Free Astronomy Magazine September-October 2023 ARABIC VERSION

T his image, taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, shows the young planetary system PDS 70, located nearly 400 light- years away from Earth. The system features a star at its centre, around which the planet PDS 70 b (highlighted with a solid yellow circle) is orbiting. On the same orbit as PDS 70b, indicated by a solid yellow ellipse, as- tronomers have detected a cloud of debris (circled by a yellow dotted line) that could be the building blocks of a new planet or the rem- nants of one already formed. The ring-like struc- ture that dominates the image is a circumstellar disc of material, out of which planets are forming. There is in fact another planet in this system: PDS 70c, seen at 3 o’clock right next to the inner rim of the disc. [ALMA (ESO/NAOJ/NRAO) /Balsa- lobre-Ruza et al.] Does this exoplanet have a sibling sharing the same orbit? by ESO − Bárbara Ferreira sing the Atacama Large Mil- limeter/submillimeter Array (ALMA), astronomers have found the possible ‘sibling’ of a planet orbiting a distant star. The team has detected a cloud of debris that might be sharing this planet’s orbit and which, they believe, could be the building blocks of a new planet or the remnants of one al- ready formed. If confirmed, this dis- covery would be the strongest evi- dence yet that two exoplanets can share one orbit. “Two decades ago it was predicted in theory that pairs of planets of similar mass may share the same orbit around their star, the so-called Trojan or co-orbital planets. For the first time, we have found evidence in favour of that idea,” says Olga Balsalobre-Ruza, a student at the Centre for Astrobiology in Madrid, Spain who led the paper published in Astronomy & Astrophysics . Trojans, rocky bodies in the same orbit as a planet, are common in our own Solar System, the most famous example being the Trojan asteroids of Jupiter — more than 12,000 rocky bodies that are in the same orbit around the Sun as the gas giant. As- tronomers have predicted that Tro- jans, in particular Trojan planets, could also exist around a star other than our Sun, but evidence for them ﻫﻞ ﻟﻬﺬا اﻟ ﻮﻛﺐ اﻟﻨ ﻤﻲ ﮫ ﻘﺎﺳﻤ ﺷﻘﻴﻖ ﻧﻔﺲاﻟﻤﺪار؟ ﺗُﻈﻬــــــــﺮﻫــــــــﺬﻩ اﻟﺼـــــــــﻮرة أﺧـــــــــﺬت اﻟــــــــ ﺑﻮاﺳــــــــﻄﺔ ﻣﺼـــــــــﻔﻮﻓ ﺔ ﻣﺮﺻـــــــــﺪ أﺗ ﺎﻣـــــــــ ﺎ اﻟﻤﻠ ﻤــــــ ي ﺗ/ ﺤــــــﺖ اﻟﻤﻠ ﻤــــــ ي اﻟﻜﺒــــــ ) ﻣﺮﺻــــــﺪ أﻟﻤــــــﺎ ( واﻟـــــــﺬ ﻌــــــﺪ اﻟﻤﺮﺻـــــــﺪ اﻷور و ﺑــــــــــــﻲ اﻟـــــــــــــﺠﻨﻮﺑﻲ ﺷــــــــــــﺮ ﺎً ـــــــــــــﮫ ﻓ اﻟﺸـــﺎب ـــﻮﻛ اﻟﻨﻈـــﺎم اﻟ PDS 70 اﻟــﺬ ﻳ ﻌــﺪ ﺣــﻮاﻟﻲ 400 ﺳــﻨﺔ ﺿــﻮﺋ ﺔ ﻣﻦ اﻷرض . ـﻢ ﻓـﻲﻣﺮﻛـﺰﻩ ﺘﻤ اﻟﻨﻈﺎم ﺑﻮﺟﻮد ﻧ ـــﺪورﺣﻮﻟـــﮫ اﻟ ﻮﻛـــﺐ PDS 70 b اﻟﻤﻈﻠـــــﻞ ـــــﺪاﺋﺮة ﺻـــــﻔﺮاء وﻓـــــﻲ ﻧﻔــــــﺲ ﻣﺪاراﻟ ﻮﻛﺐ ُﺸﺎر إﻟ ﮫ واﻟﺬ ﻘﻄـﻊ ﻧــــﺎﻗﺺ اﺻـــــﻔﺮ اﻟﻠـــــﻮن اﻛﺘﺸـــــﻒﺳـــــﺤﺎ ﺔ ـ ﻣــــــﻦ اﻟـــــــ ) ﺤﻄﺎم ﻣﺤﺎﻃـــــــﺔ ﺑﺨـــــــﻂ أﺻـــــــﻔﺮ ﻣــــــــــــﻨﻘﻂ ( ــــــــــــﻮن اﻟﻠ ﻨـــــــــــــﺎت ﻤﻜــــــــــــﻦ أن ﺗ ـــــــــ ـــــــــﺪ، أو ﻘﺎ اﻷﺳﺎﺳـــــــــ ﺔ ﻟ ﻮﻛـــــــــﺐﺟﺪ ﺎ ﻮﻛﺐ ﻣﻮﺟﻮد ﺎﻟﻔﻌﻞ . ﺷـــ ﻠﺖ ـــﺔ اﻟﺸـــﺒﻴﻬﺔ ﺎﻟـــ اﻟ ﻨ ـ ﺤﻠﻘﺔ اﻟـــ ﺗﻬــ ﻤﻦ ﻋﻠــﻰ اﻟﺼـــﻮرة ــﺎرة ﻋـــﻦ ﻫــﻲﻋ ﻗـــــﺮصﻣﺤ ﻄــــــﻲﻣــــــﻦ اﻟﻤــــــﺎدة ﺗﺘﺸــــــ ﻞ ﻣﻨـــــــﮫ اﻟ ﻮاﻛـــــــﺐ . ﻳﻮﺟـــــــﺪ ﻓـــــــﻲ اﻟﻮاﻗـــــــﻊ ﻮﻛــﺐ آﺧــﺮﻓــﻲﻫــﺬا اﻟﻨﻈـﺎم و اﻟــﺬ ﺑﺠﻮار اﻟ ﻈﻬﺮ ـ ﺔﺤﺎﻓ اﻟﺪاﺧﻠ ﺔ ﻟﻠﻘﺮص . ــــ ـ، ﺑﺎﺳﺘ ﺨﺪا ﺔ ﻣﺼﻔﻮﻓ ﻣﺮﺻـﺪ أﺗﻜﺎﻣـﺎ ا ﻠﻴﻤ ــﱰي / ﺗﺤـــﺖ ا ﻠﻴﻤ ــﱰي اﻟﻜﺒـــ أ ـﺎ ) ( اﻛﺘﺸـﻒ ﻋﻠﻤـﺎء اﻟﻔﻠـﻚ " اﻟﺸـﻘﻴﻖ " ا ﺤﺘﻤﻞ ﻟﻜﻮﻛﺐ ﻳـﺪور ﺣـﻮل ﻧﺠـﻢ ﺑﻌﻴـﺪ . اﻛﺘﺸﻒ اﻟﻔﺮﻳﻖ ﺳﺤﺎﺑﺔ ﻣﻦ اﻟﺤﻄﺎم اﻟﺘﻲ ﻗﺪ ﺗﺸ ـﱰك ﰲ ﻣــﺪار ﻫــﺬا اