Free Astronomy Magazine September-October 2022 ARABIC VERSION

tence of Planet X without, however, excluding it definitively. In fact, it is still possible to hypothesize different combinations of mass, albedo and orbital properties capable of placing a possible ninth planet (not tenth, because Pluto is still officially classi- fied as a dwarf planet) beyond the capabilities of observation among the campaigns conducted so far. The main intervening factors that limit the chance of a discovery are the small apparent magnitude of a body so far away from the Sun, as well as its very slow apparent motion among the stars. We are talking about shifts on the celestial vault on the order of one arc minute per year if the planet is about 800 AU away from the Sun; proportionally less for increasing distances. At this point, it is obvious that the best strategy for discovering Planet Nine (as it is widely known today) is by compar- ing infrared images of the same areas of the sky acquired several years apart from each other. This strategy is the basis of a recent study conducted by Chris Sedgwick and Stephen Serjeant (School of Physical Sciences, The Open University, Mil- ton Keynes, UK), published in the Monthly Notices of the Royal Astro- nomical Society . Sedgwick and Serjeant compared the databases of two major surveys of the whole sky in the far-infrared, separated by 23.4 years (taking mid- points of the survey periods in each case). The two surveys are those car- ried out by the Infrared Astronomi- cal Satellite (IRAS), operational from ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ٣٧ إﺿﺎﻓﻴﺔ ﻋﲆ وﺟﻮد اﻟﻜﻮﻛـﺐ أﻛـﺲ وﻟﻜـﻦ ﺑﺪون اﺳﺘﺒﻌﺎده ﻧﻬﺎﺋﻴًﺎ ، ﻻ ﻳﺰال ﻣﻦ ا ﻤﻜـﻦ اﻓﱰاض ﻣﺠﻤﻮﻋـﺎت ﻣﺨﺘﻠﻔـﺔ ﻣـﻦ اﻟﻜﺘﻠـﺔ واﻻﻧﻌﻜﺎﺳﻴﺔ واﻟﺨﺼﺎﺋﺺ ا ﺪارﻳﺔ اﻟﻘـﺎدرة ﻋﲆ وﺿﻊ ﻛﻮﻛﺐ ﺗﺎﺳـﻊ ﻣﺤﺘﻤـﻞ ) وﻟـﻴﺲ اﻟﻌﺎﴍ ، ﻷ ن ﺑﻠﻮﺗﻮ ﻻ ﻳﺰال ﻳُﺼـﻨﻒ رﺳـﻤﻴًﺎ ﻋﲆ أﻧﻪ ﻛﻮﻛﺐ ﻗﺰم ( ﺑﻤـﺎ ﻳﺘﺠـﺎوز ﻗـﺪرات ا ﺮاﻗﺒﺔ ﺑ اﻟﺤﻤﻼت اﻟﺘﻲ ﺗﻢ إﺟﺮاؤﻫﺎ ﺑﻌﻴﺪ . إن اﻟﻌﻮاﻣﻞ اﻟﺮﺋﻴﺴﻴﺔ ا ﺘﺪاﺧﻠﺔ اﻟﺘﻲ ﺗﺤﺪ ﻣﻦ ﻓﺮﺻﺔ اﻻﻛﺘﺸـﺎف ﻫـﻲ اﻟﺤﺠـﻢ اﻟﻈـﺎﻫﺮي اﻟﺼﻐ ﻟﺠﺴـﻢ ﺑﻌﻴـﺪ ﺟـﺪًا ﻋـﻦ اﻟﺸـﻤﺲ ﺑﺎﻹﺿﺎﻓﺔ إﱃ ﺣﺮﻛﺘﻪ اﻟﻈﺎﻫﺮﻳﺔ اﻟﺒﻄﻴﺌﺔ ﺟﺪًا ﺑ اﻟﻨﺠﻮم . ﻧﺤﻦ ﻧﺘﺤﺪث ﻋـﻦ اﻟﺘﺤـﻮﻻت ﰲ اﻟﻘﺒـﻮ اﻟﺴـﻤﺎوي ﺑﻤﻌـﺪل دﻗﻴﻘـﺔ ﻗﻮﺳـﻴﻪ واﺣﺪة ﰲ اﻟﺴﻨﺔ ﻓـ ، ﺈذا ﻛـﺎن اﻟﻜﻮﻛـﺐ ﻋـﲆ ﻣﺴﺎﻓﺔ ﺗﺒﻠﻎ ٨٠٠ وﺣﺪة ﻓﻠﻜﻴﺔ ﻣﻦ اﻟﺸﻤﺲ أﻗﻞ ﻧﺴﺒﻴًﺎ ﻟﺰﻳﺎدة ا ﺴﺎﻓﺎت . ﰲ ﻫﺬه ا ﺮﺣﻠـﺔ ﻣﻦ اﻟﻮاﺿﺢ أن أﻓﻀﻞ إﺳﱰاﺗﻴﺠﻴﺔ ﻻﻛﺘﺸﺎف اﻟﻜﻮﻛﺐ اﻟﺘﺎﺳﻊ ) ﻛﻤـﺎ ﻫـﻮ ﻣﻌـﺮوف ﻋـﲆ ﻧﻄﺎق واﺳﻊ اﻟﻴﻮم ( ﻫﻲ ﻣﻦ ﺧﻼل ﻣﻘﺎرﻧـﺔ ﺻﻮر اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ﻟﻨﻔﺲ ا ﻨـﺎﻃﻖ ﻣﻦ اﻟﺴﻤﺎء اﻟﺘﻲ ﺗﻢ اﻟﺤﺼـﻮل ﻋﻠﻴﻬـﺎ ﻋـﺪة ﺳﻨﻮات ﺑﻌﻴﺪًا ﻋـﻦ ﺑﻌﻀـﻬﺎ اﻟـﺒﻌﺾ ﻫـﺬه اﻹﺳﱰاﺗﻴﺠﻴﺔ ﻫﻲ أﺳـﺎس دراﺳـﺔ ﺣﺪﻳﺜـﺔ ـــــ أﺟﺮاﻫﺎ اﻟﺒﺎﺣﺜﺎن ﻛﺮﻳﺲﺳﻴﺪﺟﻮﻳﻚ وﺳﺘﻴﻔﻦ ) ﴎﺟﻴﻨﺖ ﻛﻠﻴﺔ اﻟﻌﻠﻮم اﻟﻔﻴﺰﻳﺎﺋﻴﺔ ، اﻟﺠﺎﻣﻌﺔ ا ﻔﺘﻮﺣﺔ ﻣﻴﻠﺘﻮن ﻛﻴﻨـﺰ ﺑﺎ ﻤﻠﻜـﺔ ا ﺘﺤـﺪة ( وﻧُﴩت ﰲ اﻹﺧﻄﺎرات اﻟﺸـﻬﺮﻳﺔ ﻟﻠﺠﻤﻌﻴـﺔ ا ﻠﻜﻴــﺔ اﻟﻔﻠﻜﻴ ـﺔ . ﻟﻘــﺪ ﻗ ـﺎرن اﻟﺒﺎﺣﺜــﺎن ﺳﻴﺪﺟﻮﻳﻚ و ﴎﺟﻴﻨﺖ ﺑ ﻗﻮاﻋﺪ اﻟﺒﻴﺎﻧـﺎت ﺴﺤ رﺋﻴﺴﻴ ﻟﻠﺴﻤﺎء اﺟﺮﻳﺎ ﺑﺎﻟﻜﺎﻣـﻞ ﰲ اﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤـﺮاء اﻟﺒﻌﻴـﺪة وﻗـﺪ ﻛـﺎن اﻟﻔﺎﺻﻞ ﺑﻴﻨﻬ ﻤ ﺎ ﻣـﺪة زﻣﻨﻴـﺔ ﺑﻠﻐـﺖ ﺣـﻮاﱄ ٢٣.٤ )ﺳﻨﺔ ﻣﻊ أﺧﺬ ﻧﻘﺎط ﻣﻨﺘﺼﻒ ﻓـﱰات ا ﺴﺢ ﰲ ﻛﻞ ﺣﺎﻟﺔ ( ا ﺴﺤﺎن أﺟﺮاﻫ ﺎ اﻟﻘﻤﺮ ﻤ اﻟﺼﻨﺎﻋﻲ اﻟﺬي ﻳﻌﻤﻞ ﺑﺎﻷﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ـ ﺳﺒﺘﻤ أﻛﺘﻮﺑﺮ 2022 ﻣﺪارات ﻟـ ٩٦ ﻣﻦ ١٠٩ ﻮ ﻜ ﺎت ﻌ ﺪة ﻣﻌﺮوﻓﺔ وأﺟﺴﺎم ﻣﺘﻄﺮﻓﺔ ﻋﺎﺑﺮة ﻟ ﻮﻛﺐ ﻧ ﺘﻮن ﻧﻘﻄﺔ أوﺟﻬﺎ ﺗﺰ ﺪ ﻋﻠﻰ ٢٠٠ وﺣﺪة ﻓﻠﻜ ﺔ، ﺗﻠﻚ اﻟﻤﺪارات ﻣﺄﺧﻮذة ﻣﻦ ﻗﺎﻋﺪة ﺑ ﺎﻧﺎت ﻣﺨﺘ ﻧﺎﺳﺎ اﻟﺪﻓﻊ اﻟﻨﻔﺎث ﻟﻸﺟﺴﺎم اﻟﺼﻐ ة ، ﺗﻢ اﺳﺘ ﻌﺎد اﻟ ﻮ ﻜ ﺎت اﻟـ ١٣ اﻟﻤﺘ ﻘ ﺔ ﻣﻦ ﻫﺬا اﻟﺮﺳﻢ اﻟﺒ ﺎﻧﻲ ، ﻷن ﻣـﺪاراﺗﻬﺎ ﻏـ ﻣﺆﻛـﺪة اﻟﻤـﺪارات اﻟـ ـ ﻤﺮاء ﻫﻲ أﺟﺴﺎم ﻣﺘﻄﺮﻓﺔ ﻋﺎﺑﺮة ﻟﻨ ﺘﻮن أن اﻟﻤﺪارات ا ، ﻓﻲﺣ ﻟﺰرﻗﺎء ﻫﻲ ﻟﻸﺟﺴﺎم اﻟﻤﺘﻄﺮﻓﺔ اﻟﻌﺎﺑﺮة ﻧ ﺘﻮن ﻣﺼﻄﻔﺔ ﻣﻊ اﻟ ﻮﻛﺐ اﻟﺘﺎﺳﻊ . اﻟﻤﺪارات اﻟﻮرد ﺔ ﻫﻲ اﻟﻤﺪارات اﻟﺜﻼﺛﺔ اﻟﻤﻌﺮوﻓﺔ ، ﺳ ﺪﻧﺎ ) 2012 VP113 ، ﻟ ﻼ ﻮﻫﻮﻧﻮا ( ، ﺑ ﻨﻤﺎ اﻟﻤﺪارات اﻟ ﻨ ﺔ ﻫﻲ أﺟﺴﺎم ، ﻣـﻊ ﻣﺴـﺎﻓﺎتﺣﻀـ ﺾ ﻗﻨﻄﻮرات و ﻮ ﻜ ﺎت داﻣﻮ ﻠـﻮد داﺧﻞ ﻣﺪارﻧ ﺘﻮن اﺻﻐﺮ ﻣﻦ ٢٩.٩ وﺣﺪ (. , ة ﻓﻠﻜ ﺔ ﻟﻠﻤﻘﺎرﺔ ﻈﻬﺮاﻟﻤﺪاراﻟﻤﻔ ض ﻟﻠ ﻮﻛﺐ اﻟﺘﺎﺳﻊ ﺎﻟﻠﻮن اﻷرﺟﻮاﻧﻲ . [Wikimedia Commons]