Free Astronomy Magazine July-August 2026 ARABIC VERSION

7 he Solar System’s two largest gas giant planets, Jupiter and Saturn, haveextensivebutverydifferent familiesofmoonsorbitingthem.Newsim- ulationsconductedonthePCclusteratthe Center for Computational Astrophysics (CfCA), National Astronomical Observa- tory of Japan (NAOJ) showed that the planet’smagneticfieldplaysaroleincre- ating an environment where the new moonscansurviveandgrow,thusshaping the evolution of the system. Jupiterhasmorethan100reportedmoons, including four large ones (Ganymede, Cal- listo, Io, and Europa). Saturn has morethan 280 reported moons, but only one large one (Titan). So it is a puzzle why Saturn managed to cultivate more moons, but fewer large moons than Jupiter. A team led by Kyoto University, including researchers from institutes in Japan and China, used the PC cluster at CfCA, NAOJ, to simulate the formation of the moon sys- tems around Jupiter and Saturn. This sim- ulation recreated the planets’ internal structure to calculate the thermal evolu- tion of Jupiter and Saturn and how their magnetic fields have varied over time. Moons form from material in a “circum- planetary disk” of gas and dust orbitingthe young planet. The disk nurtures the young moons, but interactions with thediskmaycausethemtofallintotheplanet. The simulations showed that young Jupiter generated a strong planetary magneticfield that created a safe “cavity” around the planet where its young large moons were prevented from migrating too closetotheirhostplanet.YoungSaturnlacked