Free Astronomy Magazine September-October 2022 ARABIC VERSION

of the many possible combinations of a planet of 5-15 Earth masses, between 200 AU and 1000 AU from the Sun, with an or- bital period between 10,000 and 20,000 years. According to the two Caltech re- searchers, the most likely combination is that of a planet as large as Neptune with an orbit at an average distance from the Sun of about 700 AU. This distance cor- responds to the lower limit adopted by Sedgwick and Serjeant in their study, since for shorter distances a planet of that size would have al- ready been located based on the perturbations of the orbits of many TNOs. The two researchers also set the upper limit of the survey to around 8000 AU based on the sensi- tivity limits of the IRAS and AKARI detectors and the distance of the potential target, whose proper mo- tion, at greater distances, would be too small to be detectable. Surpris- ingly, the comparison between the databases of IRAS and AKARI high- lighted more than 500 possible can- didates, sources that mostly appeared to be at distances fewer than 1000 AU and to have masses similar to or smaller than that of Neptune, both values exactly in the expected range for Planet Nine. However, when the team manually examined the individual infrared sources, they found that none of them were convincing. Most were located in-or-near faint integrated flow nebulae, structures also known as “galactic cirrus clouds.” These are diffuse clouds of interstellar gas not easily detectable at visible wave- lengths, but relatively bright in the