Free Astronomy Magazine November-December 2023 ARABIC VERSION

tromagnetic radiation into space. As it rotates, this beam sweeps across the cosmos — much like a light- house beam scanning its surround- ings — and is detected by as- tronomers as it intersects the line of sight to Earth. This makes the star appear to pulse in brightness as seen from our planet. PSR J1023+0038, or J1023 for short, is a special type of pulsar with a bizarre behaviour. Located about 4500 light-years away in the Sextans constellation, it closely orbits an- other star. Over the past decade, the pulsar has been actively pulling mat- ter off this companion, which accu- mulates in a disc around the pulsar and slowly falls towards it. Since this process of accumulating matter began, the sweeping beam virtually vanished and the pulsar started incessantly switching be- tween two modes. In the ‘high’ mode, the pulsar gives off bright X- rays, ultraviolet and visible light, while in the ‘low’ mode it’s dimmer at these frequencies and emits more radio waves. The pulsar can stay in each mode for several seconds or minutes, and then switch to the other mode in just a few seconds. This switching has thus far puzzled astronomers. “Our unprecedented observing cam- paign to understand this pulsar’s be- haviour involved a dozen cutting- edge ground-based and space- borne telescopes,” says Francesco Coti Zelati, a researcher at the Insti- tute of Space Sciences, Barcelona, Spain, and co-lead author of the paper. The campaign included ESO’s Very Large Telescope (VLT) and ESO’s New Technology Telescope (NTT), which detected visible and near-in- frared light, as well as the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. Over two nights in June 2021, they observed the system make over 280 switches between its high and low modes. “We have dis- covered that the mode switching from the pulsating star, causing the matter to heat up. The system is now in a high mode, glowing brightly in the X-ray, ultraviolet and visible light. Eventually, blobs of this hot matter are removed by the pulsar via the jet. With less hot matter in the disc, the system glows less brightly, switching back into the low mode. While this discovery has unlocked the mystery of J1023’s strange be- haviour, astronomers still have much to learn from studying this unique system and ESO’s telescopes will continue to help astronomers ob- serve this peculiar pulsar. In particu- lar, ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, will offer an unprece- dented view of J1023’s switching mechanisms. “The ELT will allow us to gain key in- sights