Free Astronomy Magazine March-April 2023 ARABIC VERSION

A uate student at Harvard ndrew Saydjari, a grad- University, researcher at the Center for Astrophysics | Harvard & Smithsonian and lead author of the study. trove of data from DECaPS was re- leased in 2017, and with the addition of the new data release, the survey now covers 6.5% of the night sky and spans a staggering 130 degrees in length. While it might sound mod- est, this equates to 13,000 times the angular area of the full Moon. The DECaPS2 dataset is available to the entire scientific community and is hosted by NOIRLab’s Astro Data Lab, which is part of the Community Science and Data Center. Interactive access to the imaging with panning/ zooming inside of a web-browser is available from the Legacy Survey Viewer, the World Wide Telescope and Aladin. Most of the stars and dust in the Milky Way are located in its disk — the bright band stretching across this image — in which the spi- ral arms lie. While this profusion of stars and dust makes for beautiful images, it also makes the Galactic plane challenging to observe. The dark tendrils of dust seen thread- ing through this image absorb star- light and blot out fainter stars entirely, and the light from diffuse nebulae interferes with any attempts to measure the brightness of individ- ual objects. Another challenge arises from the sheer number of stars, which can overlap in the image and make it difficult to disentangle indi- vidual stars from their neighbors. De- spite the challenges, astronomers delved into the Galactic plane to gain a better understanding of our Milky Way. By observing at near-in- frared wavelengths, they were able to peer past much of the light-ab- sorbing dust. The researchers also used an innovative data-processing approach, which allowed them to better predict the background be- hind each star. This helped to miti- gate the effects of nebulae and crowded star fields on such large as- tronomical images, ensuring that the final catalog of processed data is more accurate. “One of the main reasons for the success of DECaPS2 is that we simply pointed at a region with an extraordinarily high density of stars and were careful about iden- tifying sources that appear nearly on top of each other,” said Andrew Say- djari, a graduate student at Harvard University, researcher at the Center for Astrophysics | Harvard & Smithsonian and lead author of the paper. “Doing so al- lowed us to produce the largest such catalog ever from a single camera, in terms of the number of objects ob- served.” “When combined with im- ages from Pan-STARRS 1, DE- CaPS2 completes a 360-de- gree panoramic view of the Milky Way’s disk and addi- tionally reaches much fainter stars,” said Edward Schlafly, a researcher at the AURA-managed Space Telescope Science Institute and a co-author of the paper describing DECaPS2 published in The Astrophys- ical Journal Supplement . “With this new survey, we can map the three- dimensional structure of the Milky Way’s stars and dust in unprece- dented detail.” “Since my work on the Sloan Digital Sky Survey two decades ago, I have been looking for a way to make better measurements on top of complex backgrounds,” said Douglas Finkbeiner, a professor at the Center for Astrophysics, co-au- thor of the paper, and principal in- vestigator behind the project. “This work has achieved that and more!” “This is quite a technical feat. Imag- ine a group photo of over three billion people and every single in- dividual is recognizable!” says De- bra Fischer, division director of As- tronomical Sciences at NSF. “As- tronomers will be poring over this detailed portrait of more than three billion stars in the Milky Way for decades to come. This is a fantastic example of what partnerships across federal agencies can achieve.”     ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ٢٠ ) إن DECaPS2 ( ﻫﻮ ﻣﺴﺢ ﺴﺘﻮى ﻣﺠـﺮة درب اﻟﺘﺒﺎﻧﺔ ﻛﻤﺎ ﻳُﺮى ﻣﻦ اﻟﺴﻤﺎء اﻟﺠﻨﻮﺑﻴـﺔ ﻣﺄﺧﻮذًا ﺑﺄﻃﻮال ﻣﻮﺟﻴﺔ ﺑﴫﻳﺔ وﻗﺮﻳﺒﺔ ﻣـﻦ اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء . ﺗﻢ إﺻﺪار ا ﺠﻤﻮﻋـﺔ اﻷوﱃ ﻣﻦ اﻟﺒﻴﺎﻧﺎت ﻣـﻦ (DECaPS) ﰲ ﻋـﺎم ٢٠١٧ ، وﻣﻊ إﺿﺎﻓﺔ إﺻﺪار اﻟﺒﻴﺎﻧﺎت اﻟﺠﺪﻳـﺪ ﻳﻐﻄﻲ ا ﺴـﺢ اﻵن ٦.٥ ٪ ﻣـﻦ ﺳـﻤﺎء اﻟﻠﻴـﻞ وﻳﻤﺘﺪ ﺑﻄﻮل ١٣٠ درﺟﺔ ﻣﺬﻫﻞ . ﰲ ﺣ أﻧـﻪ ﻗﺪ ﻳﺒﺪو ﻣﺘﻮاﺿﻌﺎ ، ﻓﺈن ﻫﺬا ﻳﻌـﺎدل ١٣٠٠٠ ﻣﺮة ﻣﻦ ا ﺴﺎﺣﺔ اﻟﺰاوﻳﺔ ﻟﻠﻘﻤﺮ اﻟﺒﺪر ﺗﺘـﻮﻓﺮ ﻣﺠﻤﻮﻋـﺔ ﺑﻴﺎﻧـﺎت DECaPS2) ( ﻟﻠﻤﺠﺘﻤـﻊ اﻟﻌﻠﻤﻲ ﺑﺄﻛﻤﻠﻪ وﻳﺘﻢ اﺳﺘﻀـﺎﻓﺘﻬﺎ ﺑﻮاﺳـﻄﺔ ﻣﺨﺘﱪ اﻟﺒﻴﺎﻧﺎت Astro اﻟﺘﺎﺑﻊ ﺨﺘﱪ ﻧﻮﻳﺮﻻب واﻟﺬ ي ﻳﻌﺪ ﺟﺰءًا ﻣﻦ ﻣﺮﻛـﺰ ﻋﻠـﻮم ا ﺠﺘﻤـﻊ واﻟﺒﻴﺎﻧﺎت . ﻳﺘﻮﻓﺮ اﻟﻮﺻﻮل اﻟﺘﻔـﺎﻋﲇ إﱃ ﺗﻠـﻚ اﻟﺒﻴﺎﻧﺎت . ﺗﻮﺟﺪ ﻣﻌﻈـﻢ اﻟﻨﺠـﻮم واﻟﻐﺒـﺎر ﰲ ﻣﺠﺮة درب اﻟﺘﺒﺎﻧﺔ ﰲ ﻗﺮﺻﻬﺎ اﻟﴩﻳﻂ اﻟﻼﻣﻊ ا ﻤﺘﺪ ﻋﱪ ﻫﺬه اﻟﺼﻮرة ﺣﻴـﺚ ﺗﻮﺟـﺪ اﻷذرع اﻟﺤﻠﺰوﻧﻴﺔ، ﰲ ﺣ أن ﻫﺬه اﻟﻮﻓﺮة ﻣﻦ ا ﻟﻨﺠﻮم واﻟﻐﺒﺎر ﺗﺼﻨﻊ ﺻﻮرًا ﺟﻤ ﻴﻠـﺔ ﺎ ﺗ ﻓﺈﻧﻬـ ﺠﻌـﻞ أﻳﻀًﺎ ﻣﺴﺘﻮى ا ﺠﺮة ﺻﻌﺐ اﻟﺮﺻﺪ . ﺗﻤـﺘﺺ اﴍﻃــﺔ اﻟﻐﺒــﺎر ا ﻈﻠﻤ ـﺔ اﻟﺘ ـﻲ ﺷـﻮﻫﺪت ــــــــ ﻣﺎرس أﺑﺮﻳﻞ 2023 وﻫﻲ ﺗﺨﱰق ﻫـﺬه اﻟﺼـﻮرة ﺿـﻮء اﻟﻨﺠـﻮم وﺗﻤﺴﺢ اﻟﻨﺠﻮم اﻟﺨﺎﻓﺘﺔ ﺗﻤﺎﻣًـﺎ ، وﻳﺘـﺪاﺧﻞ اﻟﻀﻮء اﻟﺼﺎدر ﻋﻦ اﻟﺴﺪم ا ﻨﺘﴩـة ﻣـﻊ أي . ﻣﺤﺎوﻻت ﻟﻘﻴﺎس ﺳﻄﻮع اﻷﺟﺮام اﻟﻔﺮدﻳـﺔ . ﻳﻨﺸﺄ ﺗﺤﺪٍ آﺧﺮ ﻣﻦ اﻟﻌـﺪد اﻟﻬﺎﺋـﻞ ﻟﻠﻨﺠـﻮم ، واﻟﺘﻲ ﻳﻤﻜﻦ أن ﺗﺘﺪاﺧﻞ ﰲ اﻟﺼـﻮرة وﺗﺠﻌـﻞ ﻣﻦ اﻟﺼـﻌﺐ ﻓﺼـﻞ اﻟﻨﺠـﻮم اﻟﻔﺮدﻳـﺔ ﻋـﻦ ﺟ اﻧﻬﺎ ﻋـﲆ اﻟـﺮﻏﻢ ﻣـﻦ اﻟﺘﺤـﺪﻳﺎت ﺗﻮﻏـﻞ ﻋ ﻠﻤﺎء اﻟﻔﻠﻚ ﰲ ﻣﺴﺘﻮى ا ﺠﺮة ﻻﻛﺘﺴﺎب ﻓﻬﻢ أﻓﻀـﻞ ﺠﺮﺗﻨ ـﺎ درب اﻟﺘﺒﺎﻧـﺔ . ﻟﻘـﺪ ﺗﻤﻜـﻦ اﻟﻌﻠﻤﺎء ﻣﻦ ﺧﻼل ﻣﺮاﻗﺒـﺔ اﻷﻃـﻮال ا ﻮﺟﻴـﺔ اﻟﻘﺮﻳﺒﺔ ﻣﻦ اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ﻣﻦ ﺗﺠﺎوز اﻟﻜﺜ ﻣﻦ اﻟﻐﺒﺎر ا ﻤﺘﺺ ﻟﻠﻀـﻮء . اﺳـﺘﺨﺪم اﻟﺒﺎﺣﺜﻮن أﻳﻀًﺎ أﺳـﻠﻮ ﺑًﺎ ﻣﺒﺘﻜـﺮًا ﰲ ﻣﻌﺎﻟﺠـﺔ اﻟﺒﻴﺎﻧﺎت ﻣﻤﺎ ﺳﻤﺢ ﻟﻬﻢ ﺑﺎﻟﺘ ﻨﺒﺆ ﺑﺸﻜﻞ أﻓﻀﻞ ﺑﺎﻟﺨﻠﻔﻴﺔ اﻟﺨﻠﻔﻴﺔ ﻟﻜﻞ ﻧﺠﻢ . ﺳـﺎﻋﺪ ﻫـﺬا ﰲ اﻟﺘﺨﻔﻴﻒ ﻣﻦ آﺛﺎر اﻟﺴـﺪم وﺣﻘـﻮل اﻟﻨﺠـﻮم ا ﺰدﺣﻤﺔ ﻋـﲆ ﻣﺜـﻞ ﻫـﺬه اﻟﺼـﻮر اﻟﻔﻠﻜﻴـﺔ اﻟﻜﺒ ة ، ﻣﻤـﺎ ﻳﻀـﻤﻦ أن ﻳﻜـﻮن اﻟﻔﻬـﺮس اﻟﻨﻬﺎﺋﻲ ﻟﻠﺒﻴﺎﻧﺎت ا ﻌﺎﻟﺠﺔ أﻛﺜﺮ دﻗﺔ . ﻗﺎل أﻧﺪرو ﺳﺎﻳﺪﺟﺎري ﻃﺎﻟﺐ دراﺳﺎت ﻋﻠ ﻴﺎ ﰲ ﺟﺎﻣﻌﺔ ﻫﺎرﻓﺎرد ﺑﺎﺣـﺚ ﰲ ا ﺰ ﻣﺮﻛـ ﻟﻔﻴﺰﻳـﺎء ــــ اﻟﻔﻠﻜﻴﺔ | ﻫﺎرﻓـﺎرد وﺳﻤﻴﺜﺴـﻮﻧﻴﺎن وا ﺆﻟﻒ اﻟﺮﺋﻴﴘ ﻟﻠﻮرﻗﺔ " . ﻟﻘﺪ أﺗـﺎح ﻟﻨﺎ اﻟﻘﻴﺎم ﺑﺬﻟﻚ إﻧﺘﺎج أﻛـﱪ ﻓﻬـﺮس ﻣﻦ ﻫﺬا اﻟﻘﺒﻴـﻞ ﻋـﲆ اﻹﻃـﻼق ﻣـﻦ ﻛـﺎﻣ ا واﺣـﺪة ، ﻣـﻦ ﺣﻴـﺚ ﻋـﺪد اﻷﺷﻴﺎء اﻟﺘـﻲ ﻳـﺘﻢ رﺻـﺪﻫﺎ ." ﻗـﺎل إدوارد ﺷ ـﻼﻓﲇ اﻟﺒﺎﺣ ـﺚ ﰲ ﻣﻌﻬ ـﺪ ﻋﻠﻮم ﺗﻠﺴﻜﻮب اﻟﻔﻀﺎء اﻟﺬي ﺗـﺪﻳﺮه راﺑﻄﺔ اﻟﺠﺎﻣﻌﺎت ﻷﺑﺤﺎث ﻋﻠﻢ اﻟﻔﻠﻚ و ﻣﺆﻟـﻒ ﻣﺸـﺎرك ﰲ اﻟﻮرﻗـﺔ اﻟﺘـﻲ ﺗﴩح اﻹﺻﺪار اﻟﺜﺎﻧﻲ ﻟﺒﻴﺎﻧﺎت ﻣﺴﺢ ﻣﺴـﺘﻮى ا ﺠـﺮة DECaPS2) ( ا ﻨﺸـﻮرة ﰲ ﻣﻠﺤﻖ ﻣﺠﻠﺔ اﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴﺔ، ﻣﻦ ﺧﻼل ﻫﺬا ا ﺴﺢ اﻟﺠﺪﻳﺪ ﻳﻤﻜﻨﻨﺎ رﺳـﻢ ﺧﺮﻳﻄـﺔ ﻟﻠﺒﻨﻴـﺔ ﺛﻼﺛﻴـﺔ اﻷﺑﻌـﺎد ﻟﻨﺠـﻮم وﻏﺒـﺎر ﻣﺠـﺮة درب اﻟﺘﺒﺎﻧ ـﺔ ﺑﺘﻔﺎﺻـﻴﻞ ﻏ ـ ﻣﺴ ـﺒﻮﻗﺔ ". ﻗــﺎل دوﺟــﻼس ﻓﻴﻨﻜﺒــﺎﻳﻨﺮ اﻷﺳــﺘﺎذ ﰲ ﻣﺮﻛــﺰ اﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴﺔ ، وا ﺆﻟﻒ ا ﺸـﺎرك ﻟﻠﻮرﻗـﺔ ا ﻟﺒﺤﺜﻴﺔ " : ﻣﻨﺬ ﻋﻤﲇ ﰲ ﻣﺴﺢ ﺳﻠﻮن ا ﻟﺮﻗﻤـﻲ ﻟﻠﺴﻤﺎء ﻗﺒﻞ ﻋﻘﺪﻳﻦ ﻣﻦ اﻟﺰﻣﻦ ﻛﻨـﺖ أﺑﺤـﺚ ﻋﻦ ﻃﺮﻳﻘﺔ ﻹﺟـﺮاء ﻗﻴﺎﺳـ ﺎت أﻓﻀـﻞ ﻓـﻮق اﻟﺨﻠﻔﻴﺎت ا ﻌﻘﺪة " واﻟﺒﺎﺣﺚ اﻟﺮﺋﻴـ ـ ﴘ وراء ا ﴩوع " ﻟﻘﺪ ﺣﻘﻖ ﻫﺬا اﻟﻌﻤﻞ ذﻟﻚ وأﻛﺜـﺮ "! " ﻫﺬا إﻧﺠـﺎز ﺗﻘﻨـﻲ ﻟﻠﻐﺎﻳـﺔ . ﺗﺨﻴـﻞ ﺻـﻮرة ﺟﻤﺎﻋﻴﺔ ﻷﻛﺜﺮ ﻣﻦ ﺛﻼﺛـﺔ ﻣﻠﻴـﺎرات ﺷـﺨﺺ وﻳﻤﻜﻦ اﻟﺘﻌﺮف ﻋﲆ ﻛﻞ ﻓﺮد " ! ﻳﻘـﻮل دﻳـﱪا ﻓﻴﴩ ﻣﺪﻳﺮ ﻗﺴﻢ اﻟﻌﻠﻮم اﻟﻔﻠﻜﻴﺔ ﰲ ﻣﻮﺳﺴﺔ اﻟﻌﻠﻮم واﻟﻮﻃﻨﻴﺔ اﻷﻣﺮﻳﻜﻴﺔ " . ﺳﻴﻨﻈﺮ ﻋﻠﻤﺎء اﻟﻔﻠﻚ ﰲ ﻫﺬه اﻟﺼﻮرة اﻟﺘﻔﺼﻴﻠﻴﺔ ﻷﻛﺜـﺮ ﻣـﻦ ﺛﻼﺛﺔ ﻣﻠﻴﺎرات ﻧﺠـﻢ ﰲ ﻣﺠـﺮة درب اﻟﺘﺒﺎﻧـﺔ ﻟﻌﻘﻮد ﻗﺎدﻣﺔ ﻫﺬ . ا ﻣﺜﺎل راﺋـﻊ ـﺎ ﻳﻤﻜـﻦ أن ﺗﺤﻘﻘﻪ ا ﺸﺎرﻛﺎت ا ﺘﺨﺼﺼﺔ ﻋﱪ اﻟﻮﻛﺎﻻت اﻟﻔﻴﺪراﻟﻴﺔ ا ﺨﺘﻠﻔﺔ . أﻧــــــﺪروﺳــــــ ﺪﺟﺎريﻃﺎﻟــــــﺐدراﺳــــــﺎت ــﺎ ﻓــﻲﺟﺎﻣﻌـــﺔ ﻫﺎرﻓــﺎرد ، ﺎﺣـــﺚ ﻋﻠ ـــــــــــــﺔ ــــــــــــﺎء اﻟﻔﻠﻜ ﻓــــــــــــﻲﻣﺮﻛـــــــــــــﺰاﻟﻔ | ﻫﺎرﻓـﺎرد وﺳﻤ ﺜﺴــﻮﻧ ﺎن واﻟﻤﺆﻟــﻒ اﻟﺮ ﺴﻲ ﻟﻠﺪراﺳﺔ .