Free Astronomy Magazine September-October 2023 ARABIC VERSION

W ater is essential for life as we know it. However, scientists debate how it reached the Earth and whether the same processes could seed rocky ex- oplanets orbiting distant stars. New insights may come from the plane- tary system PDS 70, located 370 light-years away. The star hosts both an inner disk and outer disk of gas and dust, separated by a 5 billion- mile-wide (8 billion kilometer) gap, and within that gap are two known gas-giant planets. New measurements by NASA’s James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) have de- tected water vapor in the system’s inner disk, at distances of less than 100 million miles (160 million kilo- meters) from the star – the region where rocky, terrestrial planets may be forming. (The Earth orbits 93 mil- lion miles from our Sun.) This is the first detection of water in the ter- restrial region of a disk already known to host two or more proto- planets. “We’ve seen water in other disks, but not so close in and in a system where planets are currently assem- bling. We couldn’t make this type of measurement before Webb,” said lead author Giulia Perotti of the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany. “This discovery is extremely excit- ing, as it probes the region where rocky planets similar to Earth typi- cally form,” added MPIA director Thomas Henning, a co-author on the paper. Henning is co-principal investigator of Webb’s MIRI (Mid-In- frared Instrument), which made the detection, and the principal investi- gator of the MINDS (MIRI Mid-In- frared Disk Survey) program that took the data. PDS 