a strong magnetic field, so only one large moon managed to survive. “Testing planet formation theory is some- whatdifficultbecausewehaveonlyour SolarSystemforreference,butthereare multiplesatellitesystemsclosetouswhose detailed characteristics we can observe,” says Yuri I. Fujii, primary author of the re- port announcing these findings. Next, the team is interested in expanding their the- ory to other moons and potential exo- moonsystems.  ﻟـﺪ أﻛـﱪ ﻛـﻮﻛﺒ ﻏـﺎزﻳ ﰲ ﻧﻈﺎﻣﻨـﺎ ﻤﴘﺸـ اﻟـ ا ﺸ ﱰي وزﺣﻞ ﻋﺎﺋﻼت واﺳﻌﺔ ﻣﻦ اﻷ ﻗﻤﺎر إﻻ أن ﻫﺎﺗ ا ﻨﻈﻮﻣﺘ ﺗﺨﺘﻠﻔـﺎن ﺑﺼـﻮرة ﻻﻓﺘـﺔ . ﻓﻘـﺪ أﻇﻬـﺮت ﻣﺤﺎﻛﺎة ﺣﺎﺳﻮﺑﻴﺔ ﺟﺪﻳﺪة أُﺟﺮﻳﺖ ﺑﺎﺳـﺘﺨﺪام ﻋﻨﻘـﻮد اﻟﺤﻮاﺳﻴﺐ ﰲ ﻣﺮﻛـﺰ اﻟﻔﻴﺰﻳـﺎء اﻟﻔﻠﻜﻴـﺔ اﻟﺤﺎﺳـﻮﺑﻴﺔ اﻟﺘﺎﺑﻊ ﻟـﺎ ﺮﺻﺪ اﻟﻔﻠﻜﻲ اﻟﻮﻃﻨﻲ اﻟﻴﺎﺑـﺎﻧﻲ أن ا ﺠـﺎل ا ﻐﻨﺎﻃﻴﴘ ﻟﻠﻜﻮﻛﺐ ﻳﻠﻌﺐ دوراً ﻣﻬﻤﺎً ﰲ ﺗﻬﻴﺌـﺔ ﺑﻴﺌـﺔ ﺗﺴﻤﺢ ﻟﻸﻗﻤ ﺎر اﻟﻨﺎﺷﺌﺔ ﺑﺎﻟﺒﻘﺎء واﻟﻨﻤﻮ وﺑﺎﻟﺘﺎﱄ ﻳﺆﺛﺮ ﰲ ﺗﻄﻮر ﻣﻨﻈﻮﻣﺔ اﻷﻗﻤﺎر ﺑﺄﻛﻤﻠﻬﺎ . ﻳﻀﻢ ا ﺸﱰي أﻛﺜﺮ ﻣﻦ 100 ﻗﻤـﺮ ﻣﻜﺘﺸـﻒ ﺗﺸـﻤﻞ أرﺑﻌﺔ أﻗﻤﺎر ﻛﺒـ ة ﻫـﻲ : ﻏﺎﻧﻴﻤﻴـﺪ وﻛﺎﻟﻴﺴـﺘﻮ وآﻳـﻮ . ﻮروﺑﺎ ﻳو أﻣﺎ زﺣﻞ ﻓﻴﻀﻢ أﻛﺜﺮ ﻣﻦ 280 ﻗﻤﺮاً ﻣﻜﺘﺸﻒ ﻟﻜﻨﻪ ﻻ ﻳﻤﺘﻠﻚ ﺳـﻮى ﻗﻤـﺮ ﻛﺒـ واﺣـﺪ ﻫـﻮ ﺗﻴﺘـﺎن . وﻳﻄﺮح ﻫﺬا اﻟ ﻮاﻗﻊ ﻟﻐﺰاً ﻋﻠﻤﻴﺎً ﻣﻬﻤﺎً : ﻛﻴﻒ ﺗﻤﻜﻦ ز ﺣﻞ ﻣﻦ ﺗﻜﻮﻳﻦ ﻋﺪد أﻛﱪ ﻣﻦ اﻷﻗﻤﺎر ﺑﻴﻨﻤـﺎ أﻧـﺘﺞ أﻗﻤـﺎراً ﻛﺒ ة أﻗﻞ ﺑﻜﺜ ﻣﻘﺎرﻧﺔ ﺑﺎ ﺸﱰي؟ وﻟﻺﺟﺎﺑﺔ ﻋﻦ ﻫﺬا اﻟﺴﺆال أﺟﺮى ﻓﺮﻳﻖ ﺑﺤ ﺜﻲ ﺑﻘﻴﺎدة ﺑﺎﺣﺜ ﻣﻦ ﺟﺎﻣﻌـﺔ ﻛﻴﻮﺗﻮ وﺑﻤﺸﺎرﻛﺔ ﻋﻠ ﻤﺎء ﻣﻦ اﻟﻴﺎﺑﺎن واﻟﺼ ﺳﻠﺴـﻠﺔ ﻣﻦ ا ﺤﺎﻛﺎة اﻟﻌﺪدﻳﺔ ﻟﺘﻜـﻮﻳﻦ أﻧﻈﻤـ ﺔ اﻷﻗﻤـﺎر ﺣـﻮل ا ﺸﱰي وزﺣﻞ ﺑﺎﺳﺘﺨﺪام ا ﻮارد اﻟﺤﺎﺳﻮﺑﻴﺔ ﰲ ﻣﺮﻛـﺰ اﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴﺔ اﻟﺤﺎﺳﻮﺑﻴﺔ . وأﻋﺎدت ﻫـﺬه ا ﺤﺎﻛـﺎة ﺑﻨﺎء اﻟﺒﻨﻴﺔ اﻟﺪاﺧﻠﻴﺔ ﻟﻠﻜﻮﻛﺒ ﺑﻬﺪف ﺣﺴﺎب ﺗﻄﻮرﻫﻤﺎ اﻟﺤﺮاري ورﺻﺪ ﻛﻴﻔﻴﺔ ﺗﻐ ﻣﺠﺎﻟﻴﻬﻤﺎ ا