into how the abundance, dis- tribution, dynamics, and energetics of the inflowing matter around the pulsar are affected by the mode switching behavior,” concludes Ser- gio Campana, Research Director at the INAF Brera Observatory and coauthor of the study.  ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 38 ــــﺔ راﺋﻌــــﺔﺷــــﻤﻠﺖ ﻋــــ ﻤﻠــــﺔ ﻣﺮاﻗ 12 ﺗﻠﺴـــــ ﻮ ﺎً ﻋﻠــــﻰاﻷرضوﻓــــﻲاﻟﻔﻀـــــﺎء ﻤــــﺎ ﻓــــﻲذﻟــــﻚ ﺛﻼﺛــــﺔ ﻣﺮاﻓــــﻖﻟﻠﻤﺮﺻـــــﺪ ـﺪور ﺴـﺮﻋﺔ ﻓﺎﺋﻘـﺔ وﻫـﺬا ـﺖ ـﻢﻣ اﻷوروﺑﻲاﻟـﺠﻨﻮﺑﻲاﻛﺘﺸﻒﻋﻠﻤﺎء اﻟﻔﻠﻚاﻟﺴﻠﻮكاﻟﻐﺮﺐﻟﻠﻨ ﻢاﻟﻨﺎ ﺾوﻫـﻮ ﻧ اﻟﻔ ﺪﻳﻮ ﻠﺨﺺا ﻻﻛﺘﺸﺎف . إن اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ ﻫﻮ ﻧﺠﻢ ﻣﻐﻨﺎﻃﻴﴘ ﻣ ﻴﺖ ﴎﻳﻊ اﻟﺪوران ﻳﺼﺪر ﺷﻌ ﺎً ﺎﻋ ﻣﻦ اﻹ ﺷـﻌﺎع اﻟﻜﻬﺮ وﻣﻐﻨﺎﻃﻴﴘ إﱃ اﻟﻔﻀﺎء أﺛﻨﺎء دوراﻧـﻪ ﻳﻤﺮ ﻫﺬا اﻟﺸﻌﺎع ﻋﱪ اﻟﻜﻮن ﻳﺸـﺒﻪ إﱃ ﺣـﺪ ﻛﺒ ﺷﻌﺎع ا ﻨﺎرة اﻟـﺬي ﻳﻤﺴـﺢ ﻣﺤﻴﻄـﻪ وﻳﻜﺘﺸﻔﻪ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﻋﻨﺪﻣﺎ ﻳﺘﻘﺎﻃﻊ ﻣـﻊ ﺧﻂ اﻟﺒﴫ ﻟﻸرض وﻫﺬا ﻳﺠﻌﻞ اﻟﻨﺠﻢ ﻳﺒﺪو وﻛﺄﻧﻪ ﻳﻨﺒﺾ ﰲ اﻟﺴـﻄﻮع ﻛﻤـﺎ ﻳُـﺮى ﻣـﻦ ﻛﻮﻛﺒﻨـﺎ PSR J1023+0038 أو J1023 و ﻫﻮ ﻧﻮع ﺧﺎص ﻣ ﻦ اﻟﻨﺠﻮم اﻟﻨﺎﺑﻀـﺔ ذات ﺳـﻠﻮك ﻏﺮﻳـﺐ وﻳﺒﻌـﺪ ﺣـﻮاﱄ 4500 ﺳـﻨﺔ ﺿﻮﺋﻴﺔ ﰲ ﻛﻮﻛﺒﺔ اﻟﺴـﺪس وﻳـﺪور ﺑﺸـﻜﻞ ﻗﺮﻳﺐ ﺟﺪاً ﻣ ﻊ ﻧﺠﻢ آﺧﺮ . ﻋﲆ ﻣـﺪى اﻟﻌﻘـﺪ ا ﺎﴈ ﻛﺎن اﻟﻨﺠﻢ اﻟﻨـﺎﺑﺾ ﻳﻘـﻮم ﺑﺴـﺤﺐ ا ﺎدة ﻣﻦ ﻫﺬا اﻟﺮﻓﻴﻖ واﻟﺘﻲ ﺗﱰاﻛﻢ ﰲ ﻗﺮص ﺣﻮل اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ وﺗﺴﻘﻂ ﺑـﺒﻂء ﻧﺤـﻮه ﻣﻨـﺬ أن ﺑـﺪأت ﻋﻤﻠﻴـﺔ ﺗـﺮاﻛﻢ ا ـﺎ دة ﻫـﺬه