Free Astronomy Magazine November-December 2023 ARABIC VERSION

A 46 ASTRO PUBLISHING The densest “Neptune” ever observed by IAC Outreach Team n international team of re- searchers, with participation from the Instituto de As- trofísica de Canarias, has discovered an extremely dense Neptune-sized planet, which challenges the con- ventional theories about the forma- tion and evolution of planets. It was first identified with NASA’s TESS satellite, and the present studies were made with the HARPS-N spec- trograph on the Telescopio Na- zionale Galileo (TNG), at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands). It is called TOI-1853b and is really peculiar: it orbits its star in only 30 hours, and although its radius is similar to that of Neptune (3.5 times that of the Earth) its mass is some four times bigger than expected for this size (73 times the mass of the Earth) which makes it the densest Neptunian exoplanet observed, with nearly twice the density of the Earth. TOI-1853b lies at a distance of 545 light years, towards the constella- tion Bootes, and is very close to its star, in a region normally classified as a “Neptune desert” in which there ought not to be any planets the size of Neptune, because of the intense radiation from the star. “If we rely on the theories of the for- mation and evolution of planets, we would not expect a planet to exist so close to its star,” comments Luca Naponiello, a doctoral student at the University of Rome, Tor Vergta, who is the first author of the paper. Its exact composition is not known. “It is a planet with a density too high to be a classical Neptunian type of planet, and we infer that it must be very rich in heavy ele- ments” adds Naponiello. The re- search team are looking at two possibilities. One of them is that TOI-1853b may be mainly rocky, sur- rounded by a thin gassy atmos- phere of hydrogen and helium. The other is that it might be composed partly of rock and partly of ice, so that given its high temperature, around 1200 degrees Celsius, this exoplanet might have an atmos- phere of water vapour. But the most challenging aspect for NOVEMBER-DECEMBER 2023 ﻧ ﺘﻮن " رﺻﺪ " اﻷﻛ ﻛﺜﺎﻓﺔ ﻋﻠﻰ اﻹ ﻃﻼق : ﻘﻠﻢ ﻓﺮﻖ اﻟﺘﻮﻋ ﺔ ﻣﻌﻬﺪ اﻟﻔ ﺎء اﻟﻔﻠﻜ ﺔ ﻓﻲﺟﺰر اﻟﻜﻨﺎري اﻛﺘﺘﺘﺘ ﻒﻬــ ﻓﺮﻳـــﻖ دوﱄ ﻣــﻦ اﻟﺒــﺎﺣﺜ ﺑﻤﺸﺎرﻛﺔ ﻣﻌﻬﺪ اﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴـﺔ ﰲ ﺟـﺰر اﻟﻜﻨﺎري ﺎً ﻛﻮﻛﺒ ﺷﺪﻳﺪ اﻟﻜﺜﺎﻓﺔ ﺑﺤﺠﻢ ﻧﺒﺘﻮن وﻫﻮ ﻣﺎ ﻳﺘﺤﺪى اﻟﻨﻈﺮﻳﺎت اﻟﺘﻘﻠﻴﺪﻳـﺔ ﺣـﻮل ﺗﻜﻮﻳﻦ وﺗﻄﻮر اﻟﻜﻮاﻛﺐ . ﺗﻢ اﻟﺘﻌﺮف ﻋﻠﻴﻪ ﻷول ﻣﺮة ﺑﺎﺳﺘﺨﺪام اﻟﻘﻤﺮ اﻟﺼﻨﺎﻋﻲ ﺗﻴﺴﺲ ) ( اﻟﺘﺎﺑﻊ ﻟ ﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ وﺗﻢ إﺟﺮاء ا ﻟﺪراﺳﺎت اﻟﺤﺎﻟﻴﺔ ﺑﺎﺳﺘﺨﺪام ﻣﻄﻴﺎف ) ( ان- ﻫــﺎرﺑﺲ ا ﻮﺟـﻮد ﻋـﲆ اﻟﺘﻠﺴـﻜﻮب اﻟﻮﻃﻨﻲ ﻏﺎﻟﻴﻠﻴﻮ ﰲ ﻣﺮﺻﺪ روﻛﻲ دي ﻟـﻮس ﻣﻮﺷﺎﺗﺸـﻮس ) ﻏﺎراﻓﻴــﺎ، ﻻ ﺑﺎ ــﺎ، ﺑ ﺠ ـﺰر اﻟﻜﻨﺎري .