮة اﻷوﱃ ﺗﻤﻜﻦ ﻋﻠﻤﺎء اﻟﻔﻠـﻚ ﻣـ ﻦ ﻗﻴﺎس ﺣﺠﻢ ﻫﺎﻟﺔ ﻣﺎﺟﻼن اﻟﻜﱪى وﻫﻮ ﻣـﺎ ﻳﻤﻜﻨﻬﻢ ﻓﻌﻠﻪ ﻓﻘـﻂ ﺑﺎﺳـﺘﺨﺪام ﺗﻠﺴـﻜﻮب ﻫﺎﺑﻞ وﰲ دراﺳﺔ ﺟﺪﻳﺪة ﻧُـ ـ ﴩت ﰲ ﻣﺠﻠـﺔ رﺳﺎﺋﻞ اﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴﺔ ﻓـﻮﺟﺊ اﻟﺒـﺎﺣﺜﻮن ﺑﺎﻛﺘﺸﺎف أﻧﻬﺎ ﺻﻐ ة ﻟﻠﻐﺎﻳﺔ ﺑﻘﻄﺮ ﺣـﻮاﱄ 50000 ﺳﻨﺔ ﺿـﻮﺋﻴﺔ وﻫـﻲ ﺑـﺬﻟﻚ أﺻـﻐﺮ ﺑﺤﻮاﱄ 10 ﻣﺮات ﻣﻦ ﻫﺎﻻت ا ﺠﺮات اﻷﺧﺮى اﻟﺘﻲ ﻟﻬﺎ ﻧﻔﺲ ﻛﺘﻠﺔ ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى وﻳﺤﻜﻲ اﻛﺘﻨﺎزﻫﺎ ﻗﺼﺔ ﻣﻮاﺟﻬﺘﻬـﺎ ﺠـﺮة درب اﻟﺘﺒﺎﻧﺔ . ﻗﺎل أﻧﺪرو ﻓـﻮﻛ ﺲ ﻣـﻦ راﺑﻄـﺔ ﺟﺎﻣﻌـﺎت اﻟﺒﺤﻮث اﻟﻔﻠﻜﻴﺔ و ﻣﻌﻬـﺪ ﻋﻠـﻮم ﺗﻠﺴـﻜﻮب اﻟﻔﻀﺎء ﻟ ﺼﺎﻟﺢ وﻛﺎﻟـﺔ اﻟﻔﻀـﺎء اﻷوروﺑﻴـﺔ ـــ ﰲ ﺑﺎﻟﺘﻴﻤﻮر اﻟﺬي ﻛﺎن ا ﺤﻘـﻖ اﻟﺮﺋﻴـ ﴘﰲ ـ اﻷرﺻﺎد " : ﻣﺎﺟﻼن ا ﻟﻜﱪى ﻫﻲ ﻣﻦ اﻟﻨﺎﺟ وﻋﲆ اﻟﺮ ﻏﻢ ﻣـﻦ أﻧﻬـﺎ ﻓﻘـﺪت اﻟﻜﺜـ ﻣـﻦ ﻏﺎزﻫـﺎ إﻻ أﻧﻬـﺎ ﺣﺼـﻠﺖ ﻋـﲆ ﻣـﺎ ﻳﻜﻔـﻲ ﻮاﺻﻠﺔ ﺗﻜﻮﻳﻦ ﻧﺠﻮم ﺟﺪﻳﺪة وﺑﺎﻟﺘﺎﱄ ﻓـﺈن ﻣﻨﺎﻃﻖ ﺗﺸ ﻜﻞ اﻟﻨﺠﻮم اﻟﺠﺪﻳـﺪة ﻣـﺎ زاﻟـﺖ ﻗﺎﺋﻤﺔ وﻟﻦ ﺗﺴﺘﻤﺮ ﻣﺠﺮة أﺻﻐﺮ ﺣﺠﻤﺎً وﻟﻦ ﻳﺘﺒﻘﻰ ﻓﻴﻬﺎ أي ﻏﺎز ﺑﻞ ﻣﺠﻤﻮ ﻋﺔ ﻣﻦ اﻟﻨﺠﻮم اﻟﺤﻤﺮاء ا ﺘﻘﺎدﻣﺔ ورﻏﻢ أن ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن ا ﻟﻜﱪى أﺻﺒﺤﺖ ﰲ ﺣﺎﻟﺔ أﺳﻮأ ﻛﺜـ اً ﻓﺈﻧﻬـﺎ ﻣﺎ زاﻟﺖ ﺗﺤﺘﻔﻆ ﺑﻬﺎﻟﺔ ﻏﺎزﻳـﺔ ﻣﻀـﻐﻮﻃﺔ ـ وﻫﻮ اﻟ ﴚء اﻟـﺬي ﻟـﻢ ﻳﻜـﻦ ﺑﻮﺳـﻌﻬﺎ أن ﺗﺤﺘﻔ ﻆ ﺑﻪ ﺟﺎذﺑﻴﺎً ﻟﻮ ﻛﺎﻧﺖ أﻗﻞ ﻛﺘﻠﺔ . ﺗﺒﻠﻎ ﻛﺘﻠﺔ ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى 10 % ﻣﻦ ﻛﺘﻠﺔ ﻣﺠﺮة درب اﻟﺘﺒﺎﻧﺔ . ـ ﴍﺣﺖ ﺳﺎﺑﻨﺎ ﻣﻴـ ﴩا ﻣـﻦ ﻣﻌﻬـﺪ ﻋﻠـﻮم ﺗﻠﺴﻜ ﻮب اﻟﻔﻀﺎء، وا ﺆﻟﻔﺔ اﻟﺮﺋﻴﺴﻴﺔ ﻟﻠﻮرﻗﺔ اﻟﺒﺤﺜﻴﺔ اﻟﺘﻲ ﺗﻮﺛﻖ ﻫﺬا اﻻﻛﺘﺸﺎف " : ﺑﺴـﺒﺐ اﻟﻬﺎﻟﺔ اﻟﻌﻤﻼﻗﺔ ﺠﺮة درب اﻟﺘﺒﺎﻧﺔ، ﻓﺈن ﻏﺎز ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى ﻳﺘﻀﺎءل أو ﻳﻨﻄﻔﺊ . وﻟﻜﻦ ﺣﺘﻰ ﻣﻊ ﻫﺬا اﻟﺘﻔﺎﻋﻞ ا ﻟﻜـﺎرﺛﻲ ﻣـﻊ ﻣﺠﺮة درب اﻟﺘﺒﺎﻧﺔ ﻓـﺈن ﺳـﺤﺎﺑﺔ ﻣـﺎﺟﻼن اﻟﻜﱪى ﻗﺎدرة ﻋﲆ اﻻﺣﺘﻔـﺎظ ﺑﻨﺤـﻮ 10 % ﻣﻦ ﻫﺎﻟﺘﻬﺎ ﺑﺴﺒﺐ ﻛﺘﻠﺘﻬﺎ اﻟﻌﺎﻟﻴﺔ ." ﻟﻘﺪ ﺗﻢ ﻧﺴﻒ ﻣﻌﻈﻢ ﻫﺎﻟﺔ ﺳﺤﺎﺑﺔ ﻣـﺎﺟﻼن اﻟﻜﱪ ى ﺑﻮاﺳـﻄﺔ ﻇـﺎﻫﺮة ﺗﺴـﻤﻰ ﺗﺠﺮﻳـﺪ اﻟﻀﻐﻂ ﺣﻴﺚ ﺗﻌﻤﻞ اﻟﺒﻴﺌﺔ اﻟﻜﺜﻴﻔـﺔ ﺠـﺮة درب اﻟﺘﺒﺎﻧـﺔ ﻋـﲆ دﻓـﻊ ﺳـﺤﺎﺑﺔ ﻣـﺎﺟﻼن اﻟﻜﱪى اﻟ ﻘﺎدﻣﺔ إﱃ اﻟﺨﻠﻒ وﺗﻜﻮﻳﻦ أﺛﺎر ﻣﻦ اﻟﻐﺎز ﺗﺘﺒﻊ ا ﺠﺮة اﻟﻘﺰﻣﺔ اﻟﺘﻲ ﺗﺸﺒﻪ ل ﻮ ذﻳـ ا ﺬﻧﺒ . ﺎت ﻗﺎل ﻓﻮﻛﺲ ": أﺣﺐ أن أﺗﺨﻴـﻞ درب اﻟﺘﺒﺎﻧـﺔ ﻋﲆ أﻧﻬﺎ ﻣﺠﻔﻒ ﺷﻌﺮ ﻋﻤﻼق وﻫـﻮ ﻳـﻨﻔﺦ اﻟﻐﺎز ﺑﻌﻴﺪ اً ﻋﻦ ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى - ﻳﻨﺎﻳﺮ ﻓﺒﺮﺍﻳﺮ 2 0 2 5