Free Astronomy Magazine September-October 2025 ARABIC VERSION

SEPTEMBER-OCTOBER2025 called Monte Carlo simulations stretchingto10billionyearsintothe future. “Because there are so many vari- ables that each have their errors, thataccumulatestoratherlargeun- certainty about the outcome, lead- ing to the conclusion that thechance of a direct collision is only 50% within the next 10 billion years,” said Sawala. “The Milky Way and Andromeda alonewouldremaininthesame plane as they orbit each other, but this doesn’t mean they need to crash. They could still go past each other,” Sawala added. Researchersalsoconsideredtheef- fects of the orbits of Andromeda’s large satellite galaxy, M33, and a satellite galaxy of the Milky Way called the Large Magellanic Cloud (LMC). “The extra mass of Andromeda’s satellite galaxy M33 pulls the Milky Way a little bit more towards it. However, we also show that theLMC pulls the Milky Way off the or- bital plane and away from Androm- eda. It doesn’t mean that the LMC will save us from that merger, butit makes it a bit less likely,” said Sawala. In about half of the simulations, the two main galaxies fly past each oth- er separated by around half a mil- lionlight-yearsorless(fivetimesthe Milky Way’s diameter). They move outward but then come back and eventually merge in the far future. The gradual decay of the orbit is causedbyaprocesscalleddynamical frictionbetweenthevastdark-mat- terhalosthatsurroundeachgalaxy at the