( ﻳُﻄﻠﻖ ﻋﲆ اﻟﻜﻮﻛﺐ اﺳﻢ TOI-1853b وﻫﻮ ﻏﺮﻳﺐ ﺑﺎﻟﻔﻌﻞ ﻓﻬﻮ ﻳﺪور ﺣﻮل ﻧﺠﻤﻪ ﺧﻼل 30 ﺳﺎﻋﺔ ﻓﻘﻂ وﻋﲆ اﻟﺮﻏﻢ ﻣﻦ أن ﻧﺼـﻒ ﻗﻄﺮه ﻣﺸـ ﺎﺑﻪ ﻟﻨﺼـﻒ ﻗﻄـﺮ ﻧﺒﺘـﻮن )3.5 أﺿﻌﺎف ﻧﺼﻒ ﻗﻄـﺮ اﻷرض ( إﻻ أن ﻛﺘﻠﺘـﻪ ــــ أﻛﱪ ﺑﺤﻮاﱄ أرﺑﻊ ﻣﺮات ﻣـﻦ ا ﺘﻮﻗـﻊ ﻟﻬـﺬا اﻟﺤﺠﻢ )73 ﻣﺮة ﻛﺘﻠﺔ اﻷرض ﻣﻤﺎ ( ﻳﺠﻌﻠـﻪ أﻛﺜﺮ اﻟﻜﻮاﻛﺐ اﻟﻨﺠﻤﻴـﺔ اﻟﺸـﺒﻴﻬﺔ ﺑﻜﻮﻛـﺐ ﻧﺒﺘﻮن ﻛﺜﺎﻓﺔ اﻟﺘﻲ ﺗﻢ رﺻـﺪﻫﺎ ﻠـﻎ ﺣﻴـﺚ ﺗﺒ ﻛﺜﺎﻓﺘﻪ ﺿﻌﻒ ﻛﺜﺎﻓﺔ اﻷرض ﺗﻘﺮﻳﺒ .ﺎً ﻳﺒﻌﺪ اﻟﻜﻮﻛـﺐ TOI-1853b ﻣﺴـﺎﻓﺔ ﺗﺒﻠـﻎ 545 ﺳﻨﺔ ﺿﻮﺋﻴﺔ ﺑﺎﺗﺠـﺎه ﻛﻮﻛﺒـﺔ اﻟﻌـﻮاء وﻫﻮ ﻗﺮﻳﺐ ﺟﺪ اً ﻣﻦ ﻧﺠﻤﻪ ﰲ ﻣﻨﻄﻘﺔ ﺗﺼﻨﻒ ﻋﺎدة ﻋـﲆ أﻧﻬـﺎ " ﺻـﺤﺮاء ﻧﺒﺘـﻮن " ﺣﻴـﺚ ﻳﻔـﱰضﻋـﺪم و ﺟـﻮد أي ﻛﻮاﻛـﺐ ﺑﺤﺠـﻢ ﻛﻮﻛـﺐ ﻧﺒﺘـﻮن ﺑﺴـﺒﺐ اﻹﺷــﻌﺎع اﻟﺸـﺪﻳﺪ اﻟﺼﺎدر ﻋﻦ اﻟﻨﺠﻢ . " إذا اﻋﺘﻤﺪﻧﺎ ﻋﲆ ﻧﻈﺮﻳﺎت ﺗﻜـﻮﻳﻦ وﺗﻄـﻮر اﻟﻜﻮاﻛﺐ ﻓﻠﻦ ﻧﺘﻮﻗﻊ وﺟـﻮد ﻛﻮﻛـﺐ ﻗﺮﻳـﺐ اً ﺟﺪ ﻣﻦ ﻧﺠﻤﻪ " ﻳﻌﻠﻖ ﻟﻮﻛﺎ ﻧﺎﺑﻮﻧﻴﻴﻠﻮ ﻃﺎﻟﺐ اﻟﺪ ﺑ ﻛﺘﻮراه ﺠﺎﻣﻌﺔ روﻣﺎ ﺗﻮرﻓ ﺟﺘﺎ ا ﺆﻟﻒ و اﻷول ﻟ ﻠﻮرﻗﺔ إن :" ﺗﺮﻛﻴﺒﺘﻪ اﻟﺪﻗﻴﻘـﺔ ﻏـ ا ﯨﻼل . ﻣﻌﺮوﻓﺔ ﻳﻀﻴﻒ ﻧﺎﺑﻮﻧﻴﻠﻮ " : إﻧﻪ ﻛﻮﻛـﺐ ذو ﻛﺜﺎﻓﺔ ﻋﺎﻟﻴﺔ ﺟﺪًا ﺑﺤﻴﺚ ﻻ ﻳﻤﻜـﻦ اﻋﺘﺒـﺎره ﻧﻮﻋًﺎ ﺎً ﻼﺳﻴﻜﻴ ﻛ ﻣﻦ اﻟﻜﻮاﻛـﺐ اﻟﺸـﺒﻴﻬﺔ ﺑﻜﻮﻛـﺐ ﻧﺒﺘﻮن وﻧﺤﻦ ﻧﺴ ﺘﻨﺘﺞ أﻧـﻪ ﻳﺠـﺐ أن ﻳﻜـﻮن اً ﺟﺪ ﺎً ﻏﻨﻴ ﺑﺎﻟﻌﻨﺎﴏ اﻟﺜﻘﻴﻠﺔ ." ﻳﻨﻈﺮ ﻓﺮﻳﻖ اﻟﺒﺤـﺚ ﰲ اﺣﺘﻤـﺎﻟ رﺋﻴﺴـﻴ أﺣﺪﻫ أن ﺎﻤ اﻟﻜﻮﻛﺐ TOI-1853b ﻗﺪ ﻳﻜﻮن ﺻﺨﺮﻳﺎً ﺑﺸـﻜﻞ أﺳـﺎﳼ وﻣﺤﺎﻃـ ﺎً ﺑﻐـﻼف ﺟــﻮي ﻏــﺎزي رﻗﻴــﻖ ﻣــﻦ اﻟﻬﻴــﺪروﺟ واﻟﻬﻴﻠﻴﻮم . اﻻﺣﺘﻤﺎل اﻵﺧﺮ ﻫـﻮ أن ﻫـﺬا اﻟﻜﻮﻛـﺐ ﻗـﺪ ﻳﺘﻜﻮن ﺟﺰﺋﻴ ﺎً ﻣـﻦ اﻟﺼـﺨﻮر وﺟﺰﺋﻴـ ﺎً ﻣـﻦ اﻟﺠﻠﻴﺪ ﻟﺬﻟﻚ ﻧﻈﺮًا ﻟﺪرﺟﺔ ﺣﺮ ارﺗـﻪ ا ﺮﺗﻔﻌـﺔ اﻟﺘﻲ ﺗﺒﻠﻎ ﺣﻮاﱄ 1200 درﺟﺔ ﻣﺌﻮﻳـﺔ ﻘـﺪ ﻓ ﻳﻜﻮن ﻟﻬﺬا اﻟﻜﻮﻛﺐ اﻟ ﻨﺠﻤـﻲ ﻏـﻼف ﺟـﻮي ﻳﺘﻜﻮن ﻣﻦ ﺑﺨﺎر ا ﺎء . ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 46 ﻧﻮﻓﻤﺒﺮ - ﺩﻳﺴﻤﺒﺮ 2 0 2 3 اﻛﺘﺸﻒ