Free Astronomy Magazine March-April 2024 ARABIC VERSION

A 34 Gemini South captures the aftermath of past merger by NOIRLab − Josie Fenske n astounding number of galaxies populate the ob- servable Universe, with re- cent estimates placing that number anywhere from 100 billion to 2 tril- lion. And, akin to snowflakes, no two are exactly alike. But depending on their visual appearance and phys- ical features they can be divided into four broad classes: elliptical, lenticu- lar, irregular and spiral, with many subclasses in between. However, galaxies are dynamic objects that evolve over time as they interact with their surrounding environ- ment, meaning that an individual galaxy may fall under multiple clas- sifications throughout its lifetime. Such is thought to be the case with NGC 4753, which astronomers hy- pothesize began as a normal lentic- ular galaxy but morphed into the more specific peculiar class after a merger with a nearby dwarf galaxy over a billion years ago. Discovered by astronomer William Herschel in 1784, NGC 4753 displays some truly fascinating features. In this image captured by the Gemini South telescope, one half of the In- ternational Gemini Observatory op- erated by NSF’s NOIRLab, the galaxy’s intricate dust lanes are a sight to behold. NGC 4753 is located about 60 million light-years away in the constellation Virgo. It is a mem- ber of the NGC 4753 Group of gal- axies within the Virgo II Cloud — a series of at least 100 galaxy clusters and individual galaxies stretching off the southern edge of the Virgo Supercluster. NGC 4753’s distinct dust lanes, ap- pearing to twist and turn around the galaxy’s nucleus, have long in- trigued astronomers, and are the ir- regular features that give it its ‘peculiar’ classification. Seen nearly edge-on from Earth, this galaxy can appear rather mystifying. But in 1992 a team of astronomers led by Tom Steiman-Cameron, now a sen- ior research scientist at Indiana Uni- versity, published a detailed study of NGC 4753 in which they found that its complicated shape is likely the re- sult of a merger with a small com- panion galaxy. “ Galaxies that gobble up another galaxy often look like train wrecks, – said Steiman-Cameron − and this is a train-wreck galaxy.” Galaxy mergers occur when two (or more) galaxies collide, causing their material to mix and significantly al- tering the shape and behavior of each galaxy involved. In the case of NGC 4753, it is thought that the once standard lenticular galaxy merged with a nearby gas-rich dwarf galaxy about 1.3 billion years ago. The gas of the dwarf galaxy, coupled with bursts of star forma- tion triggered by this galactic colli- sion, injected the system with vast amounts of dust. The galaxy’s in- ward spiral due to gravity then caused the accumulated