beginning. Inmostoftheothercases,thegalax- ies don’t even come close enoughfor dynamical friction to work effec- tively. In this case, the two galaxies can continue their orbital waltz fora very long time. The new result also still leaves a small chance of around 2%for a head-on collision between the gal- axies in only 4 to 5 billion years. Considering that the warming Sun makes Earth uninhabitable in roughly1billionyears,andtheSun itselfwilllikelyburnoutin5billion years,acollisionwithAndromedais theleastofourcosmicworries.   ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 52 ﻗﺎل ﺳﺎواﻻ ": ﻷن ﻫﻨﺎك اﻟﻌﺪﻳﺪ ﻣﻦ ا ﺘﻐـ ات اﻟﺘﻲ ﻟﻜﻞ ﻣﻨﻬﺎ أﺧﻄﺎؤﻫﺎ واﻟﺘﻲ ﺗ ﺮاﻛﻢ إﱃ ﺣـﺪ ﻛﺒ ﻋﺪم اﻟﻴﻘ ﺑﺸﺄن اﻟﻨﺘﻴﺠﺔ ﻣﻤﺎ ﻳﺆدي إﱃ اﺳﺘﻨﺘﺎج أن ﻓﺮﺻﺔ اﻻﺻـﻄﺪام ا ﺒـﺎﴍ ﻫـﻲ 50 ٪ ﻓﻘﻂ ﺧـ ـ ﻼل اﻟﻌـ ﴩة ﻣﻠﻴـﺎرات ﺳـﻨﺔ اﻟ و ﻘﺎدﻣﺔ ﺳﺘﺒﻘﻰ ﻣﺠﺮﺗﺎ درب اﻟﺘﺒﺎﻧﺔ وﻣﺠﺮة ا ﺮأة ا ﺴﻠﺴﻠﺔ ) أﻧﺪروﻣﻴﺪا ( وﺣﺪﻫﻤﺎ ﰲ ﻧﻔﺲ ا ﺴﺘﻮى أﺛﻨﺎء دوراﻧﻬﻤﺎ ﺣﻮل ﺑﻌﻀﻬﻤﺎ ﻟﻜـﻦ ﻫﺬا ﻻ ﻳﻌﻨﻲ أﻧﻬﻤـﺎ ﺑﺤﺎﺟـﺔ إﱃ اﻻﺻـﻄﺪام ﻻ ﻳﺰال ﻣﻦ ا ﻤ ﻜﻦ أن ﺗﻤـﺮا ﺑﺠﺎﻧـﺐ ﺑﻌﻀـﻬﻤﺎ . ادرس اﻟﺒﺎﺣﺜﻮن أﻳﻀًﺎ آﺛـﺎر ﻣـﺪارات ﻣﺠـﺮة أﻧﺪروﻣﻴـﺪا اﻟﺘﺎﺑﻌـﺔ اﻟﻜﺒـ ة ، M33 ، وﻣﺠـﺮة درس اﻟﺒﺎﺣﺜﻮن أﻳﻀ ﺎً آﺛـﺎر ﻣـﺪارات اﻟﺘﺎﺑﻌـﺔ اﻟﻜﺒــ ة )M33 ( ﺠــﺮة ا ــﺮأة ا ﺴﻠﺴــﻠﺔ ) أﻧﺪروﻣﻴﺪا ( وﻣﺠﺮة ﺗﺎﺑﻌﺔ ﺠﺮة درب اﻟﺘﺒﺎﻧـﺔ ﺗﺴﻤﻰ ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى ﺗﺴﺤﺐ اﻟﻜﺘﻠﺔ اﻹﺿﺎﻓﻴﺔ ﺠﺮة أﻧﺪروﻣﻴـﺪا اﻟﺘﺎﺑﻌـﺔ (M33) درب اﻟﺘ ﺒﺎﻧﺔ ﻧﺤﻮﻫﺎ أﻛﺜﺮ ﻗﻠﻴﻼً وﻣﻊ ذﻟﻚ ﻓﻘـﺪ أ ﺎً ﻇﻬﺮﻧﺎ أﻳﻀـ أن ﺳـﺤﺎﺑﺔ ﻣـﺎﺟﻼن اﻟﻜـﱪى ﺗﺴﺤﺐ ﻣﺠﺮة درب اﻟﺘﺒﺎﻧﺔ ﺑﻌﻴﺪ اً ﻋﻦ ا ﺴﺘﻮى ا ﺪاري وﺑﻌﻴﺪ اً ﻋـﻦ ﻣﺠـﺮة ا ـﺮأة ا ﺴﻠﺴـﻠﺔ ) أﻧﺪروﻣﻴﺪا ( . ﻗﺎل ﺳﻮاﻻ " : ﻫﺬا ﻻ ﻳﻌﻨﻲ أن ﺳﺤﺎﺑﺔ ﻣﺎﺟﻼن اﻟﻜﱪى ﺳﺘﻨﻘﺬﻧﺎ ﻣـﻦ ﻫـﺬا اﻻﻧـﺪﻣ ﺎج وﻟﻜﻨـﻪ ﻳﻘﻠﻞ ﻣﻦ اﺣﺘﻤﺎﻟﻴﺔ ﺣﺪوﺛ ".