Free Astronomy Magazine January-February 2025 ARABIC VERSION

FU Orionis is circled by a disk of material much hotter than expected by NASA/ESA Abigail Major Ray Villard n 1936, astronomers saw a puz- zlingeventintheconstellation Orion: the young star FU Orionis (FUOri)becameahundredtimes brighter in a matter of months. At itspeak,FUOriwasintrinsically100 timesbrighterthanourSun.Unlike anexplodingstarthough,ithasde- clinedinluminosityonlylanguidly sincethen. Now, a team of astronomers has wielded NASA’s Hubble Space Tele- scope’s ultraviolet capabilities to learnmoreabouttheinteractionbe- tween FU Ori’s stellar surface and the accretion disk that has been dumping gas onto the growing star for nearly 90 years. They find that theinnerdisktouchingthestarisex- traordinarily hot—which challenges conventional wisdom. The observations were made with thetelescope’sCOS(CosmicOrigins Spectrograph)andSTIS(SpaceTele- scopeImagingSpectrograph)instru- ments. The data includes the first far-ultraviolet and new near-ultravi- olet spectra of FU Ori. “We were hoping to validate the hottest part of the accretion disk model,todetermineitsmaximum JANUARY-FEBRUARY2025 I ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 44 اﻟﻨ ﻢ أﻓﻮ " ور ﻮﻧ ﺲ " ﻣﺤﺎط ﻘﺮص ﺗﺮا ﻢ ـ ﺷﺪ ﺪ اﻟ ةﺤﺮار : ﻘﻠﻢ أﺑﻴﺠﻴﻞ ﻣﻴﺠﻮرو راي ﻓ ﻼرد و ﺎﻟﺔ ﻧﺎﺳﺎ و ﺎﻟﺔ اﻟﻔﻀﺎء اﻻوروﺑ ﺔ و ﺎﻟﺔ اﻟﻔﻀﺎء اﻟﻜﻨﺪ ﺔ ﺷـﺎﻫﺪ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﰲ ﻋـﺎم 1936 ﺎً ﺣـﺪﺛ اً ﻣﺤ ﰲ ﻛﻮﻛﺒـﺔ اﻟﺠـ ) ﻮزاء Orion ( ﺣﻴـﺚ أﺻﺒﺢ اﻟﻨﺠﻢ اﻟﺼﻐ أ ﻓﻮ ورﻳـﻮﻧﻴﺲ أﻛﺜـﺮ ﺎﺑﻤ ﺎً ﺳﻄﻮﻋ ﺋﺔ ﻣﺮة ﰲ ﻏﻀﻮن أﺷﻬﺮ . ﻋﻨﺪﻣﺎ ﻛﺎن ﻫﺬا اﻟﻨﺠﻢ ذروﺗﻪ ﰲ أﺻﺒﺢ أ ﻛﺜﺮ ﺎً ﺳﻄﻮﻋ ﻣﻦ ﺷﻤﺴﻨﺎ )ﺑـ 100 ( ﻋﲆ و ﺿﻌﻒ ﻋﻜﺲ اﻟﻨﺠﻢ ا ﺘﻔﺠﺮ ﻓﻘﺪ اﻧﺨﻔﺾﺳﻄﻮ ﻋﻪ ﺑﺒﻂء ﻓﻘﻂ ﻣﻨﺬ ذﻟﻚ اﻟﺤـ اﻵن . اﺳـﺘﺨﺪم ﻓﺮﻳﻖ ﻣﻦ ﻋﻠﻤﺎء اﻟﻔﻠـﻚ ﻗـﺪرات ﺗﻠﺴـﻜﻮب ﻫﺎﺑﻞ اﻟﻔﻀﺎﺋﻲ اﻟﺘﺎﺑﻊ ﻟﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ ﰲ ﻣﺠﺎل اﻷﺷﻌﺔ ﻓﻮق اﻟﺒﻨﻔﺴﺠﻴﺔ ﻌﺮﻓﺔ ا ﺰﻳﺪ ﻋـﻦ اﻟﺘﻔﺎﻋﻞ ﺑ ﺳﻄﺢ اﻟـ ﻨﺠﻢ ﻓـ ﻮ اورﻳـﻮﻧﻴﺲ وﻗﺮص اﻟﱰاﻛﻢ اﻟﺬي ﻛﺎن ﻳﻔﺮغ اﻟﻐـﺎز ﻋـﲆ اﻟﻨﺠﻢ اﻟﻨﺎﻣﻲ ﻣﻨﺬ ﻣﺎ ﻳﻘﺮب ﻣﻦ 90 . ﻋﺎﻣًﺎ ﻟﻘﺪ وﺟﺪ اﻟﻔﺮﻳﻖ اﻟﻌﻠﻤﻲ أن اﻟﻘﺮص اﻟﺪاﺧﲇ اﻟﺬي ﻳﻼﻣﺲ ﻫﺬا اﻟﻨﺠﻢ ﺳﺎﺧﻦ ﺑﺸﻜﻞ ﻏـ ﻋﺎدي وﻫﻮ ﻣﺎ ﻳﺘﺤﺪى اﻟﻨﻈﺮﻳﺎت اﻟﺘﻘﻠﻴﺪﻳﺔ . ﺗﻢ إﺟﺮاء اﻷرﺻﺎد اﻟﻔﻠﻜﻴﺔ ﺑﺎﺳﺘﺨﺪام أﺟﻬﺰة ﻣﻄﻴﺎف اﻷﺻﻮل اﻟ و ﻜﻮﻧﻴﺔ ﻣﻄﻴﺎف اﻟﺘﺼﻮﻳﺮ اﻟﻔﻀﺎﺋﻲ ﻟﻠﺘﻠﺴﻜﻮب . ﺗﺘﻀﻤﻦ اﻟﺒﻴﺎﻧﺎت أول أﻃﻴﺎف ﻓـﻮق ﺑﻨﻔﺴـﺠﻴﺔ ﺑﻌﻴـﺪة وأﻃﻴـ ﺎف ﻗﺮﻳﺒﺔ ﻣﻦ اﻷﺷﻌﺔ ﻓـﻮق اﻟﺒﻨﻔﺴـ . ﺠﻴﺔ ﻟـﻪ ﻗﺎﻟﺖ ﻟـ ﻫﻴﻠـ ﻣـﻦ ﻣﻌﻬـﺪ ﻛﺎﻟﻴﻔﻮرﻧﻴـﺎ ﻟﻠﺘﻜﻨﻮﻟﻮﺟﻴ ــﺎ ﰲ ﺑﺎﺳـــﺎدﻳﻨ ﺎ ﻛﺎﻟﻴﻔﻮرﻧﻴـــﺎ و ا ﺆﻟﻔﺔ ا ﺸﺎرﻛﺔ ﻟﻠﻮرﻗﺔ اﻟﺒﺤﺜﻴﺔ : ﻛﻨﺎ ﻧﺄﻣﻞ - ﻳﻨﺎﻳﺮ ﻓﺒﺮﺍﻳﺮ 2 0 2 5