Free Astronomy Magazine July-August 2024 ARABIC VERSION

billion years in the past, when the Universe was only a quarter of its current age, using a feature of the large-scale structure of the Universe called Baryon Acoustic Oscillations (BAO). BAO are the leftover imprint of pressure waves that permeated the early Universe when it was nothing but a hot, dense soup of subatomic particles. As the Universe expanded and cooled the waves stagnated, freezing the ripples in place and seeding future galaxies in the dense areas. This pattern, re- sembling the rippling surface of a pond after a handful of pebbles is tossed in, can be seen in DESI’s de- tailed map, which shows strands of galaxies clustered together, sepa- rated by voids where there are fewer objects. At a certain distance, the BAO pattern becomes too faint to detect using typical galaxies. So instead astronomers look at the ‘shadow’ of the pattern as it’s back- lit by extremely distant, bright ga- lactic cores known as quasars. As the quasars’ light travels across the cosmos it gets absorbed by inter- galactic clouds of gas, allowing as- tronomers to map the pockets of dense matter. To implement this technique, researchers used 450,000 quasars — the largest set ever col- lected for this type of study. With DESI’s unique ability to map millions of objects both near and far, the BAO pattern can be used as a cosmic ruler. By mapping nearby galaxies and distant quasars, as- tronomers can measure the spread of the ripples across several