ﻪ ﺗﻈﻬـﺮ ﺣـﻮاﱄ ﻧﺼـﻒ ﻋﻤﻠﻴـﺎت ا ﺤﺎﻛـﺎة أن ا ﺠﺮﺗﺎ ن اﻟﺮﺋﻴﺴﻴﺘﺎن ﺗﻤﺮان ﺑﺠﺎﻧﺐ ﺑﻌﻀﻬﻤﺎ وﻳﻔﺼﻞ ﺑﻴﻨﻬﻤﺎ ﺣﻮاﱄ ﻧﺼـﻒ ﻣﻠﻴـﻮن ﺳـﻨﺔ ﺧﻤﺴﺔ ) ﺿﻮﺋﻴﺔ أو أﻗﻞ أﺿـﻌﺎف ﻗﻄـﺮ درب اﻟﺘﺒﺎﻧﺔ .( ﺗﺘﺤﺮﻛﺎن ﻧﺤﻮ اﻟﺨﺎرج ﺛـﻢ ﺗﻌـﻮدان وﺗﻨـﺪﻣﺠﺎن ﰲ اﻟﻨﻬﺎﻳـﺔ ﰲ ا ﺴـﺘﻘﺒﻞ اﻟﺒﻌﻴـﺪ . ﻳﺤﺪث اﻻﻧﻜﻤﺎش اﻟﺘـﺪرﻳﺠﻲ ﻟﻠﻤـﺪار ﻧﺘﻴﺠـﺔ ﻋﻤﻠﻴـﺔ ﺗ ﺴـﻤﻰ اﻻﺣﺘﻜـﺎك اﻟـﺪﻳﻨﺎﻣﻴﻜﻲ ﺑـ ﻫﺎﻻت ا ﺎدة ا ﻈﻠﻤﺔ اﻟﺸﺎﺳﻌﺔ اﻟﺘـﻲ ﺗﺤـﻴﻂ ﺑﻜﻞ ﻣﺠﺮة ﰲ اﻟﺒﺪاﻳﺔ . ﰲ ﻣﻌﻈﻢ اﻟﺤﺎﻻت اﻷﺧﺮى ﻻ ﺗﻘﱰب ا ﺠـﺮات ﺑﻤـﺎ ﻳﻜﻔـﻲ ﻟﻴﻌﻤـﻞ اﻻﺣﺘﻜـﺎك اﻟـ ﺪﻳﻨ ﺎﻣﻴﻜﻲ ﺑﻔﻌﺎﻟﻴﺔ . ﰲ ﻫـﺬه اﻟﺤﺎﻟـﺔ ﻳﻤﻜـﻦ ﻟﻠﻤﺠـﺮﺗ ﻣﻮاﺻﻠﺔ ﺣﺮﻛﺘﻬﻤﺎ ا ﺪارﻳﺔ ﻟﻔﱰة ﻃﻮﻳﻠﺔ ﺟﺪًا . ﻛﻤﺎ أن اﻟﻨﺘﻴﺠﺔ اﻟﺠﺪﻳﺪة ﻻ ﺗﺰال ﺗﱰك ﻓﺮﺻـﺔ ﺿـﺌﻴﻠﺔ ﺗﺒﻠـﻎ ﺣـﻮاﱄ 2 % ﻟﺤـﺪوث ﺗﺼـﺎدم ﻣﺒــﺎﴍ ﺑــ ا ﺠــﺮﺗ ﰲ ﻏﻀــﻮن 4 إﱃ 5 ﻣﻠﻴﺎرات ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﻓﻘﻂ . ﺑﺎﻟﻨﻈﺮ إﱃ أن ارﺗﻔﺎع درﺟﺔ ﺣـﺮارة اﻟﺸـﻤﺲ ﻳ ﺠﻌﻞ اﻷرض ﻏ ﺻﺎﻟﺤﺔ ﻟ ﻠﺤﻴﺎة ﺑﻌﺪ ﺣـﻮاﱄ ﻣﻠﻴﺎر ﻋﺎم، وﻣﻦ ا ﺮﺟﺢ أن ﺗﺤﱰق اﻟﺸـﻤﺲ ﻧﻔﺴﻬﺎ ﺑﻌﺪ 5 ﻣﻠﻴﺎرات ﻋﺎم ﻓـﺈن اﻻﺻـﻄﺪام ﺑﻤﺠﺮة ا ﺮأة ا ﺴﻠﺴﻠﺔ ) أﻧﺪروﻣﻴﺪا ( ﻫـﻮ أﻗـﻞ ا ﺨﺎوف اﻟﻜﻮﻧﻴﺔ إﺛﺎرة ﻟﻠﻘﻠﻖ . ﺗﻤﻸ ﻣﺠﺮة اﻟﻤـﺮأة اﻟﻤﺴﻠﺴـﻠﺔ ا) ـﺪا ﻧﺪروﻣ ﺠـﺎل ﻣ ( ـــﺔ اﻟﺮؤ . ـــﺪأت ﻣﺠـــﺮة در اﻟﺘ ﺎﻧـــﺔ ﺗﻈﻬـــﺮ ﺗﺸـــﻮﻫﺎت ـ ﺴـ ﺐ ﻗــﻮة اﻟـ ــﺔ ﻣـﻦ ﻣﺠــﺮة ﺠﺬب اﻟﻤﺪ ا) ــﺪا ﻧﺪروﻣ ( ﻫــــــﺬا ﻣﺠـــــــﺮد ﺳــــــ ﻨﺎر ﻮ واﺣـــــــﺪ ﻣــــــﻦ اﻟﺴـــــــ ﻨﺎر ﻮﻫﺎت ـــﺎراتﺳـــﻨﺔ اﻟﻘﺎدﻣـــﺔ اﻟﻤﺘﻮﻗﻌـــﺔ ﺧـــﻼل اﻟﻌﺸـــﺮة ﻣﻠ ﻗﺪ ﻻ ﺗﺼﻄﺪم ﻣﺠﺮة در اﻟﺘ ﺎﻧﺔ ﺑـ M31 إﻃﻼﻗﺎً . [ScienceIllustration: NASA, ESA, Z. Levay andR. van der Marel (STScI), T. Hallas,and A. Mellinger] ﺳﺒﺘﻤﺒﺮ - ﺃﻛﺘﻮﺑﺮ 2 0 2 5