ﻐﻨﺎﻃﻴﺴـﻴ ﻋﱪ اﻟﺰﻣﻦ . ﺗﺘﺸﻜﻞ ا ﻷﻗﻤﺎر ﻣﻦ ﻣﻮاد ﻣﻮﺟﻮدة داﺧﻞ ﻣﺎ »ﺑـ ﻳﻌﺮف اﻟﻘﺮص ا ﺤﻴﻂ ﺑﺎﻟﻜﻮﻛﺐ « وﻫﻮ ﻗﺮص ﻣـﻦ اﻟﻐﺎز واﻟﻐﺒﺎر ﻳﺪور ﺣﻮل اﻟﻜﻮﻛﺐ ﺣﺪﻳﺚ اﻟﺘﻜﻮﻳﻦ ﻌﺪ وﻳ ﻫﺬا اﻟﻘﺮص اﻟﺒﻴﺌﺔ اﻟﺘﻲ ﺗﻨﻤﻮ ﻓﻴﻬﺎ اﻷﻗﻤﺎر اﻟﻮﻟﻴـﺪة إﻻ أن اﻟﺘﻔﺎﻋﻼت ﺑ اﻷﻗﻤﺎر واﻟﻘﺮص ﻗﺪ ﺗﺪﻓﻌﻬﺎ ﺗﺪرﻳﺠﻴﺎً إﱃ اﻟﻬﺠﺮ ة ﻧﺤﻮ اﻟﺪاﺧﻞ ﻣﺎ ﻳﺆدي ﰲ ﺑﻌﺾ اﻟﺤـﺎﻻت إﱃ ﺳﻘﻮﻃﻬﺎ داﺧﻞ اﻟﻜﻮﻛﺐ ﻧﻔﺴﻪ . وأﻇﻬﺮت اﻟﻨﺘـﺎﺋﺞ أن ا ﺸﱰي ﻋﻨﺪ ﺗﻜﻮﻳﻨﻪ ﻛﺎن ﻳﻤﺘﻠﻚ ﻣﺠـﺎﻻً ﻣﻐﻨﺎﻃﻴﺴـﻴﺎً ﻗﻮﻳﺎً أﻧﺸﺄ ﻣﻨﻄﻘﺔ داﺧﻠﻴﺔ آﻣﻨﺔ أو ﻣﺎ ﻳ »ﺸﺒﻪ اﻟﻔﺠﻮة « ﰲ اﻟﻘﺮص ا ﺤﻴﻂ ﺑﻪ ﻣﻨﻌﺖ اﻧﺠﺮاف اﻷ ﻗﻤـﺎر اﻟﻜﺒـ ة اﻟﻨﺎﺷــﺌﺔ ﻧﺤــﻮ اﻟﻜﻮﻛــﺐ وﺳــﺎﻋﺪﻫﺎ ﻋــﲆ اﻟﺒﻘــﺎء واﻻﺳﺘﻤﺮار ﰲ اﻟﻨﻤﻮ وﻟﻜﻦ ﻟﻢ ﻳﻤﺘﻠﻚ زﺣﻞ ﻋﻨﺪ ﺗﻜﻮﻳﻨـﻪ ﻣﺠ ﺎﻻً ﻣﻐﻨﺎﻃﻴﺴﻴﺎً ﺑﺎﻟﻘﻮة ﻧﻔﺴﻬﺎ وﻟﺬﻟﻚ ﺗﻄﻮر اﻟﻘﺮص ا ﺤﻴﻂ ﺑﻪ ﻣﻦ دون ﺗﺸﻜﻞ ﻫﺬه اﻟﻔﺠﻮة ﻣﺎ ﺟﻌﻞ ﻣﻌﻈﻢ اﻷﻗﻤﺎر اﻟﻜﺒ ة ﻋﺮﺿﺔ ﻟﻠﻬﺠﺮة ﻧﺤﻮ اﻟﺪاﺧﻞ وﻓﻘـﺪاﻧﻬﺎ ﻟﻜﻦ ﺗﻤﻜﻦ ﻗﻤﺮ ﻛﺒ واﺣﺪ ﻣﻦ اﻟﻨﺠﺎة وﻫﻮ ﺗﻴﺘﺎن . ﻗﺎل ﻳﻮري آي . ﻓﻮﺟﻴﻲ اﻟﺒﺎﺣﺚ اﻟﺮﺋﻴﺲ ﻟﻠﺪراﺳـﺔ إن »: اﺧﺘﺒﺎر ﻧﻈﺮﻳﺎت ﺗﺸﻜﻞ اﻟﻜﻮاﻛﺐ أﻣﺮ ﺻﻌﺐ إﱃ ﺣﺪ ﻣـﺎ ﻷن ﻟﺪﻳﻨﺎ ﻧﻈﺎﻣﻨﺎ اﻟﺸ ـ ﻤﴘ ﻓﻘﻂ ﻛﻤﺮﺟﻊ ﻣﺒﺎﴍ ﻟﻜﻨﻨﺎ ﻧﻤﺘﻠﻚ ﰲ ا ﻘﺎﺑﻞ ﻋﺪة أﻧﻈﻤﺔ ﻟﻸﻗﻤﺎر ﻗﺮﻳﺒﺔ ﻣﻨﺎ ﻳﻤﻜﻨﻨﺎ رﺻﺪ ﺧﺼﺎﺋﺼﻬﺎ اﻟﺘﻔﺼﻴﻠﻴﺔ ودراﺳﺘﻬﺎ . « رﺳﻢ ﺗﺨ ﻠﻲ ـﺎة اﻟـ ﻟﻠﻤﺤﺎ أُﺟﺮﺖ ﻓﻲﻫﺬا اﻟﺒﺤﺚ ﻟـﺪ. ﻮﻛــــــــﺐ اﻟﻤﺸــــــــ ي ) أﺳــــــــﻔﻞ اﻟ ﻤـــــ ( ﻣﺠـــــﺎﻻً ﻣﻐﻨﺎﻃ ﺴــــــ ﺎً ـــــــــ ﺎً ﻗﻮ ﻳﺤـــــــــﺪث ﺗﺠﻮ ﻔـــــــــ ﺎً ﻓـــــــــﻲ ﻗﺮﺻــــــــﮫ اﻟﻤﺤــــــــ ﻂ ﺎﻟ ﻮﻛــــــــﺐ . ﻔﺘﻘــــــﺮ ﻮﻛــــــﺐ زﺣــــــﻞ ) أﻋﻠــــــﻰ اﻟ ﺴـــــــــــــــــــــﺎر ( إﻟـــــــــــــــــــــﻰﻣﺠـــــــــــــــــــــﺎل ﻣﻐﻨﺎﻃ ﺴـــــــــــــﻲﻗـــــــــــــﻮي ﻟـــــــــــــﺬا ﺘﻄـــــــــــــــﻮرﻗﺮﺻـــــــــــــــﮫ اﻟﻤﺤـــــــــــــــ ﻂ ﺎﻟ ﻮﻛﺐ ﺪون ﺗﺠﻮ ﻒ . [YuriI. Fujii/L-INSIGHT (Kyoto University), Shinichiro Kinoshita] 7