periods of cosmic history to see how dark energy has stretched the scale over time. “We’re incredibly proud of the data, which have produced world-leading cosmology results,” said Michael Levi, DESI director and LBNL scientist. “So far we’re seeing basic agreement with our best model of the Universe, but we’re also seeing some potentially inter- esting differences that could indi- cate dark energy is evolving with time.” ﺷـــــﺮ ﺤﺔ ـ ﻣـــــﻦ اﻟـــــ ﺗـــــﻢ ﻤﻌﻬـــــﺎ ﻓـــــﻲ اﻟﺴـــــﻨﺔ اﻷوﻟـــــﻰﻣـــــﻦ ﻣﺴـــــﺢ ـــــﺔ اﻷ ﻌـــــﺎد ﻟﻠﻤﺠـــــﺮات اﻟـــــ ﺨﺮﻄﺔ ﺛﻼﺛ أداة اﻟ ﺘﺤﻠﻴــــــــــــﻞ اﻟﻄ ﻔــــــــــــﻲ ﻟ ﻠﻄﺎﻗــــــــــــﺔ اﻟﻤﻈﻠﻤــــــــــــﺔ ) DESI ( ﺗﺤـــــــــــــﺪد ﻣــــــــــــﻊ اﻟﺘﻌﻠ ﻘــــــــــــﺎت اﻟﺘﻮﺿــــــــــــﻴﺤ ﺔ اﻟــــــــــــ اﻟﻤـــــ ات اﻟﺮ ﺴـــــ ﺔ ﻓـــــﻲ اﻟـــــ ـ ﺨﺮﻄﺔ وﺗﻮﺟـــــﺪ اﻷرضﻋﻨـــــﺪ اﻟـــــ ـ ـــــﺚ ﺗـــــﻢ رﺳـــــﻢ أ ﻌـــــﺪ اﻟﻤﺠـــــﺮات ﻋﻠـــــﻰ ﺤﺎﻓﺔ ﺣ ﻣﺴـــــﺎﻓﺎت ﺗ ﻠــــــﻎ 11 ـــــﺎرﺳــــــﻨﺔ ﺿـــــﻮﺋ ﺔ ﻣﻠ و ــــــﻞ ﻧﻘﻄـــــﺔ ﺗﻤﺜــــــﻞ ﻣﺠـــــﺮة . واﺣــــــﺪة ﺘﻀـــــﻤﻦ ﻫــــــﺬا اﻹﺻـــــﺪار ﻣــــــﻦ ﺧﺮﻄﺔ أداة ) DESI ( 600,000 ﻣﺠﺮة، أي أﻗﻞ ﻣﻦ 0.1 ـ ﻣﻦ اﻟ % ﺤ ﻢ اﻟ ﺎﻣﻞ ﻟﻠﻤﺴﺢ . رﺑﻊ ﻋﻤﺮه اﻟﺤﺎﱄ ﻓﻘ ﻂ وذﻟﻚ ﺑﺎﺳﺘﺨﺪام ﺳﻤﺔ ﻣﻦ ﺳﻤﺎت اﻟﺒﻨﻴـﺔ واﺳـﻌﺔ اﻟﻨﻄـﺎق ﻟﻠﻜـﻮن ﺗﺴﻤﻰ ﺗﺬﺑﺬﺑﺎت ﺑـﺎرﻳﻮن اﻟﺼـﻮﺗﻴﺔ ) BAO .( ﺗﺬﺑـﺬﺑﺎت ﺑـﺎرﻳﻮن اﻟﺼـﻮﺗﻴﺔ ﻫـﻲ اﻟﺒﺼـﻤﺔ ا ﺘﺒﻘﻴﺔ ﻮﺟـﺎت اﻟﻀـﻐﻂ اﻟﺘـﻲ ﺗﻐﻠﻐﻠـﺖ ﰲ اﻟﻜﻮن ا ﺒﻜﺮ ﻋﻨﺪﻣﺎ ﻟﻢ ﻳﻜﻦ ﺳﻮى ﻣـﺎ ﻳﺸـﺒﻪ اﻟ اﻟ ﺤﺴﺎء اﻟ ﺴﺎﺧﻦ و ﻜﺜﻴـﻒ ﻣـﻦ اﻟﺠﺴـﻴﻤﺎت دون اﻟﺬرﻳﺔ ﻣﻊ ﺗﻮﺳﻊ اﻟﻜﻮن وﺗﱪﻳﺪه رﻛﺪت ا ﻮﺟـﺎت ﻣﻤـﺎ أدى إﱃ ﺗﺠﻤﻴـﺪ اﻟﺘﻤﻮﺟـﺎت ﰲ ﻣﻜﺎﻧﻬﺎ وﺑﺬر ا ﺠﺮات ا ﺴﺘﻘﺒﻠﻴﺔ ﰲ ا ﻨـﺎﻃﻖ اﻟﻜﺜﻴﻔﺔ . ﻳﻤﻜﻦ رؤﻳﺔ ﻫﺬا اﻟﻨﻤﻂ اﻟﺬي ﻳﺸـﺒﻪ اﻟﺴﻄﺢ ا ﺘ ﻤﻮج اﻟﺬي ﻳﻈﻬﺮ ﺑﻌﺪ رﻣﻲ ﺣﻔﻨـﺔ ﻣﻦ اﻟﺤﴡ اﻟﰲ ﰲ ﺑﺮﻛﺔ ﺨﺮﻳﻄﺔ اﻟﺘﻔﺼـﻴﻠﻴﻠﺔ ) ﻷداة DESI ( واﻟﺘ ـﻲ ﺗُﻈﻬــ ﺮ ﺧﻴﻮﻃــﺎً ﻣــﻦ ا ﺠﺮات ﻣﺘﺠﻤﻌ ﺔ ﻣﻌـﺎً ﻣﻔﺼـﻮﻟﺔ ﺑﻔﺮاﻏـﺎت ﺣﻴﺚ ﻳﻮﺟﺪ ﻋﺪد أﻗﻞ ﻣﻦ اﻷﺟﺴﺎم . ﻋﲆ ﻣﺴﺎﻓﺔ ﻣﻌﻴﻨـﺔ ﻳﺼـﺒﺢ ﻧﻤـﻂ ﺗﺬﺑـﺬﺑﺎت ﺑﺎرﻳﻮن اﻟﺼﻮﺗﻴﺔ اُ ﺟﺪ ﺎُ ﺧﺎﻓﺘ ﺑﺤﻴﺚ ﻻ ﻳﻤﻜـﻦ اﻛﺘ ﺸﺎﻓﻪ ﺑﺎﺳﺘﺨﺪام ا ﺠﺮات اﻟﻨﻤﻮذﺟﻴـﺔ ﻟـﺬا اﻟﻨﻤﻮذج، ﺣﻴـﺚ ﺗـﺘﻢ إﺿـﺎءﺗﻪ ﻣـﻦ اﻟﺨﻠـﻒ ﺑﻮاﺳﻄﺔ ﻧﻮى ﻣﺠﺮﻳﺔ ﺑﻌﻴﺪة ﻟﻠﻐﺎﻳﺔ وﻣﴩـﻗﺔ ﺑﺪﻻً ﻣﻦ ذﻟﻚ ﻳﻨﻈﺮ ﻋﻠﻤـﺎء اﻟ " ﻇـﻞ " ﻔﻠـﻚ إﱃ اﻟﻨﻤـﻮذج ﺣﻴـﺚ ﺗـﺘﻢ إﺿـﺎءﺗﻪ ﻣـﻦ اﻟﺨﻠـﻒ ﺑﻮاﺳﻄﺔ ﻧﻮى ﻣﺠﺮﻳﺔ ﺑﻌﻴﺪة ﻟﻠﻐﺎﻳﺔ وﻣ ﴩﻗﺔ ـ ﺗُﻌﺮف ﺑﺎﺳﻢ اﻟﻜﻮازارات . أﺛﻨﺎء ﺳﻔﺮ ﺿﻮء اﻟﻜﻮازارات ﻋﱪ اﻟﻜﻮن ﻳـﺘﻢ اﻣﺘﺼﺎ ﺻﻪ ﺑﻮاﺳﻄﺔ ﺳﺤﺐ اﻟﻐﺎز ﺑ ا ﺠﺮات ﻣﻤﺎ ﻳﺴﻤﺢ ﻟﻌﻠﻤـﺎء اﻟﻔﻠـﻚ ﺑﺮ ﺳـﻢ ﺧﺮﻳﻄـﺔ ﻟﺠﻴﻮب ا ﺎدة اﻟﻜﺜﻴﻔﺔ . ﻟﺘﻨﻔﻴﺬ ﻫـﺬه اﻟﺘﻘﻨﻴـﺔ اﺳﺘﺨﺪم اﻟﺒﺎﺣﺜﻮن 450 أﻟـﻒ ﻛـﻮازار وﻫـﻲ أﻛﱪ ﻣﺠﻤﻮﻋﺔ ﺗﻢ ﺟﻤﻌﻬﺎ ﻋﲆ اﻹﻃـﻼق ﻟﻬـﺬا اﻟﻨﻮع ﻣﻦ اﻟﺪراﺳﺎت . ﺑﻔﻀﻞ ﻗﺪرة أداة DESI اﻟﻔﺮﻳـﺪة ﻋـﲆ رﺳـﻢ ﺧﺮﻳﻄﺔ ﻼﻳ اﻟﻜﺎﺋﻨـﺎت اﻟﻘﺮﻳﺒـﺔ واﻟﺒﻌﻴـﺪة ﻳﻤﻜـﻦ اﺳـﺘﺨﺪام ﻧﻤـﻂ ﺗﺬﺑــﺬﺑﺎت ﺑــﺎرﻳﻮن اﻟﺼﺔﺗﻲ ﺧﺮاﺋﻂ ﻟﻠﻤﺠﺮات اﻟﻘﺮﻳﺒﺔ ــــ اﻟﺼﻮﺗﻴﺔ ﻛﻤﺴﻄﺮة ﻛﻮﻧﻴﺔ وﻣﻦ ﺧـﻼل رﺳـﻢ ﺧﺮاﺋﻂ ﻟﻠﻤﺠﺮات اﻟﻘﺮﻳﺒﺔ واﻟﻜﻮازارات اﻟﺒﻌﻴﺪة ﻳﻤﻜﻦ ﻟﻌﻠﻤﺎء اﻟﻔﻠﻚ اﻟﻘﻴـﺎم ﺑ ﻘﻴـﺎس اﻧﺘﺸـﺎر اﻟﺘﻤﻮﺟﺎت ﻋـﱪ ﻋـﺪة ﻓـﱰات ﻣـﻦ اﻟﺘـﺎرﻳﺦ اﻟﻜﻮﻧﻲ ﻌﺮﻓﺔ ﻛﻴﻒ وﺳّﻌﺖ اﻟ ﻄﺎﻗﺔ ا ﻈ ﻠﻤـﺔ ا ﻘﻴﺎس ﺑﻤﺮور اﻟﻮﻗ . ﺖ ﻗﺎل ﻣﺎﻳﻜﻞ ﻟﻴﻔﻲ ﻣﺪﻳﺮ ﻣﻌﻬﺪ (DESI) وﻋﺎﻟﻢ ﺑ ﻤﺨﺘـﱪ ﻟـﻮرﻧﺲ ﺑـ ﻛﲇ اﻟــﻮﻃﻨﻲ " : ﻧﺤـﻦ ﻓﺨﻮرون ﻟﻠﻐﺎﻳﺔ ﺑﺎﻟﺒﻴﺎﻧﺎت اﻟﺘﻲ أﻇﻬﺮت ﻧﺘﺎﺋﺞ راﺋﺪة ﰲ ﻋﻠﻢ اﻟﻜﻮﻧﻴﺎت ﻋﲆ ﻣﺴﺘﻮى اﻟﻌﺎﻟﻢ ." " ﺣﺘﻰ اﻵن ﻧﺮى اﺗﻔﺎﻗًﺎً ﻣﻊ أﻓﻀﻞ ﻧﻤﻮذج ﻟﺪﻳﻨﺎ ﻟﻠﻜﻮن ﻟﻜﻨﻨﺎ ﻧﺮى أﻳ ﺎ ﺑﻀـ ﻌـﺾ اﻻﺧﺘﻼﻓـ ﺎت ا ﺜ ة ﻟﻼﻫﺘﻤﺎم اﻟﺘﻲ ﻳﻤﻜـﻦ أن ﺗﺸـ إﱃ أن اﻟﻄﺎﻗﺔ ا ﻈﻠﻤﺔ ﻗﺪ ﺗﺘﻄﻮر ﻣﻊ ﻣﺮور اﻟﻮﻗﺖ ". - ﻳﻮﻟﻴﻮ ﺃﻏﺴﻄﺲ 2 0 2 4