Free Astronomy Magazine July-August 2022 ARABIC VERSION

This astrometric microlensing tech- nique provided information on the mass, distance, and velocity of the black hole. The amount of deflec- tion by the black hole’s intense warping of space allowed Sahu’s team to estimate that it weighs seven solar masses. Lam’s team reports a slightly lower mass range, meaning that the object may be either a neutron star or a black hole. They estimate that the mass of the invisible compact object is between 1.6 and 4.4 times that of the Sun. At the high end of this range the object would be a black hole; at the low end, it would be a neutron star. “As much as we would like to say it is definitively a black hole, we must report all allowed so- lutions. This includes both lower mass black holes and possibly even a neutron star,” said Jessica Lu of the Berkeley team. “ Whatever it is, the object is the first dark stellar rem- nant discovered wandering through the galaxy, unacompanied by an- other star” Lam added. This was a particularly difficult meas- urement for the team because there is another bright star that is ex- tremely close in angular separation to the source star. “So it’s like trying to measure the tiny motion of a fire- fly next to a bright light bulb,” said Sahu. “We had to meticulously sub- tract the light of the nearby bright star to precisely measure the deflec- tion of the faint source.” Sahu’s team estimates the isolated black hole is traveling across the galaxy at 160,000 kilometres per hour (fast enough to travel from Earth to the Moon in less than three hours). That’s faster than most of the other neighbouring stars in that region of our galaxy. “Astrometric microlensing is concep- tually simple but observationally very tough,” said Sahu. “Microlens- ing is the only technique available for identifying isolated black holes.” When the black hole passed in front of a background star located 19,000 light-years away in the ga- lactic bulge, the starlight coming toward Earth was amplified for a duration of 270 days as the black hole passed by. However, it took sev- eral years of Hubble observations to follow how the background star’s position appeared to be deflected by the bending of light by the fore- ground black hole. The existence of stellar-mass black holes has been known since the early 1970s, but all of their mass measurements — until now — have been in binary star systems. Gas from the companion star falls into the black hole and is heated to such high temperatures that it emits X- rays. About two dozen black holes have had their masses measured in X-ray binaries through their gravita- tional effect on their companions. Mass estimates range from 5 to 20 solar masses. Black holes detected in other galaxies by gravitational waves from mergers between black holes and companion objects have been as high as 90 solar masses. “Detections of isolated black holes will provide new insights into the population of these objects in the Milky Way,” said Sahu. He expects that his programme will uncover more free-roaming black holes in- side our galaxy. But it is a needle-in- a-haystack search. The prediction is that only one in a few hundred mi- crolensing events are caused by iso- lated black holes. In his 1916 paper on general relativ- ity, Albert Einstein predicted that his theory could be tested by observing the offset