Free Astronomy Magazine January-February 2025 ARABIC VERSION

like other circumstellar disks we’ve looked at,” said Andras Gáspár ofthe University of Arizona, a mem- beroftheresearchteam.“TheVega diskissmooth,ridiculouslysmooth.” The big surprise to the researchteam is that there is no obvious ev- idence for one or more large plan- etsplowingthroughtheface-on disk like snow tractors. “It’s making us rethink the range and variety among exoplanet systems,” saidKate Su of the University of Ari- zona, lead author of the paper pre- senting the Webb findings. Webb seestheinfraredglowfromadisk of particles the size of sand swirling around the sizzling blue-white star that is 40 times brighter than our Sun. Hubble captures an outer halo of this disk, with particles no bigger than the consistency of smoke that are reflecting starlight. The distribution of dust in the Vega debris disk is layered because thepressure of starlight pushes out the smallergrainsfasterthanlargergrains. “Different types of physics willlocatedifferent-sizedparti- clesatdifferentlocations,” said Schuyler Wolff of the University of Arizonateam,leadauthorofthe paper presenting the Hubble find- ings. “Thefactthatwe’reseeing dustparticlesizessortedoutcan help us understand the underlying dynamics in circumstellar disks.” TheVegadiskdoeshaveasubtle gap,around60AU(astronomical units) from the star (twice the dis- tanceofNeptunefromtheSun), but otherwise is very smooth all the way in until it is lost in the glare of the star. This shows that there are noplanetsdownatleasttoNep- tune- masscirculatinginlargeor- bits, as in our solar system, say the researchers. “We’re seeing in detail how much variety there is among circumstellar disks, and how that variety is tied into the underlying planetary sys- tems.We’refindingalotoutabout the planetary systems – even when wecan’tseewhatmightbehidden planets,” addedSu. “There’sstilla lot of unknowns in the planet-for- mation process, and I think these new observations of Vega aregoing to help constrain models of planet formation.” Newly forming stars accrete mate- rialfromadiskofdustandgasthat is the flattened remnant of the cloudfromwhichtheyareforming. In the mid-1990s Hubble found disks around many newly forming stars.Thedisksarelikelysitesof ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 21 ﻜﺸﻒ ـﺐ اﻟﻔﻀـﺎﺋﻲﻋـﻦ ﺗﻠﺴ ﻮب ﺟ ﻤﺲو ــــﺎ ﺗــــﻮﻫﺞ اﻟﻐ راﻟــــﺪاﻓﺊﻓــــﻲ أد ﺴــــ ﺎﻟﻮ، ﻋﻠــــﻰ ﻌـــــﺪ 23 ـــــﺎرﻣﻴـــــﻞ ﻣﻠ . ﻤﺘـــــﺪ اﻟﻘـــــﺮص اﻟــــــ ـ ﺨﺎرﺟﻲ ) اﻟﻤﻤﺎﺛﻞ ﻟ ﺤـ ﺰام ﺎﻳ ﻓﻲ اﻟﻨﻈﺎم اﻟﺸﻤﺴـﻲ ( ﻣﻦ 7 إﻟﻰ 15 ﻠ ﺎرﻣﻴﻞ ﻣ . ﻤﺘﺪ اﻟﻘﺮصاﻟﺪاﺧﻠﻲ ـ ﻣـــﻦ اﻟــــ ــــﺔ ﻟﻠﻘــــﺮص اﻟــــ ﺤﺎﻓﺔ اﻟﺪاﺧﻠ ـ ﺨﺎرﺟﻲ إﻟــــﻰ ﻣﻦ اﻟﻨ ﻢ ﻘ أﺳﻔﻞ ﺣ . ﻻ ﻳﻮﺟﺪ اﻧﺨﻔـﺎض ﻓـــــــﻲﺳـــــــﻄﻮع ﺳـــــــﻄﺢ اﻟﻘـــــــﺮص اﻟـــــــﺪاﺧﻠﻲ ﻣـــــــﻦ ﺣــﻮاﻟﻲ 3.7 إﻟــﻰ 7.2 ـــﺎرﻣﻴــﻞ ﻣﻠ . اﻟ ﻘﻌــﺔ ﻓـــﻲ اﻟﻤﺮﻛﺰﺗﺮﺟﻊ إﻟﻰ ﻧﻘﺺ اﻟﺒ ﺎﻧﺎت . [NASA, ESA, CSA, STScI,S.Wolff (Univ rsityofArizona),K.Su (University of Arizona), A. Gáspár (University of Arizona)] - ﻳﻨﺎﻳﺮ ﻓﺒﺮﺍﻳﺮ 2 0 2 5 ﻗﺎل أﻧﺪراس ﺟﺎﺳﺒﺎر ﻣﻦ ﺟﺎﻣﻌـﺔ أرﻳﺰوﻧـﺎ وﻫﻮ ﻋﻀﻮ ﰲ ﻓﺮﻳﻖ اﻟﺒﺤﺚ " : ﻣﺜﻞ اﻷﻗﺮاص اﻟﻨﺠﻤﻴﺔ اﻷﺧﺮى اﻟﺘـﻲ ﻧﻈﺮﻧـﺎ إﻟﻴﻬـﺎ ﻓـﺈن ﻗﺮص اﻟﻨـﴪ اﻟﻮاﻗﻊ (ﺎﻐﻓﻴ) ﺑﺸـﻜﻞ ﻣﺜـ ﻟﻠﺴﺨﺮﻳ ﺔ وا ﻔﺎﺟﺄة اﻟﻜﱪى ﻟﻔﺮﻳﻖ اﻟ ﺒﺤـﺚ ﻫﻲ أﻧﻪ ﻻ ﻳﻮﺟﺪ دﻟﻴـﻞ واﺿـﺢ ﻋـﲆ وﺟـﻮد ﻛﻮﻛﺐ أو أﻛﺜﺮ ﻛﺒ اﻟﺤﺠﻢ ﻳﺸـﻖ ﻃﺮﻳﻘـﻪ ﻋﱪ اﻟﻘﺮص ا ﻮاﺟﻪ ﻟﻠﻮﺟـﻪ ﻣﺜـﻞ ﺟـﺮارات اﻟﺜﻠﺞ ) وﻗﺎﻟﺖ ( ﻛﻴﺖ ﺳﻮ ﻣﻦ ﺟﺎﻣﻌﺔ أرﻳﺰوﻧﺎ ا ﺆﻟﻔﺔ اﻟﺮﺋﻴﺴﻴﺔ ﻟﻠﻮرﻗﺔ اﻟﺘﻲ ﺗﻘـﺪم ﻧﺘـﺎﺋﺞ : " وﻳﺐ ﻫﺬا ﻳﺠﻌﻠﻨﺎ ﻧﻌﻴﺪ اﻟﺘﻔﻜ ﰲ اﻟﻨﻄـﺎق واﻟﺘﻨﻮع ﺑ أﻧﻈﻤـﺔ اﻟﻜﻮاﻛـﺐ اﻟﻨﺠﻤ ". ﻴـﺔ ﻳﺮى ﺗﻠﺴﻜﻮب وﻳﺐ ﺗـﻮﻫﺞ اﻷﺷـﻌﺔ ﺗﺤـﺖ ـــــ اﻟﺤﻤﺮاء ﻣﻦ ﻗﺮص ﺟﺴﻴﻤﺎت ﺑﺤﺠﻢ اﻟﺮﻣﺎل ﺗﺪور ﺣﻮل اﻟﻨﺠﻢ اﻷزرق اﻷﺑـﻴﺾ اﻟﺴـﺎﺧﻦ اﻟﺬي ﻫﻮ أﻛﺜﺮ ﺳﻄﻮﻋ ﺎً ﻣﻦ ﺷﻤﺴﻨﺎ ﺑﺄرﺑﻌ . ﻣﺮة ﻳﻠﺘﻘﻂ ﺗﻠﺴﻜﻮب ﻫﺎﺑﻞ ﻫﺎﻟﺔ ﺧﺎرﺟﻴـﺔ ﻟﻬﺬا اﻟﻘﺮص ﻣﻊ ﺟﺰﻳﺌﺎت ﻻ ﻳﺰﻳـﺪ ﺣﺠﻤﻬـﺎ ﻋـﻦ ﻗـﻮام اﻟـﺪﺧﺎن واﻟﺘـﻲ ﺗﻌﻜـﺲﺿـﻮء اﻟﻨﺠﻮم . إن ﺗﻮزﻳﻊ اﻟﻐﺒﺎر ﰲ ﻗـﺮصﺣﻄـﺎم اﻟﻨـﴪ اﻟﻮاﻗﻊ (ﺎﻐﻓﻴ) ﻣﺘﻌﺪد اﻟﻄﺒﻘـﺎت ﻷن ﺿﻐﻂ ﺿﻮء اﻟﻨﺠﻢ ﻳﺪﻓﻊ اﻟﺤﺒﻴﺒﺎت اﻷﺻـﻐﺮ ﺣﺠﻤــﺎً إﱃ اﻟﺨــﺎرج ﺑﺸــﻜﻞ أﴎع