Free Astronomy Magazine May-June 2023 ARABIC VERSION

MAY-JUNE 2023 contrast observations in visible light. “Even when you’ve identified such a one-in-a-million event, it’s still ex- tremely difficult to make these meas- urements,” said Leigh Smith of the University of Cambridge. “The glare from the white dwarf can cause streaks in unpredictable directions, meaning we had to analyse each of Hubble’s observations extremely carefully, and their limitations, to model the event and estimate the mass of LAWD 37.” “The precision of LAWD 37’s mass measurement allows us to test the mass-radius relationship for white dwarfs,” said McGill. “This means testing the theory of degenerate matter (a gas so super-compressed under gravity that it behaves more like solid matter) under the extreme conditions inside this dead star,” he added. The researchers say their re- sults open the door for future event predictions with Gaia data. In addi- tion to Hubble, these alignments can now be detected with the NASA/ESA/CSA James Webb Space Telescope. Because Webb works at infrared wavelengths, the blue glow of a foreground white dwarf looks dimmer in infrared light, and the background star looks brighter. Based on Gaia’s predictive powers, Sahu is observing another white dwarf, LAWD 66, with Webb. The first observation was made in 2022. More observations will be taken as the deflection peaks in 2024 and then subsides. “Gaia has really changed the game — it’s exciting to be able to use Gaia data to predict when events will happen, and then observe them happening,” said McGill. “We want to continue meas- uring the gravitational microlensing effect and obtain mass measure- ments for many more types of stars.” In his 1915 general theory of relativ- ity, Einstein predicted that when a massive compact object passes in front of a background star, the light from the star would bend around the foreground object because of the warping of space by its gravita- tional field. Exactly a century before this latest Hubble observation, in 1919, two British-organised expeditions to the southern hemisphere first detected this lensing effect during a solar eclipse on 19 May. It was hailed as the first experimental proof of gen- eral relativity — that gravity warps space. However, Einstein was pes- simistic that the effect could ever be detected for stars outside our Solar System because of the precision re- quired. “Our measurement is 625 times smaller than the effect meas- ured at the 1919 solar eclipse,” said McGill.     ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ ٢٨ ﻳﺴﺘﻄﻴﻊ ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﻓﻘﻂ إﺟـﺮاء ﻫـﺬه اﻷﻧﻮاع ﻣﻦ اﻷرﺻﺎد ﻋﺎﻟﻴﺔ اﻟﺘﺒـﺎﻳﻦ ﰲ اﻟﻀـﻮء ا ﺮﺋﻲ . ﻗﺎل ﱄ ﺳﻤﻴﺚ ﻣﻦ ﺟﺎﻣﻌﺔ ﻛﺎﻣﱪﻳﺪج : " ﺣﺘﻰ ﻋﻨﺪﻣﺎ ﺗﻜﻮن ﻗﺪ ﺣﺪ دت ﺣﺪﺛًﺎ واﺣﺪًا ﰲ ا ﻠﻴﻮن ، ﻻ ﻳﺰال ﻣﻦ اﻟﺼﻌﺐ ﻟﻠﻐﺎﻳﺔ ﺻﻨﻊ ﻫﺬه اﻟﺤﺼﻴﻠﺔ . اﻟﻮﻫﺞ ﻣﻦ اﻟﻘﺰم اﻷﺑﻴﺾ ﻳﻤﻜﻦ أن ﻳﺴﺒﺐ ﺧﻄﻮﻃًﺎ ﰲ اﺗﺠﺎﻫﺎت ﻏ ﻣﺘﻮﻗﻌﺔ ﻣﻤﺎ ﻳﻌﻨﻲ أﻧﻪ ﻛﺎن ﻋﻠﻴﻨﺎ ﺗﺤﻠﻴﻞ ﻛﻞ ﻣﻦ ﻣﻼﺣﻈﺎت ﻫﺎﺑﻞ ﺑﻌﻨﺎﻳﺔ ﻓﺎﺋﻘﺔوﻗﻴﻮدﻫﺎ ﻟﻨﻤﺬﺟﺔ اﻟﺤﺪث وﺗﻘـﺪﻳﺮ ﻛﺘﻠـﺔ .LAWD 37 ﻗـﺎل ﻣﺎﻛﺠﻴـﻞ : " ﺗﺴﻤﺢ ﻟﻨﺎ دﻗﺔ ﻗﻴـﺎس اﻟﻜﺘﻠـﺔ LAWD 37 ﺑﺎﺧﺘﺒﺎر اﻟﻌﻼﻗﺔ ﺑ اﻟﻜﺘﻠﺔ وﻧﺼـﻒ اﻟﻘﻄـﺮ ﻟﻸﻗـﺰام اﻟﺒﻴﻀـﺎء ." وأﺿـﺎف " : ﻫـﺬا ﻳﻌﻨـﻲ اﺧﺘﺒﺎر ﻧﻈﺮﻳﺔ ا ﺎدة ا ﺘﺤﻠﻠﺔ ) ﻏﺎز ﻣﻀـﻐﻮط ﺑﺸﺪة ﺗﺤﺖ اﻟﺠﺎذﺑﻴﺔ ﺑﺤﻴﺚ ﻳﺘـ ـ ﴫف ﻣﺜـﻞ ا ﺎدة اﻟﺼﻠﺒﺔ ( ﰲ ﻇﻞ اﻟﻈﺮوف اﻟﻘﺎﺳﻴﺔ داﺧﻞ ﻫﺬا اﻟﻨﺠﻢ ا ﻴﺖ ، ﻳﻘﻮل اﻟﺒﺎﺣﺜﻮن إن ﻧﺘﺎﺋﺠﻬ ﻢ ﺗﻔﺘﺢ اﻟﺒـﺎب ﻟﺘﻨﺒـﺆات اﻷﺣـﺪاث ا ﺴـﺘﻘﺒﻠﻴﺔ ﺑﺒﻴﺎﻧﺎت Gaia . ﺑﺎﻹﺿـﺎﻓﺔ إﱃ ﻫﺎﺑـﻞ ، ﻳﻤﻜـﻦ اﻵن اﻛﺘﺸــﺎف ﻫــﺬه ا ﺤــﺎذاة ﺑﺎﺳــﺘﺨﺪام ﻳﻤﻜﻦ اﻵن ﺑﺒﻴﺎﻧﺎت ا ﺮﻛﺒﺔ ﻏﺎﻳﺎ ﺑﺎﻹﺿﺎﻓﺔ إﱃ ﺗﻠﺴـﻜﻮب ﻫﺎﺑ ـﻞ اﻛﺘﺸـﺎف ﻫـﺬه ا ﺤـﺎذاة ﺑﺎﺳﺘﺨﺪام ﺗﻠﺴﻜﻮب ﺟﻴﻤﺲ وﻳﺐ اﻟﻔﻀـﺎﺋﻲ ﻧﻈﺮًا ﻷﻧ ﻪ ﻳﻌﻤﻞ ﺑﺄﻃﻮال ﻣﻮﺟﺎت اﻷﺷﻌﺔ ﺗ ﺤﺖ اﻟﺤﻤﺮاء ﻓﺈن اﻟﺘﻮﻫﺞ اﻷزرق ﻟﻘﺰم أﺑـﻴﺾ ﰲ ا ﻘﺪﻣﺔ ﻳﺒﺪو ﺑﺎﻫﺘًﺎ ﰲ ﺿـﻮء اﻷﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء وﻳﺒﺪو ﻧﺠﻢ اﻟﺨﻠﻔﻴﺔ أﻛﺜـﺮ إﴍاﻗًـﺎ . اﺳﺘﻨﺎدًا إﱃ ﻗﻮى ا ﺮﻛﺒﺔ ﻏﺎﻳﺎ اﻟﺘﻨﺒﺆﻳﺔ، ﻳﺮاﻗﺐ اﻟﻌﺎﻟﻢ ﺳﺎﻫﻮ ﻗﺰﻣًﺎ أﺑـﻴﺾ آﺧـﺮ LAWD 66 ﺑﻮاﺳﻄﺔ ﺗﻠﺴﻜﻮب وﻳﺐ . ﺗﻢ إﺟـﺮاء اﻷرﺻـﺎد اﻷوﱃ ﰲ ﻋﺎم ٢٠٢٢ . ﺳـﻴﺘﻢ أﺧـﺬ ا ﺰﻳـﺪ ﻣـﻦ اﻷرﺻﺎد ﻣﻊ ذروة اﻻﻧﺤﺮاف ﰲ ﻋﺎم ٢٠٢٤ ﺛﻢ . ﴪـ ﺗﻨﺤ ﻗﺎل ﻣﺎﻛﺠﻴﻞ " : ﻟﻘﺪ ﻏ ت ا ﺮﻛﺒـﺔ ﻏﺎﻳﺎ اﻷﻓﻜﺎر ﺑﺎﻟﻔﻌـﻞ ﻓ ﻤـﻦ ا ﺜـ أن ﺗﻜـﻮن ﻗﺎدرًا ﻋـﲆ اﺳـﺘﺨﺪام ﺑﻴﺎﻧـﺎت ﻏﺎﻳـﺎ ﻟﻠﺘﻨﺒـﺆ ﺑﻤﻮﻋﺪ وﻗﻮع اﻷﺣﺪاث ، ﺛﻢ ﻣﺮاﻗﺒﺔ ﺣﺪوﺛﻬﺎ ." " ﻧﺮﻳـﺪ أن ﻧﻮاﺻـﻞ ﻗﻴـﺎس ﺗـﺄﺛ اﻟﺠﺎذﺑﻴــﺔ اﻟﻌ ﺪﺳﺔ اﻟﺪﻗﻴﻘﺔ واﻟﺤﺼـﻮل ﻋـﲆ ﻗﻴﺎﺳـﺎت ـــــــ اﻟﻜﺘﻠﺔ ﻷﻧﻮاع ﻋﺪﻳﺪة أﺧﺮى ﻣﻦ اﻟﻨﺠﻮم . ﺗﻨﺒﺄ أﻳﻨﺸﺘﺎﻳﻦ ﰲ ﻧﻈﺮﻳﺘﻪ اﻟﻌﺎﻣﺔ ﻟﻠﻨﺴﺒﻴﺔ ﻋﺎم ١٩١٥ ، أﻧﻪ ﻋﻨﺪﻣﺎ ﻳﻤﺮ ﺟﺴﻢ ﻣﻀﻐﻮطﺿﺨﻢ أﻣﺎم ﻧﺠﻢ ﰲ اﻟﺨﻠﻔﻴﺔ ، ﻓﺈن اﻟﻀﻮء اﻟﻘﺎدم ﻣﻦ اﻟﻨﺠﻢ ﺳﻮف ﻳﻨﺤﻨﻲ ﺣﻮل اﻟﺠﺴـﻢ اﻷﻣـﺎﻣﻲ ﺑﺴﺒﺐ اﻟﺘﻮاء اﻟﻔﻀﺎء ﺑﺴﺒﺐ ﻣ ﺠﺎل ﺟﺎذﺑﻴﺘﻪ . ﻗﺒﻞ ﻗﺮن ﺑﺎﻟﻀﺒﻂ ﻣﻦ ارﺻﺎد ﻫﺎﺑﻞ اﻷﺧـ ة اﻛﺘﺸﻔﺖ ﺑﻌﺜﺘﺎن ﺑﺮﻳﻄﺎﻧﻴﺘـﺎن ﻣﻨﻈﻤﺘـﺎن ﰲ ﻋﺎم ١٩١٩ اﻟﱃ إ ﻨﺼﻒ اﻟﺠﻨﻮﺑﻲ ﻟـﻸرض ﻷول ﻣﺮة ﺗﺄﺛ اﻟﻌﺪﺳﺔ ﺧﻼل ﻛﺴﻮف اﻟﺸـﻤﺲ ﰲ ١٩ . ﻣﺎﻳﻮ ﺗﻢ اﻟﱰﺣﻴﺐ ﺑﻪ ﺑﺎﻋﺘﺒﺎره أول دﻟﻴـﻞ ﺗﺠﺮﻳﺒﻲ ﻋﲆ اﻟﻨﺴـﺒﻴﺔ اﻟﻌﺎﻣـﺔ أن اﻟﺠﺎذﺑﻴـﺔ ﺗﺸﻮه اﻟﻔﻀﺎء . وﻣـﻊ ذﻟـﻚ ﻛـﺎن أﻳﻨﺸـﺘﺎﻳﻦ ﻣﺘﺸـﺎﺋﻤًﺎ ﻣـﻦ إﻣﻜﺎﻧﻴ ـﺔ اﻛﺘﺸـﺎف اﻟﺘ ـﺄﺛ ﻟﻠﻨﺠﻮم ﺧﺎرج ﻧﻈﺎﻣﻨﺎ اﻟﺸﻤﴘ ﺑﺴﺒﺐ اﻟﺪﻗﺔ ا ﻄﻠﻮﺑﺔ . ﻗﺎل ﻣﺎﻛﺠﻴﻞ " : ﻗﻴﺎﺳـﻨﺎ ﻫـﻮ ٦٢٥ ﻣﺮة أﺻﻐﺮ ﻣﻦ اﻟﺘـﺄﺛ اﻟـﺬي ﺗـﻢ ﻗﻴﺎﺳـﻪ ﰲ ﻛﺴﻮف اﻟﺸﻤﺲ ﻋﺎم ١٩١٩ ." ــــﻒ ﺗــــﻢ ﻳﻮﺿـــﺢ ﻫــــﺬا اﻟﺮﺳـــﻢ ﻛ اﺳــــﺘﺨﺪام اﻟﻌﺪﺳــــﺔ اﻟﺪﻗ ﻘـــــﺔ ـﻢ ﻗـﺰم أﺑـ ﻟﻘ ﺎس ﻛﺘﻠﺔ ﻧ . ﺾ ـــــــــﺔ ﺗﻮﺿـــــــــﺢ اﻟﻤﺮﻌـــــــــﺎت اﻟﺪاﺧﻠ ـﻒ ﻛ اﻟﻤﻮﺟﻮدة ﻋﻠﻰ اﻟ ﻤـ ـــــــﻢ ﻓـــــــﻲ ﻣـــــــﺮ اﻟﻘـــــــﺰم أﻣـــــــﺎم ﻧ ا ﻠﻔ ﺔ ﻓﻲﻋﺎم ٢٠١٩ . ـاﻟ ﺨﻂ اﻷزرق