in the apparent position of a background star caused by the Sun’s gravity. This was tested by a collaboration led by astronomers Arthur Eddington and Frank Dyson during a solar eclipse on 29 May 1919. Eddington and his colleagues meas- ured a background star being offset by 2 arc seconds, validating Einstein’s theories. These scientists could hardly have imagined that over a century later this same technique would be used — with a then-unimaginable thousandfold improvement in preci- sion — to look for black holes across our galaxy.      F Telescope has provided, for the first time ever, clear evidence for a lone black ollowing six years of meticulous observations, the NASA/ESA Hubble Space hole drifting through interstellar space. This is the first time the mass of an iso- lated black hole has been measured. This video summarizes the discovery. [ESA/ Hubble, ESA, NASA, STScI, Digitized Sky Survey, Nick Risinger (sk ysurvey.org)] أﺑﻠـﻎ ﻓﺮﻳـﻖ ﻻم ﻋـﻦ ﻧﻄـﺎق ﻛﺘﻠـﺔ أﻗـﻞ ﻗﻠـﻴﻼً ﳑـــﺎ ﻳﻌــﲏ أن اﳉﺴـــﻢ ﻗــﺪ ﻳﻜــﻮن إﻣــﺎ ﻧﺠﻤًــﺎ ﻧﻴﻮﺗﺮوﻧﻴًﺎ أو ﺛﻘﺒًﺎ أﺳـﻮد ، ﻟﻘﺪ ﻗـﺪروا أن ﻛﺘﻠـﺔ اﳉﺴــﻢ اﻟ ﻐــﲑ اﳌــﺮﰄ ﺗــﱰا وح ﺑـــﲔ ١.٦ و ٤.٤ ﺿﻌﻒ ﻛﺘﻠﺔ اﻟﺸﻤﺲ ا ، ﻟﻨﻬﺎﻳﺔ اﻟﻌﻠﻴﺎ ﻣﻦ ﻫﺬا اﻟﻨﻄﺎق ﺳﻴﻜﻮن اﳉﺴﻢ ﻋﺒﺎرة ﻋﻦ ﺛﻘـﺐ أﺳﻮد و ، ﰲ اﻟﻨﻬﺎﻳﺔ اﳌﻨ ﺨﻔﻀﺔ ﺳﻴﻜﻮن ﻧﺠﻤًﺎ ﻧﻴﻮﺗﺮوﻧﻴًﺎ ، وﺑﻘﺪر ﻣﺎ ﻧﻮد أن ﻧﻘﻮل ﺄﻧـﻪﺑ ﺛﻘـﺐ أﺳﻮد ﺑﺸﻜﻞ ﻗﺎﻃﻊ ﻳﺠﺐ ﻋﻠﻴﻨﺎ ﻃﺮح ﺟﻤﻴـﻊ اﳊﻠﻮل اﳌﺴﻤﻮح ﺑﻬـﺎ . ) وﻗﺎﻟـﺖ ﺟﻴﺴـﻴﻜﺎ ﻟـﻮ ( ﻣــﻦ ﻓﺮﻳــﻖ ﺑــﲑﻛﲇ إن ﻫــﺬا ﻳﺸــﻤﻞ ﺛﻘﻮﺑًــﺎ ﺳــــﻮداء ﻣﻨﺨﻔﻀــــﺔ اﻟﻜ ﺘﻠــــﺔ ورﲟــــﺎ ﻧﺠﻤًــــﺎ ﻧﻴﻮﺗﺮوﻧﻴًـــﺎ وأﺿـــﺎف : "(ﻻم) أﻳـــﺎ ﻛـــﺎن ﻫـــﺬا اﳉﺴﻢ ﻓﻬﻮ أول ﺑﻘﺎﻳﺎ ﻧﺠﻤﻴﺔ ﻗﺎﲤﺔ ﺗﻜﺘﺸﻒ ﺗﺘ ﺠﻮل اﳌﺠﺮة ﻏﲑ ﻣﺼﺤﻮﺑﺔ ﺑـﻨﺠﻢ آﺧـﺮ ". ﻛـــﺎن ﻫـــﺬا ﻗﻴﺎﺳًـــﺎ ﺻـــﻌﺒًﺎ ﺑﺸـــﻜﻞ ﺧـــﺎص ﺑﺎﻟﻨﺴـﺒﺔ ﻟﻠﻔﺮﻳـﻖ ﻷن ﻫﻨــﺎك ﻧﺠﻤًــﺎ ﺳـﺎﻃﻌًﺎ آﺧـﺮ ﻗﺮﻳـﺐ ﺟـﺪًا ﻣـﻦ اﻟـ ﻨﺠﻢ اﳌﺼـﺪر ﻗـﺎل : " ﺳﺎﻫﻮ ﻟﺬا ﻓﺈن اﻷﻣﺮ أﺷﺒﻪ ﲟﺤﺎوﻟﺔ ﻗﻴـﺎس اﳊﺮﻛــﺔ اﻟﺼــﻐﲑة ﻟﻔﺮاﺷــﺔ ﺑﺠــﻮار ﻣﺼــﺒﺎح ﺿــﻮء ﺳــﺎﻃﻊ " ." ﻛــﺎن ﻋﻠﻴﻨــﺎ أن ﻧﺘﺒــﻊ ﺑﺪﻗــﺔ ﺿــﻮء اﻟــﻨﺠﻢ اﻟﻼﻣــﻊ اﻟﻘﺮﻳــﺐ ﻟــﲄ ﻧﻘــﻴﺲ ﺑﺪﻗـــــــﺔ اﻧﻜﻤـــــــﺎش اﳌﺼـــــــﺪر اﳋﺎﻓــــــــﺖ ". ـ ـــــــــــــــ ـــــــــــ ﻳُ ﻘﺪر ﻓﺮﻳﻖ ﺳﺎﻫﻮ أن اﻟﺜﻘﺐ اﻷﺳـﻮد اﳌﻨﻔـﺮد ﻳﺴﺎﻓﺮ ﻋﱪ اﳌﺠﺮة ﺑﴪـﻋﺔ ١٦٠ أﻟـﻒ ﻛﻴﻠـﻮﻣﱰ ﺑ ﺎﻟﺴـﺎﻋﺔ ) ﴎﻋـﺔ ﻛﺎﻓﻴـﺔ ﻟﻠﺴـﻔﺮ ﻣـﻦ اﻷرض إﱃ اﻟﻘــ أﻗـﻞ ﻣـﻦ ﺛـﻼث ﺳـﺎﻋﺎت ( ﻫــﺬا أﴎع ﻣـﻦ ﻣﻌﻈـﻢ اﻟﻨﺠـﻮم اﳌ ﺠـﺎورة اﻷﺧـﺮى ﺗﻠـﻚ اﳌﻨﻄﻘـﺔ ﳎﺮﺗﻨــﺎ ﺿـﻤﻦ درب اﻟﺘﺒﺎﻧــﺔ ﻗﺎل ﺳﺎﻫﻮ " : اﻟﻌﺪﺳﺔ اﻟﺪﻗﻴﻘﺔ ﺑﺴﻴﻄﺔ ﻣـﻦ اﻟﻨﺎﺣﻴﺔ اﻟﻨﻈﺮﻳـﺔ وﻟﻜﻨﻬـﺎ ﺻـﻌﺒﺔ ﻟﻠﻐﺎﻳـﺔ ﻣـﻦ ﺣﻴـــﺚ اﻟﺮﺻــــﺪ " ." اﻟﻌﺪﺳــــﺔ اﻟﺪﻗﻴﻘــــﺔ ﻫــــﻲ اﻟﺘﻘﻨ ﻴــﺔ اﻟﻮﺣﻴــﺪة اﳌﺘﺎﺣــﺔ ﻟﺘﺤﺪﻳــﺪ اﻟﺜﻘــﻮب اﻟﺴﻮداء اﳌﻨﻔﺮدة، ﻓ ﻌﻨﺪﻣﺎ ﻣﺮ اﻟﺜﻘﺐ اﻷﺳﻮد أﻣــﺎم ﻧﺠــﻢ ﺧﻠﻔــﻪ ﻳﺒﻌــﺪ ﻣﺴــﺎﻓﺔ ﺗﺒﻠــﻎ ١٩٠٠٠ ﺳﻨﺔ ﺿﻮﺋﻴﺔ اﻻﻧﺘﻔﺎخ اﳌﺠﺮي ﰎ ﺗﻀـﺨﻴﻢ ﺿــﻮء اﻟـــﻨﺠﻢ اﻟﻘــﺎدم ﻧﺤــﻮ اﻷرض ﳌــﺪة ٢٧٠ ﻳﻮﻣًــﺎ ﻣــﻊ ﻣــﺮور اﻟﺜﻘــﺐ اﻷﺳــﻮد وﻣــﻊ ذﻟــﻚ ﻓﻘﺪ اﺳﺘﻐﺮق اﻷﻣﺮ ﻋﺪة ﺳـﻨﻮات ﻣـﻦ أرﺻـﺎد ﺗﻠﺴـــﻜﻮب ﻫﺎﺑـــﻞ ﳌﺘﺎﺑﻌـــﺔ ﻛﻴﻔﻴـــﺔ اﻧﺤـــﺮاف ﻣﻮﻗــﻊ اﻟـــ ﻨﺠﻢ ﻋــﻦ ﻃﺮﻳــﻖ اﻧﺤﻨـــﺎء ﺿــﻮءه ﺑﻮاﺳـﻄﺔ اﻟﺜﻘـﺐ اﻷﺳـﻮد ﻋﻨـﺪﻣﺎ ﻣـﺮ أﻣﺎﻣــﻪ ﻟﻘـــﺪ ﻋُـــﺮف وﺟـــﻮد اﻟﺜﻘـــﻮب اﻟﺴـــﻮداء ذات اﻟﻜﺘﻠﺔ اﻟﻨﺠﻤﻴﺔ ﻣﻨﺬ أواﺋﻞ اﻟﺴﺒﻌﻴ ﻴﺎت ﻟﻜﻦ ﺟﻤﻴﻊ ﻗﻴﺎﺳﺎت ﻛﺘﻠﺘﻬﺎ ﺣـﱴ اﻵن ﰎ إﺟﺮاؤﻫـﺎ أ اﻟ ﻷﻧﻈﻤــــــﺔ ﻨﺠﻤﻴــــــﺔ اﻟﺜﻨﺎﺋﻴــــــﺔ ﻓﻘــــــﻂ ــــــــــ ـــــــــــــــــــــــ ـــــــــــــــــــــــــ ﺣﻴــﺚ ﻳﺴــﻘﻂ اﻟﻐــﺎز اﳌﻨﺒﻌــﺚ ﻣــﻦ اﻟــﻨﺠﻢ اﳌﺮاﻓـﻖ اﻟﺜﻘـﺐ اﻷﺳـﻮد وﻳـﺘﻢ ﺗﺴـﺨﻴﻨﻪ إﱃ درﺟﺎت ﺣﺮارة ﻋﺎﻟﻴﺔ ﺑ ﺤﻴﺚ ﺗﻨﺒﻌـﺚ ﻣﻨـﻪ أﺷـــﻌﺔ ﺳـــ ﻨﻴﺔ ، ﰎ ﻗﻴـــﺎس ﻛﺘـــﻞ ﺣـــﻮاﱄ ﻋﴩـﻳﻦ ﻣـﻦ اﻟﺜﻘـﻮب اﻟﺴـﻮداء ﺛﻨﺎﺋﻴـﺎت اﻷﺷﻌﺔ اﻟﺴ ﻨﻴﺔ ﻣـﻦ ﺧـﻼل ﺗـﺄﺛﲑ اﳉﺎ ذﺑﻴـﺔ ﻋﲆ رﻓﺎﻗﻬﺎ . إن ﺗﻘﺪﻳﺮات اﻟﻜﺘﻠﺔ ﺗﱰاوح ﻣﻦ ٥ إﱃ ٢٠ ﻛﺘﻠــــــﺔ ﺷﻤﺴــــــﻴﺔ . ﰎ اﻛﺘﺸــــــﺎف اﻟﺜﻘــــﻮب اﻟﺴــــﻮداء اﳌﺠــــﺮات اﻷﺧــــﺮى ﺑﻮاﺳـــﻄﺔ ﻣﻮﺟــﺎت اﳉﺎذﺑﻴــﺔ اﻟﻨﺎﺗﺠــﺔ ﻋــﻦ اﻻﻧـــــﺪﻣﺎﺟﺎت ﺑـــــﲔ اﻟﺜﻘـــــﻮب اﻟﺴـــــﻮداء واﻷﺟﺴﺎم اﳌﺼﺎﺣ ﺒﺔ ﻟﻬﺎ ﺣﻴﺚ ﺑﻠﻐﺖ ﺣـﻮاﱄ ٩٠ ﻛﺘﻠــــﺔ ﺷﻤﺴــــﻴﺔ . وﻗــــﺎل ﺳــــﺎﻫﻮ إن :" اﻛﺘﺸـــﺎﻓﺎت اﻟﺜﻘـــﻮب ا ﻟﺴـــﻮداء اﳌﻨﻔـــﺮدة ﺳـــﺘﻮﻓﺮ رؤى ﺟﺪﻳـــﺪة ﺣـــﻮل ﺗﻌـــﺪاد ﻫـــﺬه اﻷﺟﺴﺎم ﳎﺮة درب اﻟﺘﺒﺎﻧـﺔ " . إﻧـﻪ ﻳﺘﻮﻗـﻊ أن ﻳﻜﺸـﻒ ﺑﺮﻧﺎﳎـﻪ ﻋـﻦ اﳌﺰﻳـﺪ ﻣـﻦ اﻟﺜﻘـﻮب اﻟﺴـﻮدا ء اﻟـﱵ ﺗﺘﺠـﻮل ﺑﺤﺮﻳـﺔ داﺧـﻞ ﳎﺮﺗﻨـﺎ ﻟﻜﻨﻪ ﺑﺤﺚ ﺑﺈﺑﺮة ﻛﻮﻣﺔ ﻗﺶ ﻓﺎﳌﻜﺘﺸﻒ ﻫﻮ ﺣﺪﺛًﺎ واﺣﺪًا ﻓﻘﻂ ﻣـﻦ ﺑـﲔ ﺑﻀـﻊ ﻣﺌـﺎت ﻣــﻦ أﺣــﺪاث اﻟﻌﺪﺳــﺔ اﻟﺪﻗﻴﻘــﺔ ﻧــﺎﺗﺞ ﻋــﻦ ﺛﻘــﻮب ﺳــﻮداء ﻟﻘــﺪ . ﻣﻨﻔــﺮدة ﺗﻨﺒــﺄ أﻟــﱪت أﻳﻨﺸﺘﺎﻳﻦ ورﻗﺘـﻪ اﻟﺒﺤﺜﻴـﺔ ﻋـﺎم ١٩١٦ ﻋـﻦ اﻟﻨﺴ ﻴﺔ اﻟﻌﺎﻣﺔ ﺑﺄﻧـﻪ ﳝﻜـﻦ اﺧﺘﺒـﺎر ﻧﻈﺮﻳﺘـﻪ ﻣــــﻦ ﺧــــﻼل ﻣﺮاﻗﺒــــﺔ اﻹزاﺣــــﺔ اﳌﻮﻗــــﻊ اﻟﻈﺎﻫﺮي ﻟﻨﺠﻢ اﳋﻠﻒ وه ﺗـﺄﺛﲑ ﺗﺘﺴـ ﺐ ﺑﺤﺪوﺛـﻪ ﺟﺎذﺑﻴـﺔ اﻟﺸـﻤﺲ . ﰎ اﺧﺘﺒـﺎر ذﻟـﻚ ﻣـﻦ ﺧـﻼل ﺗﻌـﺎون ﺑﻘﻴـﺎدة ﻋﺎﳌـﺎ اﻟﻔﻠـ ﻚ آرﺛـﺮ ﻐ إدﻳﻨ ﺘـﻮن وﻓﺮاﻧـﻚ داﻳﺴـﻮن أﺛ ﻨـﺎء ﻛﺴـﻮف ﻟﻠﺸﻤﺲ ٢٩ ﻣﺎﻳﻮ ١٩١٩ اﻟﺘـﺎرﻳﴠ ﺣﻴـﺚ ﻗﺎم إدﻳﻨ ﻐ ﺘﻮن وزﻣﻼؤه ﺑﻘﻴﺎس ﻧﺠـﻢ ﺧﻠـﻒ اﻟﺸــﻤﺲ . ﻟﻠﺘﺤﻘـــﻖ ﻣــﻦ ﺻــﺤﺔ ﻧﻈﺮﻳــﺎت أﻟــﱪت أﻳﻨﺸــﺘﺎﻳﻦ ﱂ ﻳﻜــﻦ ﺑﺈﻣﻜــﺎن ﻫــﺆﻻء اﻟﻌﻠﻤﺎء ﺗﺨﻴـﻞ أﻧـﻪ ﺑﻌـﺪ أﻛـﱶ ﻣـﻦ ﻗـﺮن ﻣـﻦ اﻟﺰﻣـــﺎن ﺳـــ ﺘﻢ اﺳـــﺘﺨﺪام ﻫـــﺬه اﻟﺘﻘﻨﻴـــﺔ اﻟﻘﺪﳝــﺔ ﻧﻔﺴــﻬﺎ وﻟﻜــﻦ ﻣــﻊ ﺗﺤﺴـﻦ اﻟﺪﻗــﺔ اﻟـــﺬ ي ﱂ ﻳﻜــﻦ ﻣــﻦ اﳌﻤﻜــﻦ ﺗﺨﻴﻠــﻪ آﻧـــﺬاك ﻟﻠﻘﻴـــﺎم ﺎﺑ ﻟﺒﺤـــﺚ ﻋـــﻦ اﻟﺜﻘــــﻮب اﻟﺴـــﻮداء اﳌﻨ ﴩة ﻋﱪ ﳎﺮﺗﻨﺎ درب اﻟﺘﺒﺎﻧﺔ . ﻌــﺪ ﺳـــﺖﺳـــﻨﻮاتﻣــﻦ اﻷرﺻـــﺎد اﻟﺪﻗ ﻘـــﺔ ، ﻗــﺪم ﺗﻠﺴــ ﻮبﻫﺎﺑـــﻞ اﻟﻔﻀــﺎﺋﻲﻷول ﻣـــﺮة ﻋﻠـــﻰاﻹﻃـــﻼق دﻟـــ ﻼً واﺿـــﺤًﺎ ﻋﻠـــﻰوﺟـــﻮد ﺛﻘـــﺐ أﺳـــﻮد ﻣﻨﻔـــﺮد ﻨـــﺪﻓﻊ ﻋـــ اﻟﻔﻀـــﺎ اﻟﻨﺠـــﻮم ء ﺑـــ و ، ﻫـــﺬﻩﻫـــﻲاﻟﻤـــﺮة ـﺎسﻛﺘﻠـﺔ ﺛﻘــﺐ أﺳـﻮد ـﺘﻢﻓﻴﻬـﺎ ﻗ اﻷوﻟـﻰاﻟـ . ﻣﻨﻔـﺮد [ESA/Hubble, ESA, NASA, STScI, Digitized Sky Survey, Nick Risinger (skysurvey.org )] ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ﻳﻮﻟﻴﻮ – أﻏﺴﻄﺲ 2022 ٢٩