ﻣــﻦ اﻟﺤﺒﻴﺒﺎت اﻷﻛﱪ ﺣﺠﻤﺎً . ﻳﻘﻮل ﺳـ ﻜﻴﻠﺮ ووﻟـﻒ ﻣـﻦ ﻓﺮﻳـﻖ ﺟﺎﻣﻌـﺔ أرﻳﺰوﻧﺎ و ا ﺆﻟﻒ اﻟﺮﺋﻴﴘ ﻟﻠﻮرﻗﺔ اﻟﺘﻲ ﺗﻘـﺪم ﻧﺘﺎﺋﺞ ﻫﺎﺑﻞ " : ﺳﺘﺤﺪد أﻧـﻮاع ﻣﺨ ﺘﻠﻔـﺔ ﻣـﻦ اﻟﻔﻴﺰﻳﺎء اﻟﺠﺴﻴﻤﺎت ذات اﻷﺣﺠﺎم ا ﺨﺘﻠﻔﺔ ﰲ ﻣﻮاﻗﻊ ﻣﺨﺘﻠﻔـﺔ . إن ﺣﻘﻴﻘـﺔ أﻧﻨـﺎ ﻧـﺮى أﺣﺠﺎم ﺟﺰﻳﺌـﺎت اﻟﻐﺒـﺎر ﻣﺮﺗﺒـﺔ ﻳﻤﻜـﻦ أن ﺗﺴﺎﻋﺪﻧﺎ ﰲ ﻓﻬﻢ اﻟﺪﻳﻨﺎﻣﻴﻜﻴﺎت اﻷﺳ ﺎﺳﻴﺔ ﰲ اﻷﻗﺮاص ا ﺤﻴﻄﺔ ﺑﺎﻟﻨﺠﻮم . ﻳﺤﺘﻮي ﻗـﺮص اﻟﻨـﴪ اﻟﻮاﻗﻊ (ﺎﻐﻓﻴ) ﻋـﲆ ﻓﺠـﻮة ﻴﻘـﺔ رﻓ ﺣﻮاﱄ 60 وﺣﺪة ﻓﻠﻜ ﻴﺔ ﻣﻦ اﻟـﻨﺠﻢ ) ﺿـﻌﻒ ا ﺴﺎﻓﺔ ﺑ ﻧﺒﺘﻮن واﻟﺸﻤﺲ ( وﻟﻜﻦ ﺑﺨﻼف ذﻟﻚ ﻳﻜﻮن ﺳﻠﺴ ﺎً ﻟﻠﻐﺎﻳﺔ ﻃﻮال اﻟﻄﺮﻳﻖ ﺣﺘﻰ ﻳﻀﻴﻊ ﰲ وﻫﺞ اﻟﻨﺠﻢ . ﻳﻘﻮل اﻟﺒﺎﺣﺜﻮن ﻳ ﻈﻬـﺮ ﻫـﺬا أﻧـﻪ ﻻ ﺗﻮﺟـﺪ ﻛﻮاﻛﺐ ﻛﺘﻠﺘﻬﺎ ﺗﻌﺎدل ﻛﺘﻠﺔ ﻧﺒﺘـ ﻮن أو أﻛـﱪ ﺗﺪور ﰲ ﻣﺪارات ﻛﺒ ة ﻛﻤـﺎ ﻫـﻮ اﻟﺤـﺎل ﰲ ﻧﻈﺎﻣﻨﺎ اﻟﺸﻤﴘ . أﺿﺎف ﺳﻮ ": ﻧﺤـﻦ ﻧـﺮى ﺑﺎﻟﺘﻔﺼـﻴﻞ ﻣـﺪى اﻟﺘﻨـﻮع ا ﻮ ﺟـﻮد ﺑـ اﻷﻗـﺮاص ا ﺤﻴﻄـﺔ ﺑﺎﻟﻨﺠﻮم وﻛﻴﻒ ﻳﺮﺗﺒﻂ ﻫﺬا اﻟ ﺘﻨﻮع ﺑﺎﻷﻧﻈﻤﺔ اﻟﻜﻮﻛﺒﻴﺔ اﻷﺳﺎﺳﻴﺔ ﻧﺤﻦ ﻧﻜ و ﺘﺸﻒ اﻟﻜﺜـ ﻋـﻦ اﻷﻧﻈﻤـﺔ اﻟﻜﻮﻛﺒﻴـﺔ ﺣﺘـﻰ ﻋﻨـﺪﻣﺎ ﻻ ﻧﺴﺘﻄﻴﻊ أن ﻧﺮى ﻣﺎ ﻗﺪ ﻳﻜﻮن ﻛﻮاﻛﺐ ﺧﻔﻴﺔ و ﻻ ﻳﺰال ﻫﻨﺎك اﻟﻜﺜ ﻣﻦ ا ﺠﻬﻮل ﰲ ﻋﻤﻠﻴﺔ ﺗﻜﻮﻳﻦ اﻟﻜ ﻮاﻛﺐ وأﻋﺘﻘﺪ أن ﻫـﺬه اﻷ رﺻـﺎد اﻟﺠﺪﻳـﺪة ﻟ ـﻨﺠﻢ اﻟﻨ ــﴪ اﻟﻮاﻗ ـﻊ (ﺎﻐ ـ ﻓﻴ) ﺳﺘﺴﺎﻋﺪ ﰲ ﺗﻘﻴﻴﺪ ﻧﻤﺎذج ﺗﻜﻮﻳﻦ اﻟﻜﻮاﻛﺐ ." ﺗﱰاﻛﻢ اﻟﻨﺠﻮم اﻟﺘﻲ ﺗﺘﺸﻜﻞ ﺣﺪﻳﺜًﺎ ﻣﻮاد ﻣﻦ أﻗﺮاص اﻟﻐﺒﺎر واﻟﻐﺎز اﻟﺘﻲ ﺗﺘﺤﻮل إﱃ ﺑﻘﺎﻳـﺎ ﻣﺴﻄﺤﺔ ﻣﻦ ا ﻟﺴﺤﺎﺑﺔ اﻷﺻـﻠﻴﺔ وﻗـﺪ ﺟـﺪ ﻠﺗ ﺴـﻜﻮب ﻫﺎﺑـﻞ ﰲ ﻣ ﻨﺘﺼـﻒ اﻟﺘﺴـﻌﻴﻨﻴﺎت أﻗﺮاﺻ ﺎً ﺣﻮل اﻟﻌﺪﻳﺪ ﻣﻦ اﻟﻨﺠﻮم اﻟﺘﻲ ﺗﺘﺸﻜﻞ ﺣﺪﻳﺜًﺎ ﻣﻦ اﻟﻨﺠﻮم اﻟﺘﻲ ﺗﺘﺸﻜﻞ ﺣﺪﻳﺜًﺎ . ﻣـﻦ ا ﺤﺘﻤﻞ أن ﺗﻜﻮن اﻷﻗﺮاص ﻣﻮاﻗﻊ ﻟﻠﻬﺠﺮة،