far-infrared. Nothing to do, there- fore, with nearby Neptunian-sized planets. Although the work of Sedg- wick and Serjeant did not produce the desired results, the idea of com- paring databases of surveys widely spaced over time appears to be the main road to follow in the search for Planet Nine. The only alternative is to calculate its position in the sky starting from the strange orbital concentrations of some TNOs. Cur- rently, the selection of TNOs is still too limited to follow this path.     ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ٣٩ )٥ - ١٥ ( ﻛﺘﻠــﺔ أرﺿــﻴﺔ وﻳﺒﻌﺪ ﻣﺴﺎﻓﺔ ﺗﱰاوح ﺑـ ) ٢٠٠ – ١٠٠٠ ( وﺣــــﺪة ﻓﻠﻜﻴﺔ ﻣـﻦ اﻟﺸـﻤ ﺲ ﻣـﻊ ﻓﱰة ﻣﺪارﻳـﺔ ﺗـﱰاوح ﻣـﺎ ) ﺑـ ١٠,٠٠٠ - ٢٠,٠٠٠ ( . ﺳﻨﺔ وﻓﻘﺎً ﻟﻠﺒـﺎﺣﺜ ﻣـﻦ ﻣﻌﻬ ـﺪ ﻛﺎﻟﻴﻔﻮرﻧﻴ ـﺎ ﻓ ـﺎن اﻟﱰﻛﻴﺒـﺔ اﻷﻛﺜـﺮ ﺗﺮﺟﻴﺤـﺎً ﻫﻲ ﺗﻠﻚ اﻟﺨﺎﺻﺔ ﺑﻜﻮﻛـﺐ ﺑﺤﺠﻢ ﻛﻮﻛﺐ ﻧﺒﺘـﻮن ﻣـﻊ ﻣـــﺪار ﻋـــﲆ ﻣﺴـــﺎﻓﺔ ﻣﻦ اﻟﺸﻤﺲ ﺗﺒﻠﻎ ٧٠٠ وﺣﺪة ﻓﻠﻜﻴﺔ ، ﺗﺘﻮاﻓﻖ ﻫ ﺬه ا ﺴﺎﻓﺔ ﻣﻊ اﻟﺤﺪ اﻷدﻧﻰ اﻟـﺬي اﻋﺘﻤـﺪه اﻟﺒﺎﺣﺜـــﺎن ﺳـــﻴﺪﺟﻮﻳﻚ و ﺳـــﺎرﺟﻨﻴﺖ ﰲ دراﺳﺘﻬﻤ ﺎ ﻣﻦ ذﻟـﻚ اﻟﺤـ ، ﻷﻧـﻪ ﺑﺎﻟﻨﺴـﺒﺔ ﻟﻠﻤﺴﺎﻓﺎت اﻷﻗﴫ ﻛﺎن ﻣﻦ ا ﻤﻜﻦ ﺑﺎﻟﻔﻌـﻞ ﺗﺤﺪﻳﺪ ﻣﻮﻗﻊ ﻛﻮﻛﺐ ﺑﻬﺬا اﻟﺤﺠﻢ ﺑﻨـﺎءً ﻋـﲆ اﺿﻄﺮاﺑﺎت ﻣـﺪارات اﻟﻌﺪﻳـﺪ ﻣـﻦ اﻷﺟﺴـﺎم اﻟﻌﺎﺑﺮة ﻟﻨﺒﺘﻮن . ﺣﺪد اﻟﺒﺎﺣﺜـﺎن أﻳﻀًـﺎ اﻟﺤـﺪ اﻷ ﻋﲆ ﻟﻠﻤﺴﺢ إﱃ ﺣﻮاﱄ ٨٠٠٠ وﺣﺪة ﻓﻠﻜﻴـﺔ اﺳــﺘﻨﺎدًا إﱃ ﺣــﺪود ﺣﺴﺎﺳــﻴﺔ ﻛﺎﺷــﻔﺎت إراس) أﻛﺎري )و ( ( وﻣﺴﺎﻓﺔ اﻟﺠﺴﻢ ا ﺤﺘﻤﻞ اﻟــﺬي ﺳــﺘﻜﻮن ﺣﺮﻛﺘــﻪ ا ﻨﺎﺳــﺒﺔ ، ﻋــﲆ ﻣﺴﺎﻓﺎت أﻛﱪ ، ﺻﻐ ة ﺟﺪًا ﺑﺤﻴﺚ ﻻ ﻳﻤﻜـﻦ اﻛﺘﺸﺎﻓﻬﺎ ﻣﻦ ا ﺜ ﻟﻠﺪﻫﺸﺔ أن ا ﻘﺎرﻧﺔ ﺑ ﻗﻮاﻋﺪ ﺑﻴﺎﻧـﺎت ﻫـﺬﻳﻦ اﻟﻘﻤـﺮﻳﻦ اﻟﺼـﻨﺎﻋ ، ﻴ أﺑﺮزت أﻛﺜﺮ ﻣﻦ ٥٠٠ ﺟﺴﻢ ﻣﺤﺘﻤﻞ ،وا ﺼﺎدر اﻟﺘﻲ ﻇﻬﺮت ﰲ اﻟﻐﺎﻟﺐ ﻋﲆ ﻣﺴﺎﻓﺎت ﺗﺒﻠﻎ أﻗـﻞ ﻣﻦ ١٠٠٠ وﺣﺪة ﻓﻠﻜﻴﺔ وﻟﺪﻳﻬﺎ ﻛﺘﻞ ﻣﻤﺎﺛﻠﺔ أو أﺻﻐﺮ ﻣﻦ ﻛﺘﻠﺔ ﻛﻮﻛﺐ ﻧﺒﺘﻮن، وﻛﻼ اﻟﻘﻴﻤﺘـ ﺑﺎﻟﻀﺒﻂ ﰲ اﻟﻨﻄﺎق ا ﺘﻮﻗﻊ ﻟﻠﻜﻮﻛـﺐ اﻟﺘﺎﺳـﻊ وﻣﻊ ذﻟـﻚ، ﻋﻨـﺪﻣﺎ ﻓﺤـﺺ اﻟﻔﺮﻳـﻖ ﻣﺼـﺎدر اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء اﻟﻔ ﺮدﻳﺔ وﺟـﺪوا أن أﻳـﺎ ﻣﻨﻬﺎ ﻟﻢ ﻳﻜﻦ ﻣﻘﻨﻌًﺎ، ﻓﻘﺪ ﻛﺎن ﻣﻌﻈﻤﻬﺎ ﻳﻘـﻊ داﺧﻞ أو ﺑﺎﻟﻘﺮب ﻣﻦ ﺳـﺪم اﻟﺘـﺪﻓﻖ ا ﺘﻜﺎﻣـﻞ اﻟﺨﺎﻓﺖ وﻫﻲ ﻣﻨـﺎﻃﻖ ﺗُﻌـﺮف أﻳﻀًـﺎ ﺑﺎﺳـﻢ " اﻟﺴـﺤﺐ ا ﺠﺮﻳــﺔ اﻟﺮﻗﻴﻘ ـﺔ ﻲﻫــو " ﻏﻴ ـﻮم اﻧﺘﺸﺎرﻳﺔ ﻣـﻦ اﻟﻐـﺎز ﺑـ اﻟﻨﺠـﻮم ﻻ ﻳﻤﻜـﻦ اﻛﺘﺸﺎﻓﻬﺎ ﺑﺴﻬﻮﻟﺔ ﻋﻨﺪ أﻃﻮال ا ﻮﺟﺎت ا ﺮﺋﻴﺔ ـــ ﻟﻜﻨﻬﺎ ﺗ ﻜﻮن ﺳﺎﻃﻌﺔ ﻧﺴﺒﻴًﺎ ﰲ اﻷﺷـﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء اﻟﺒﻌﻴﺪة ﻟﺬﻟﻚ ﻻﳾء ﻳﻤﻜﻦ اﻟﻘﻴﺎم ﺑـﻪ ﻣﻊ اﻟﻜﻮاﻛﺐ اﻟﺘﻲ ﻳﻘﱰب ﺣﺠﻤﻬﺎ ﻣـﻦ ﺣﺠـﻢ ﻧﺒﺘـﻮن ، ﻋـﲆ اﻟـﺮﻏﻢ ﻣـﻦ أن ﻋﻤـﻞ اﻟﺒـﺎﺣﺜ ﺳـﻴﺪﺟﻮﻳﻚ و ﺳـﺎرﺟﻨﻴﺖ ﻟـﻢ ﻳﻌـﻂ اﻟﻨﺘـﺎﺋﺞ ا ﺘﻮﻗﻌﺔ، إﻻ أن ﻓﻜﺮة ﻣﻘﺎرﻧﺔ ﻗﻮاﻋـﺪ ﺑﻴﺎﻧـﺎت ا ﺴﻮﺣﺎت ا ﺘﺒﺎﻋﺪة زﻣﻨﻴﺎً ﻳﺒﺪو أﻧﻬـﺎ اﻟﻄﺮﻳـﻖ ا ﺜﺎﻟﻴ اﻟﺘﻲ ﺔ ﻳﺠﺐ إﺗﺒﺎﻋﻬ ﺎ ﻟﻠﺒﺤﺚ ﻋﻦ اﻟﻜﻮﻛﺐ اﻟﺘﺎﺳﻊ اﻻﻓﱰاﴈ، وﻗﺪ ﻳﻜﻮن اﻟﺒـﺪﻳﻞ اﻟﻮﺣﻴـﺪ ﻫـﻮ ﺣﺴـﺎب ﻣﻮﻗﻌــﻪ ﰲ اﻟﺴـﻤﺎء ﺑـﺪءًا ﻣـﻦ اﻟﱰﻛﻴﺰات ا ﺪارﻳﺔ اﻟﻐﺮﻳﺒﺔ ا ﺮﺻـﻮدة ﻟـﺒﻌﺾ اﻷﺟﺴﺎم اﻟﻌﺎﺑﺮة ﻟﻨﺒﺘﻮن، وﻟﻜﻦ ﻳﻌﺘﻘﺪ ﺑﺄﻧﻪ ﰲ اﻟﻮﻗﺖ اﻟﺤﺎﱄ ﻻ ﻳﺰال ﺧﻴﺎر اﻷﺟﺴـﺎم اﻟﻌـﺎﺑﺮة ن ﻟﻨﺒﺘﻮ ﺿﻤﻦ ﻋﻤﻠﻴﺎت اﻟﺒﺤﺚ . ﺳﺒﺘﻤ أﻛﺘﻮﺑﺮ 2022 أﻣﺜﻠــــــﺔ ﻟﺼــــــﻮر ﻣــــــﻦ اﻷﻗﻤــــــﺎر اﻟﺼــــــــــــﻨﺎﻋ ﺔ ﺗﺸــــــــــــﻤﻞ اﻟــــــــــــ إراس) ( ـــﺎري )و أ ( ﺗُﻈﻬِـــﺮ " اﻟ ﻮﻛــــــــــــــــــــــــــــﺐ اﻟﺘﺎﺳـــــــــــــــــــــــــــــﻊ " اﻻﻓ اﺿـــﻲداﺧــــﻞ اﻟﺴــــﺤﺐ اﻟﺮﻗ ﻘــــــﺔ اﻟﻤﺠﺮ ــــــﺔ ، وا ﻟــــــ ﻣـــــــــﻦﺷـــــــــ ﮫ اﻟﻤﺆﻛـــــــــﺪ أﻧﻬـــــــــﺎ ﺳـــ ﺐ ﺗـــﺪﻓﻖ اﻷﺷـــﻌﺔ ﺗﺤـــﺖ ـــــــــــﺪة ا ﻤــــــــــﺮاء اﻟ ﻌ . ﺗﺸـــــــــــ اﻟــــــــــــﺪواﺋﺮ إﻟــــــــــــﻰ إﺣــــــــــــﺪاﺛ ﺎت اﻷﻫــﺪاف : أ ﻤــﺮ ﻟـــ إراس) ( اﻷزرق ﻟــــ ـ ــــﺎري ) أ ( ــــﻢ ﺣ اﻟﺪواﺋﺮﺗ ﻤ . [C. Sedgwick and S. Serjeant]