70 is a K-type star, cooler than our Sun, and is estimated to be 5.4 million years old. This is relatively old in terms of stars with planet- forming disks, which made the dis- covery of water vapor surprising. Over time, the gas and dust content of planet-forming disks declines. Ei- ther the central star’s radiation and winds blow out such material, or the dust grows into larger objects that eventually form planets. As previous studies failed to detect water in the central regions of sim- ilarly aged disks, astronomers sus- pected it might not survive the harsh stellar radiation, leading to a dry environment for the formation of any rocky planets. Astronomers haven’t yet detected any planets forming within the SEPTEMBER-OCTOBER 2023 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 29 ﺼﻮرﻫﺬا اﻟﺮﺳﻢ اﻟﺘﺨ ﻠﻲ اﻟﻨ ﻢ PDS 70 اﻟﺪاﺧﻠﻲ وﻗﺮﺻﮫ اﻟ ﻮﻛ . ـﺪة أﺟﺮاﻫـﺎ ﻛﺸـﻔﺖ ﻗ ﺎﺳـﺎتﺟﺪ ﺗﻠﺴ ﻮب ﺟ ﻤﺲو ﺐ اﻟﻔﻀﺎﺋﻲ اﻟﺘـﺎﺑﻊ ﻟ ﻮ ﺎﻟـﺔ ﻧﺎﺳـﺎ ﻋـﻦ ﺑﺨـﺎراﻟﻤـﺎء ﻋﻠـﻰ ﻣﺴـﺎﻓﺎت أﻗـﻞ ﻣـﻦ 100 ﻣﻠﻴـﻮن ﻣﻴﻞ ﻣﻦ اﻟﻨ ﻢ ﻗﺪ ﺗﺘﺸ ﻞ ﻓﻴﻬﺎ اﻟ ﻮاﻛـﺐ اﻟﺼـﺨﺮ ﺔ وﻫﻲ اﻟﻤﻨﻄﻘﺔ اﻟ . ـﺎﻩ ﻫـﺬا ﻫـﻮ أول اﻛﺘﺸـﺎف ﻟﻠﻤ ﻓـﻲ اﻟﻤﻨﻄﻘـﺔ اﻟﺼـﺨﺮ ﺔ ﻟﻘـﺮصﻣﻌــﺮوف ﺎﻟﻔﻌـﻞ أ أو أﻛــ أوﻟﻴـ ــﻮﻛﺒ ﻧــﮫ ﺴﺘﻀـ ﻒ ، ﻈﻬـﺮأﺣــﺪﻫﻤﺎ ﻓﻲ أﻋﻠﻰ اﻟ ﻤ . [NASA, ESA, CSA, Joseph Olmsted (STScI)] ا ء ﺎ ـــ ﺔﴐورﻳ ﻟﻠﺤﻴﺎة ﻛﻤﺎ ﻧﻌﺮف وﻣـﻊ ذﻟﻚ ﻳﻨﺎﻗﺶ اﻟﻌﻠﻤﺎء ﻛﻴﻒ وﺻـﻠﺖ إﱃ اﻷرض وﻣﺎ إذا ﻛﺎﻧﺖ ﻧﻔﺲ اﻟﻌﻤﻠﻴﺎت ﻳﻤﻜﻦ أن ﺗﺰرع ﻛﻮاﻛﺐ ﻧﺠﻤﻴﺔ ﺻﺨﺮﻳﺔ ﺗـﺪور ﺣـﻮل ﻧﺠـﻮم . ﺑﻌﻴﺪة ﻗﺪ ﺗـﺄﺗﻲ رؤى ﺟﺪﻳـﺪة ﻣـﻦ اﻟﻨﻈـﺎم اﻟﻜﻮﻛﺒﻲ PDS 70 اﻟـﺬي ﻳﺒﻌـﺪ 370 ﺳـﻨﺔ . ﺿﻮﺋﻴﺔ ﻳﺴﺘﻀـﻴﻒ اﻟـﻨﺠﻢ ﻗﺮﺻـﺎً ﻠﻴـﺎً داﺧ ﺎً وﻗﺮﺻ ﺎً ﺧﺎرﺟﻴ ﻣﻦ اﻟﻐـﺎز واﻟﻐﺒـﺎر ﺗﻔﺼـﻞ ﺑﻴﻨﻬﻤﺎ ﻓﺠﻮة ﻳﺒﻠﻎ ﻋﺮﺿﻬﺎ 5 ﻣﻠﻴـﺎرات ﻣﻴـﻞ )8 ﻣﻠﻴﺎرات ﻛﻴﻠـﻮﻣﱰ ( وﻳﻮﺟـﺪ ﺿـﻤﻦ ﺗﻠـﻚ اﻟﻔﺠﻮة ﻛﻮﻛﺒـﺎن ﻣﻌﺮوﻓـﺎن ﻣـﻦ اﻟﻜﻮاﻛـﺐ اﻟﻐﺎزﻳﺔ اﻟﻌﻤﻼﻗﺔ . ﻛﺸـﻔﺖ ﻗﻴﺎﺳـﺎت ﺟﺪﻳـﺪة أﺟﺮﺗﻬـﺎ ﻛـﺎﻣ ا ) ﻣ ي أداة اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ا ﺘﻮﺳﻄﺔ ( ﻟﺘﻠﺴﻜﻮب ﺟـﻴﻤﺲ وﻳـﺐ اﻟﻔﻀـﺎﺋﻲ اﻟﺘـﺎﺑﻊ ﻟﻨﺎﺳﺎ ﻋﻦ ﺑﺨـﺎ ر ا ـﺎء ﰲ اﻟﻘـﺮص اﻟـﺪاﺧﲇ ﻟﻠﻨﻈﺎم ﻋﲆ ﻣﺴﺎﻓﺎت أﻗﻞ ﻣـﻦ 100 ﻣﻠﻴـﻮن ـــ - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 3 ) ﻣﻴــﻞ 160 ﻣﻠﻴـﻮن ﻛﻴﻠـﻮﻣﱰ ( ﻣــﻦ اﻟـﻨﺠﻢ ا ﻨﻄﻘﺔ اﻟﺘﻲ ﺗﻮﺟﺪ ﻓﻴﻬﺎ ﻛﺘـﻞ ﺻـﺨﺮﻳﺔ ﻗـﺪ ﺗﺘﺸﻜﻞ ) . ﻛﻮاﻛﺐ ﺗﺪور اﻷرضﻋـﲆ ﺑﻌـﺪ 93 ﻣﻠﻴﻮن ﻣﻴﻞ ﻣـﻦ اﻟﺸـﻤﺲ ( وﻫـﺬا ﻫـﻮ أول اﻛﺘﺸﺎف ﻟﻠﻤﻴﺎه ﰲ ا ﻨﻄﻘﺔ اﻟﺼﺨﺮﻳﺔ ﻟﻘﺮص ﻣﻌﺮوف ﺑﺎﻟﻔﻌـﻞ ﺑﺄﻧـﻪ ﻳﺴﺘﻀـﻴﻒ ﻛـﻮﻛﺒ أوﻟﻴ أو أﻛﺜﺮ . ﻗﺎﻟﺖ ا ﺆﻟﻔﺔ اﻟﺮﺋﻴﺴﻴﺔ ﺟﻮﻟﻴﺎ ﺑ وﺗﻲ ﻣﻦ ﻣﻌﻬﺪ ﻣﺎﻛﺲ ﺑﻼﻧﻚ ﻟﻌﻠـﻢ اﻟﻔﻠـﻚ ﰲ ﻫﺎﻳـﺪﻟﱪغ ﺑﺄ ﺎﻧﻴـﺎ :" ﻟﻘـﺪ رأﻳﻨـﺎ ا ـﺎء ﰲ أﻗﺮاص أﺧﺮى وﻟﻜﻦ ﻟﻴﺲ ﻗﺮﻳﺒ اً ﺟﺪ ﺎً ﰲ ﻧﻈﺎم ﺗﺘﺠﻤﻊ ﻓﻴﻪ اﻟﻜﻮاﻛﺐ ﺣﺎﻟﻴ ﺎً ﻟـﻢ ﻧـﺘﻤﻜﻦ ﻣـﻦ إﺟﺮاء ﻫﺬا اﻟﻨﻮع ﻣ ﻦ اﻟﻘﻴﺎس ﻗﺒﻞ ﺗﻠﺴـﻜﻮب ". وﻳﺐ أﺿﺎف ﻣﺪﻳﺮ ﻣﻌﻬﺪ ﻣﺎﻛﺲ ﺑﻼﻧﻚ ﻟﻌﻠﻢ اﻟﻔﻠﻚ ﺗﻮﻣﺎس ﻫﻴﻨﻴﻨﺞ وﻫﻮ ﻣﺆﻟﻒ ﻣﺸﺎرك ﰲ اﻟﻮرﻗﺔ إن : " ﻫـﺬا اﻻﻛﺘﺸـﺎف ﻣﺜـ وﻣﻬـﻢ ﻟﻠﻐﺎﻳﺔ ﻷﻧﻪ ﻳﺴﺘﻜﺸﻒ ا ﻨﻄﻘﺔ اﻟﺘﻲ ﺗﺘﺸـﻜﻞ ﻓﻴﻬﺎ ﻋـﺎدة اﻟﻜﻮاﻛـﺐ اﻟﺼـﺨﺮﻳﺔ ا ﺸـﺎﺑﻬﺔ ـــــ ﻟﻸرض ." ﻫﻴﻨﻴـﻨ ﺞ ﻫـﻮ اﻟﺒﺎﺣـﺚ اﻟﺮﺋﻴـ ﴘ ـ ا ﺸﺎرك ﰲ ﻛﺎﻣ ا ﻣ ي اﻟﺘﺴﻜﻮب وﻳﺐ أد) اة اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ا ﺘﻮﺳﻄﺔ ( اﻟﺘﻲ ﻗﺎﻣﺖ ﺑﺎﻟﻜﺸــﻒ واﻟﺒﺎﺣــﺚ اﻟﺮﺋﻴـ ـ ﴘﰲ ﺑﺮﻧــﺎﻣﺞ ) ﻣﺎﻳﻨ ـﺪز ﻣﺴـﺢ اﻟﻘ ـﺮص ﺑﺎﻷﺷـﻌﺔ ﺗﺤــﺖ اﻟﺤﻤﺮاء ا ﺘﻮﺳﻄﺔ ﺑﻜﺎﻣ ا ﻣ ي ( اﻟﺬي أﺧﺬ اﻟﺒﻴﺎﻧﺎت . PDS 70 ﻫﻮ ﻧﺠﻢ ﻣﻦ اﻟﻨﻮع )K( وﻫﻮ أﻛﺜـﺮ ﺑﺮودة ﻣﻦ اﻟ ﺸـﻤﺲ وﻳﻘـﺪر ﻋﻤـﺮه ﺑــ 5.4 ﻣﻠﻴﻮن ﺳـﻨﺔ وﻫـﺬا ﻗـﺪﻳﻢ ﻧﺴـﺒﻴﺎً ﺑﺎﻟﻨﺴـﺒﺔ ﻟ ﻠﻨﺠﻮم ذات اﻷﻗﺮاص ا ﻜﻮﻧﺔ ﻟﻠﻜﻮاﻛـﺐ ﻣـﺎ ﺟﻌﻞ اﻛﺘﺸﺎف ﺑﺨﺎر ا ﺎء ﻣﻔﺎﺟﺌـﺎً وﺑﻤـﺮور اﻟﻮﻗﺖ ﻳ ﻘﻞ ﻣﺤﺘﻮى اﻟﻐﺎز واﻟﻐﺒﺎر ا ﻮﺟﻮد ﰲ اﻷﻗﺮاص ا ﻜﻮﻧﺔ ﻟﻠﻜﻮاﻛﺐ ﻓﺈﻣـﺎ أن إﺷـﻌﺎع اﻟﻨﺠﻢ ا ﺮﻛﺰي ورﻳﺎﺣﻪ ﺗﻘﺬف ﻫﺬه ا ـﻮاد أو أن اﻟﻐﺒﺎر ﻳﻨﻤـﻮ إﱃ أﺟﺴـ ﺎم أﻛـﱪ ﺘﺗو ﺸـﻜﻞ اﻟﻜﻮاﻛــﺐ ﰲ اﻟﻨﻬﺎﻳــﺔ وﺑﻤــﺎ أن اﻟﺪراﺳ ـﺎت ــــــ اﻟﻤ ﺎﻩ