dust to MARCH-APRIL 2024 " ﺳﺎوث ﺟ ﻤ " ﻘﻂﺘﻠ آﺛﺎراﻧﺪﻣﺎج ﻣﺠﺮيﻗﺪ ﻢ : ﻘﻠﻢ ﺟﻮزيﻓ ﻨﺴﻜﻲ - ﻣﺨﺘ ﻧﻮﻳﺮﻻب ﻳﺤـﺪث اﻧــﺪﻣﺎج اﻟﻤﺠــﺮات ﻋﻨــﺪﻣﺎ ﺗﺼــﻄﺪم ﻣﺠﺮ ـﺎن أو ) أﻛـ ( إﻟــﻰ اﻣـ اج اﻟﻤــﻮاد اﻟـ ، ﻣﻤــﺎ ﻳـﺆد ـ ﺨﺎﺻﺔ ﺑﻬـﺎ وﺗﻐﻴ ﺷ ﻞ وﺳﻠﻮك ﻞ ﻣﺠﺮة ـﺔ ﺸـ ﻞ ﻛﺒـ ﻣﻌﻨ . ﻓﻲﺣﺎﻟﺔ NGC 4753 ُﻌﺘﻘﺪ أن اﻟﻤﺠـﺮة اﻟﻌﺪﺳـ ﺔ اﻟﻘ ﺎﺳــــ ﺔ اﻧـــــﺪﻣﺠﺖ ﻣـــــﻊ ﻣﺠــــﺮة ـــــﺔ ـــــﺔ ﻏﻨ ﻗﺰﻣـــــﺔ ﻗﺮ ﺎﻟﻐﺎزﻣﻨﺬ ﺣﻮاﻟﻲ 1.3 ﻣﻠ ﺎرﺳﻨﺔ . إن ﻏــﺎز اﻟﻤﺠـــﺮة اﻟﻘﺰﻣــﺔ، ﻣﻘﺮوﻧـــﺎ ﺎﻧــﺪﻓﺎﻋﺎت ﺗﺸـــ ﻞ اﻟﻨﺠـــﻮم اﻟﻨﺎ ﻤـــﺔ ﻋـــﻦ ﻫـــﺬا اﻻﺻـــﻄﺪام اﻟﻤﺠـــﺮي ﻗـــﺪ ﺣﻘـــ ـــﺎر ـــﺎتﻫﺎﺋﻠـــﺔ ﻣـــﻦ اﻟﻐ ﻦ اﻟﻨﻈـــﺎم ﺑ ﻤ وﻗـــﺪ أد دوران اﻟﻤﺠـــــﺮة ﻧﺤـــــﻮ اﻟـــــﺪاﺧﻞ ﺴـــــ ﺐ ـ اﻟـــــ ﺠﺎذﺑ ﺔ إﻟـــــﻰ ﻇﻬﻮراﻟﻐ ﺎر اﻟﻤ ا ﻢ ﻋﻠﻰﺷ ﻞ ﻗﺮص ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 34 ﻫﻨـﺎك ﻋﺪد ﻣﺬﻫﻞ ﻣﻦ ا ﺠﺮات ﻳﺴﻜﻦ اﻟﻜﻮن ا ﺮﺋﻲ ﻣﻊ ﺗﻘﺪﻳﺮات ﺣﺪﻳﺜﺔ ﺗﻀﻊ ﻫﺬا اﻟﻌﺪد ﰲ أي ﻣﻜﺎن ﻣﻦ 100 ﻣﻠﻴﺎر إﱃ 2 ﺗﺮﻳﻠﻴﻮن وﻛﻤـﺎ ﻫﻮ اﻟﺤﺎل ﻣﻊ رﻗﺎﻗﺎت اﻟﺜ ﻠﺞ، ﻻ ﻳﻮﺟـﺪ اﺛﻨـﺎن ﻣﺘﺸـﺎﺑﻬ ﺘ ﺎن ﺗﻤﺎﻣـ ﺎً وﻟﻜ ـﻦ اﻋﺘﻤﺎد اً ﻋﲆ ﻣﻈﻬﺮﻫﺎ اﻟﺒ ـ ﴫي وﺧﺼﺎﺋﺼﻬﺎ اﻟﻔﻴﺰﻳﺎﺋﻴﺔ ﻳﻤﻜﻦ ﺗﻘﺴـﻴﻤﻬﺎ إﱃ أرﺑـﻊ ﻓﺌـﺎ ت : ﻋﺮﻳﻀﺔ ﺑﻴﻀـﺎوﻳﺔ اﻟﺸـﻜﻞ وﻋﺪﺳـﻴﺔ وﻏـ ﻣﻨﺘﻈﻤﺔ وﺣﻠﺰوﻧﻴﺔ ﻣـﻊ وﺟـﻮد اﻟﻌﺪﻳـﺪ ﻣـﻦ اﻟﻔﺌﺎت اﻟﻔﺮﻋﻴﺔ ﺑﻴﻨ ﻬ ﺎ وﻣﻊ ذﻟﻚ ﻓﺈن ا ﺠـﺮات ﻋﺒﺎرة ﻋﻦ أﺟﺮام دﻳﻨﺎﻣﻴﻜﻴـﺔ ﺗﺘﻄـﻮر ﺑﻤـﺮور اﻟﻮﻗﺖ أﺛﻨﺎ ء ﺗﻔﺎﻋﻠﻬﺎ ﻣﻊ اﻟﺒﻴﺌﺔ ا ﺤﻴﻄـﺔ ﺑﻬـﺎ ﻣﻤﺎ ﻳﻌﻨﻲ أن ا ﺠﺮة اﻟﻔﺮدﻳﺔ ﻗﺪ ﺗﻨﺪرج ﺗﺤـﺖ ﺗﺼﻨﻴﻔﺎت ﻣﺘﻌﺪدة ﻃﻮال ﺣﻴﺎﺗﻬﺎ . ﻳُﻌﺘﻘﺪ أن ﻫﺬا ﻫﻮ اﻟﺤـﺎل ﻣـﻊ ا ﺠـﺮة NGC 4753 اﻟﺘﻲ ﻳﻔﱰض ﻋﻠﻤﺎء اﻟﻔﻠﻚ أﻧﻬـﺎ ﺑـﺪأت ﻛﻤﺠﺮة ﻋﺪﺳﻴﺔ ﻋﺎدﻳﺔ وﻟﻜﻨﻬﺎ ﺗﺤﻮﻟﺖ إﱃ ﻓﺌﺔ ﻏﺮﻳﺒﺔ أﻛﺜﺮ ﺗﺤﺪﻳﺪ اً ﺑﻌﺪ اﻧﺪﻣﺎﺟﻬﺎ ﻣﻊ ﻣﺠـﺮة ﻗ ﺰﻣـﺔ ﻗﺮﻳﺒـﺔ ﻣﻨـﺬ أﻛﺜـﺮ ﻣـﻦ ﻣﻠﻴـﺎر ﺳـ ﻨﺔ اﻛﺘﺸﻔﻬﺎ ﻋﺎﻟﻢ اﻟﻔﻠ ﻚ وﻳﻠﻴﺎم ﻫ ﺷـﻞ ﰲ ﻋـﺎم 1784 ، ﺗﻈﻬ ـﺮ ا ﺠ ـﺮة NGC 4753 ﺑﻌــﺾ ا ﻴﺰات اﻟﺮاﺋﻌﺔ . ﺗﻈﻬﺮ ﰲ ﻫـﺬه اﻟﺼـﻮرة ا ﻠﺘﻘﻄـﺔ ﺑﻮاﺳـﻄﺔ ﺗﻠﺴﻜﻮب ﺟﻴﻤﻴﻨﻲ ﺳـﺎوث أﺣـﺪ ﺗﻠﺴـﻜﻮﺑﺎت ﻣﺮﺻﺪ ﺟﻴﻤﻴﻨﻲ اﻟـﺪوﱄ اﻟـﺬي ﻳـﺪﻳﺮه ﻣﺨﺘـﱪ ﻧـﻮﻳﺮﻻب اﻟﺘـﺎﺑﻊ ﻮﺳﺴـﺔ اﻟﻌﻠـﻮم اﻟﻮﻃﻨﻴـﺔ ـــــ - ﻣﺎﺭﺱ ﺃﺑﺮﻳﻞ 2 0 2 4 اﻷﻣﺮﻳﻜﻴﺔ ﻓـﺈن ﻣﻤـﺮات اﻟﻐﺒـﺎر ا ﻌﻘـﺪة ﰲ ا ﺠﺮة ﻫﻲ ﻣﺸﻬﺪ ﻳﺴﺘﺤﻖ ا ﺸﺎﻫﺪة . ﺗﺒﻌﺪ ا ﺠـﺮة NGC 4753 ﺣـﻮاﱄ 60 ﻠﻴـﻮن ﻣ ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﰲ ﻛﻮﻛﺒﺔ اﻟﻌﺬراء وﻫﻲ ﻋﻀـﻮ ﰲ ﻣﺠﻤﻮﻋـﺔ NGC 4753 ﻣـﻦ ا ﺠـ ﺮات داﺧـﻞ ﺳﺤﺎﺑﺔ اﻟﻌﺬراء اﻟﺜﺎﻧﻴﺔ وﻫﻲ ﺳﻠﺴﻠﺔ ﻣﻜﻮﻧـﺔ ﻣﻦ 100 ﻋﻨﻘﻮد ﻣﺠﺮي ﻋﲆ اﻷﻗـﻞ وﻣﺠـﺮات ﻓﺮدﻳﺔ ﺗﻤﺘـﺪ ﻣـﻦ اﻟﺤﺎﻓـﺔ اﻟﺠﻨﻮﺑﻴـﺔ ﻟﺤﺸـﺪ اﻟﻌﺬراء اﻟﻔﺎﺋﻖ . ا إن ﻤﺮات اﻟﻐﺒﺎر ﻳـﺔ ا ﻤﻴـﺰة اﻟﺘـﻲ ﺗﻈﻬـﺮ ﰲ ا ﺠﺮة NGC 4753 واﻟﺘﻲ ﺗﺒﺪو وﻛﺄﻧ ﻬﺎ ﻣﻠﺘﻮﻳﺔ وﺗﺪور ﺣﻮل ﻧﻮاة ا ﺠـﺮة ﻗـﺪ أﺛـﺎرت اﻫﺘﻤـﺎم ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻟﻔﱰة ﻃﻮﻳﻠﺔ وﻫﻲ ا ﻴـﺰات ﻏـ ا ﻨﺘﻈﻤﺔ اﻟﺘﻲ ﺗﻤﻨﺤﻬﺎ ﺗﺼﻨﻴﻔﻬﺎ اﻟﻐﺮﻳﺐ " ." ﻋﻨﺪ اﻟﻨﻈﺮ إﱃ ﻫ ﺬه ا ﺠﺮة ﻣـﻦ ﺣﺎﻓـﺔ اﻷرض ﺎً ﺗﻘﺮﻳﺒ ﻳﻤﻜﻦ أن ﺗﺒﺪو ﻣﺤ ة إﱃ ﺣﺪ ﻣﺎ . ﻟﻜﻦ ﰲ ﻋﺎم 1992 ﻧﴩ ﻓﺮﻳﻖ ﻣﻦ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﺑﻘﻴﺎدة ﺗﻮم ﺳﺘﻴﻤﺎن ﻛﺎﻣ ون وﻫﻮ اﻵن ﻋﺎﻟﻢ أﺑﺤﺎث ﻛﺒ ﰲ ﺟﺎﻣﻌﺔ إﻧﺪﻳﺎﻧﺎ ، دراﺳﺔ ﻣﻔﺼﻠﺔ ﻦﻋ ا ﺠﺮة NGC 4753 وﺟﺪوا ﻓﻴﻬﺎ أن ﺷﻜﻠﻬﺎ ا ﻌﻘﺪ ﻣﻦ ا ﺤﺘﻤﻞ أن ﻳﻜﻮن ﻧﺘﻴﺠـﺔ اﻧـﺪﻣﺎج ﻣﻊ ﻣﺠﺮة رﻓﻴﻘﺔ ﺻﻐ ة . ﻗﺎل ﺳﺘﻴﻤﺎن ﻛـﺎﻣ ون إن " : ا ﺠـﺮات اﻟﺘـﻲ ﺗﻘﻮم ﺑﺎﻟﺘﻬﺎم اتﻣﺠﺮ أﺧﺮى ﻫـﻲ ﻏﺎﻟﺒـ ﺎ ﻣـﺎ ﺗﺒﺪو وﻛﺄﻧﻬﺎ ﺑﻘﺎﻳﺎ ﺣﻄﺎم وﻫﺬا ﻣﺎ ﻳﻨﻄﺒﻖ ﻋﲆ ا ﻫﺬه ."ﺠﺮة