اﻟﻤﺘﻤـــﻮج ﺘﺘﺒـــﻊ ﺣﺮﻛــــﺔ اﻟﻘـــﺰم اﻟﻈـــﺎﻫﺮة ﻋـــ اﻟﺴـــﻤﺎء ﻤــــــﺎ ﺗُــــــﺮى ﻣــــــﻦ اﻷرض . ﻋﻠـــــــﻰ اﻟـــــﺮﻏﻢ ﻣـــــﻦ أن اﻟﻘـــــﺰم ﺴــــــﻠﻚ ﻣﺴﺎرًا ﻣﺴﺘﻘ ﻤًﺎ ، ﻓﺈن ﺣﺮﻛﺔ اﻷرض أﺛﻨــــــــﺎء دوراﻧﻬـــــــــﺎ ﺣـــــــــﻮل اﻟﺸــــــــــــﻤﺲ ﺗﻀــــــــــــﻔﻲ اﻧﺤﺮاﻓًــــــــــــﺎ ًــﺎ ﻇﺎﻫﺮ ًــﺎ ﺴــ ﺐ اﺧـــﺘﻼف ﺟﻴﺒ اﻟﻤﻨﻈــــــﺮ ) . ﻘــــــﻊ اﻟــــــﻨ ﻢ ﻋﻠـــــــﻰ ﻌــــــﺪ ١٥ ﺳــــــﻨﺔ ﺿــــــﻮﺋ ﺔ ﻓﻘــــــﻂ و ﺎﻟﺘـــــــــــــﺎﻟﻲ ﺘﺤـــــــــــــﺮك ﻤﻌـــــــــــــﺪل أﺳــــــــــــــــــﺮع ﻣﻘﺎﺑــــــــــــــــــﻞ اﻟـــــــــــــــــــ ـ ﺨﻠﻔ ﺔ ــﺔ اﻟﻨ ﻤ (. وﻣــﻊ ﻣــﺮورﻩ ﺑﺠــﻮار ــــﻢ اﻟــــ ﻧ ـ ﺨﻠﻔ ﺔ ا ﺎﻓﺘــــﺔ ، ﻓــــﺈن ـــــﺔ اﻟﻘـــــﺰم ﺸـــــﻮﻩ ﻣﺠــــﺎل ﺟﺎذﺑ ـــــــــــــ اﻟﻔﻀﺎء ) اﻟ ﻤﺎ ﺗﻨ ﺄت ﻨﻈﺮ ﺔ اﻟﻨﺴﺒ ﺔ ا ﻟﻌﺎﻣﺔ ﻷ ﻨﺸﺘﺎﻳﻦ ﻗﺒﻞ ﻗﺮن ﻣﻦ اﻟﺰﻣﺎن ( وﻗﺪ ﺗﻢ ﻗ ﺎسﻫـﺬا اﻻﻧﺤـﺮاف ﺪﻗـﺔ ﻣـﻦ ـــﺔ ﺧــﻼل دﻗـــﺔ ﻫﺎﺑـــﻞ ﻏـــ اﻟﻌﺎد . ـــﺎﻟﻠﻮن اﻟ ﻘـــﺎﻟﻲ وﺿـــﻊ إزاﺣـــﺔ اﻟﻘـــﺰم ﻣﻠــﻮن . ﻨـــﺘﺞ ﻋـــﻦ ﻣﻘـــﺪار اﻻﻧﺤـــﺮافﻛﺘﻠـــﺔ ﻟﻠﻘـــﺰم اﻷﺑ ﺾ ﺗ ﻠـﻎ ٥٦ ﻓـﻲ اﻟﻤﺎﺋـﺔ ﻣـﻦ ﻛﺘﻠـﺔﺷﻤﺴـﻨﺎ ـﺔ ﻟﻨﻈﺮ وﻫـﺬا ﻳـﻮﻓﺮﻧﻈـﺮة ﺛﺎﻗ ـﻮﻳﻦ اﻷﻗـﺰام اﻟﺒ ﻀـﺎء ـﺔ وﺗ ـﺎت ﻨ ﻫـﺬﻩ و ـﻢ ﻣﻨﻔـﺮد ﻏــ ﻘــ ﺲﻓﻴﻬــﺎ ﻋﻠﻤـﺎء اﻟﻔﻠــﻚ ﺸــ ﻞ ﻣ ﺎﺷـﺮﻛﺘﻠــﺔ ﻧ ﻫـﻲ اﻟﻤـﺮة اﻷوﻟـﻰ اﻟـ اﻟﺸـﻤﺲ . ] NASA, ESA, P. McGill (Univ. of California, Santa Cruz and University of Cambridge), K. Sahu (STScI), J. Depasquale - ﻣﺎﻳﻮ ﻳﻮﻧﻴﻮ 2023