اﺧﺘﻔﻰ اﻟﺸﻌﺎع اﻟﻜﺎﺳﺢ ﻓ ﺎً ﻌﻠﻴ وﺑـﺪأ اﻟـﻨﺠﻢ اﻟﻨﺎﺑﺾ ﰲ اﻟﺘﺒﺪﻳﻞ ﺑﺎﺳﺘﻤﺮار ﺑ وﺿﻌ ﰲ . اﻟﻮﺿﻊ اﻟﻌـﺎﱄ " " ، ﻳﺼـﺪر اﻟـﻨﺠﻢ اﻟﻨـﺎﺑﺾ أﺷ ـﻌﺔ ﺳــﻴﻨﻴﺔ ﺳــﺎﻃﻌﺔ، وﺿــﻮء ﻓــﻮق أﺷﻌﺔ ﺳﻴﻨﻴﺔ ﺳﺎﻃﻌﺔ وﺿﻮء ﻓﻮق ﺑﻨﻔﺴﺠﻲ ﺿﻮء و ﻣﺮﺋﻲ ﺑﻴﻨﻤﺎ ﰲ اﻟﻮﺿﻊ " ا ـﻨﺨﻔﺾ " ﻳﻜﻮن ﺧﺎﻓﺘﺎً ﻋﻨﺪ ﻫـﺬه اﻟـﱰددات وﻳﺼـﺪر ا ﺰﻳﺪ ﻣﻦ ﻣﻮﺟﺎت اﻟﺮادﻳﻮ . ﻳﻤﻜﻦ أن ﻳﺒﻘـﻰ اﻟﻨﺠﻢ اﻟﻨﺎﺑ ﺾ ﰲ ﻛﻞ وﺿـﻊ ﻟﻌـﺪة ﺛـﻮانٍ أو دﻗﺎﺋﻖ ﺛﻢ ﻳﺘﺤﻮل إﱃ اﻟﻮﺿﻊ اﻵﺧـﺮ ﰲ ﺛـ ﻮانٍ ﻣﻌﺪودة وﻗﺪ ﺣ ﻫﺬا اﻟﺘﺤﻮل ﻋﻠﻤﺎء اﻟﻔﻠـﻚ . ﺣﺘﻰ اﻵن ﻳﻘﻮل ﻓﺮاﻧﺸﻴﺴﻜﻮ ﻛﻮﺗﻲ زﻳﻼﺗﻲ اﻟﺒﺎﺣﺚ ﰲ ﻣﻌﻬﺪ ﻋﻠﻮم اﻟﻔﻀﺎء ﰲ ﺑﺮﺷـﻠﻮﻧﺔ ﺑﺈﺳﺒﺎﻧﻴﺎ واﻟﺮﺋﻴﺲ ا ﺸﺎرك ﺆﻟـﻒ اﻟﻮرﻗـﺔ : " إن ﺣﻤﻠﺘﻨﺎ اﻟﺮﺻﺪﻳﺔ ﻏ ا ﺴـﺒﻮﻗﺔ ﻟﻔﻬـﻢ ﺳﻠﻮك ﻫﺬا اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ ﺗﻀﻤﻨﺖ ﻋ ﴩات ـ اﻟﺘﻠﺴﻜﻮﺑﺎت اﻷرﺿﻴﺔ و اﻟﻔﻀﺎﺋ ﻴﺔ ا ﺘﻄﻮرة ." ﺗﻀﻤﻨﺖ اﻟﺤﻤﻠـﺔ اﻟ ﺘﻠﺴـﻜﻮب اﻟﻜﺒـ ﺟـﺪ اً وﺗﻠﺴﻜﻮب اﻟﺘﻜﻨﻮﻟﻮﺟﻴﺎ اﻟﺠﺪﻳـﺪة ا ﻟﺘـﺎﺑﻌ ﻟﻠﻤﺮﺻﺪ اﻷوروﺑﻲ اﻟﺠﻨﻮﺑﻲ واﻟﺬي اﻛﺘﺸـﻒ اﻟﻀﻮء ا ﺮﺋ ﻲ واﻟﻘﺮﻳﺐ ﻣـﻦ اﻷﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤـﺮاء ﺑﺎﻹﺿـﺎﻓﺔ إﱃ ﻣﺼـﻔﻮف ﻣﺮﺻــﺪ أﺗﻜﺎ ﻣﺎ ا ﻠﻴﻤﱰﻳ ﺗ/ﺔ ﺤـﺖ ا ﻠﻴﻤﱰﻳـ ﺔ اﻟﻜﺒـ ) ﻣﺮﺻﺪ أ ﺎ ( ا ﻌـﺪ ﻳ واﻟﺘﻲ ﺮﺻـ ﺪ اﻷوروﺑـﻲ اﻟﺠﻨﻮﺑﻲ ﴍﻳﻜﺎ ﻓﻴﻪ ﻋـﲆ ﻣـﺪى ﻟﻴﻠﺘـ ﰲ ﻳﻮﻧﻴﻮ 2021 ، ﻻﺣﻈﻮا أن اﻟﻨﻈﺎم ﻳﻘﻮم ﺑﺄﻛﺜﺮ ﻣ ـﻦ 280 ﺗﺒ ـﺪﻳﻼً ﺑ ـ اﻟﻮﺿ ـﻌ اﻟﻌ ـﺎﱄ وا ﻨﺨﻔﺾ . ﻳﻘﻮل ﻛﻮﺗﻲ زﻳﻼﺗـﻲ، ا ﻨﺘﺴـﺐ ﻣﻦ 280 ﺗﺒﺪﻳﻼً ﺑ اﻟﻮﺿﻌ اﻟﻌ ـﺎﱄ وا ـﻨﺨﻔﺾ . ﻳﻘــﻮل ﻛﻮﺗﻲ زﻳﻼﺗﻲ، ا ﻨﺘﺴﺐ أﻳﻀًﺎ إﱃ INAF " : ﻟﻘﺪ اﻛﺘﺸـﻔﻨﺎ أن ﺗﺒ ـﺪﻳﻞ اﻟﻮﺿ ـﻊ ﻳﻨﺒ ـﻊ ﻣ ـﻦ ﺗﻔﺎﻋﻞ ﻣﻌﻘﺪ ﺑ رﻳﺎح اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ وﺗـﺪﻓﻖ اﻟﺠﺴـﻴﻤﺎت ﻋﺎﻟﻴﺔ اﻟﻄﺎﻗـﺔ اﻟﺘـﻲ ﺗﻨﻄﻠـﻖ اً ﺑﻌﻴـﺪ ﻋـﻦ اﻟـﻨﺠﻢ اﻟ ﻨـﺎﺑﺾ وا ﺎدة ا ﺘﺪﻓﻘﺔ ﻧﺤـﻮ اﻟـﻨﺠﻢ اﻟﻨــــﺎﺑﺾ ." ﰲ اﻟﻮﺿــــﻊ ا ﻨﺨﻔﺾ ﻳـﺘﻢ ﻃـﺮد ا ـﺎدة ا ﺘﺪﻓﻘﺔ ﻧﺤﻮ اﻟﻨﺠﻢ اﻟﻨـﺎﺑﺾ ﻔﺎﺛﺔ ﰲ ﺿﻴﻘﺔ ﻣﺘﻌﺎﻣﺪة ﻣﻊ اﻟﻘﺮص ، ﺗﺪرﻳﺠﻴﺎً ﺗﱰاﻛﻢ ﻫﺬه ا ﺎدة ﺑ ﺸﻜﻞ أﻗﺮب ﻓﺄﻗﺮب إﱃ اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ وﺑﻴﻨﻤﺎ ﻳﺤﺪث ﻫﺬا ﺗﴬﺑﻪ اﻟﺮﻳﺎح اﻟﺘﻲ ﺗﻬﺐ ﻣﻦ اﻟﻨﺠﻢ اﻟ ﻨﺎﺑﺾ ﻣﻤﺎ ﻳﺆدي إ ﱃ ﺗﺴــﺨ ا ــﺎدة . أﺻــﺒﺢ اﻟﻨﻈﺎم اﻵن ﰲ اﻟﻮﺿﻊ اﻟﻌـﺎﱄ ــ وﻳﺘﻮﻫﺞ ﺑﺸﻜﻞ ﺳﺎﻃﻊ ﰲ اﻷﺷﻌﺔ اﻟﺴـﻴﻨﻴﺔ واﻷﺷ ﻌﺔ ﻓﻮق اﻟﺒﻨﻔﺴﺠﻴﺔ واﻟﻀـﻮء ا ﺮﺋـﻲ و ﰲ اﻟﻨﻬﺎﻳﺔ ﺗﺘﻢ إزاﻟﺔ اﻟﻨﻘﻂ ﻣﻦ ﻫﺬه ا ـﺎدة اﻟﺴـﺎﺧﻨﺔ ﺑﻮاﺳـﻄﺔ اﻟـﻨﺠﻢ اﻟﻨـﺎﺑﺾﻋـﱪ اﻟﻨﻔﺎﺛ و ﺔ ﻣﻊ وﺟﻮد ﻛﻤﻴـﺔ أﻗـﻞ ﻣـﻦ ا ـﺎدة اﻟﺴﺎﺧﻨﺔ ﰲ اﻟﻘﺮص ﻳﺘﻮﻫﺞ اﻟﻨﻈﺎم ﺑ ﺸـﻜﻞ أﻗﻞ ﺳﻄﻮﻋ و ﺎً ﻳﻌﻮد ﻣﺮة أﺧـﺮى إﱃ اﻟﻮﺿـﻊ ا ﻨﺨﻔﺾ إ . ن ﻫﺬا اﻻﻛﺘﺸﺎف ﻗﺪ ﻛﺸﻒ ﻟﻐﺰ ﺳﻠﻮك J1023 اﻟﻐﺮﻳﺐ وﻟﻜﻦ ﻻ ﻳـﺰال أﻣـﺎم اﻟ ﻌﻠﻤﺎء اﻟﻜﺜ ﻟﻴﺘﻌ ﻠﻤﻮه ﻣـﻦ دراﺳـﺔ ﻫـﺬا اﻟﻨﻈﺎم وﺳﺘﺴﺘﻤﺮ اﻟ ﺘﻠﺴﻜﻮﺑﺎت ﰲ ﻣﺮاﻗﺒـﺔ ﻫــﺬا اﻟ ـﻨﺠﻢ اﻟﻨ ـﺎﺑﺾ اﻟﻐﺮﻳــﺐ . ﺳ ـﻴﻘﺪم اﻟﺘﻠﺴﻜﻮب اﻟﻜﺒ ﻟﻠﻐﺎﻳـﺔ اﻟﺘـﺎﺑﻊ ﻟﻠﻤﺮﺻـﺪ اﻷوروﺑﻲ اﻟﺠﻨﻮﺑﻲ واﻟﺬي ﻫﻮ ﻗﻴـﺪ اﻹﻧﺸـﺎء ﺎً ﺣﺎﻟﻴ ﰲ ﺗﺸﻴﲇ رؤﻳﺔ ﻏ ﻣﺴـﺒﻮﻗﺔ ﻵﻟﻴـﺎت اﻟﺘﺒﺪﻳﻞ ﰲ J1023 . ﻳﺨﻠﺺﺳ ﺟﻴﻮ ﻛﺎﻣﺒﺎﻧﺎ ﻣـﺪﻳﺮ اﻷﺑﺤـﺎث ﰲ ﻣﺮﺻـﺪ ﺑﺮﻳـﺮا اﻟﻔﻠﻜـﻲ وا ﺆﻟﻒ ا ﺸـﺎرك ﺑﺎﻟ ﻠﺪراﺳـﺔ :" اﻟﺘﻠﺴـﻜﻮب اﻟﻜﺒ ﻟﻠﻐﺎﻳﺔ ﺳﻴﺴﻤﺢ ﻟﻨﺎ ﺑﺎﻟﺤﺼـﻮل ﻋـﲆ رؤى ﺣـﻮل ﻛﻴﻔﻴ ـﺔ ﺗ ـﺄﺛﺮ وﻓ ـﺮة وﺗﻮزﻳ ـﻊ ودﻳﻨﺎﻣﻴﻜﻴﺔ وﻃﺎﻗﺔ ا ـﺎدة ا ﺘﺪ ﻓﻘـﺔ ﺣـﻮل اﻟﻨﺠﻢ اﻟﻨﺎﺑﺾ ﺑﺴﻠﻮك ﺗﺒﺪﻳﻞ اﻟﻮﺿﻊ ." ﻧﻮﻓﻤﺒﺮ - ﺩﻳﺴﻤﺒﺮ 2 0 2 3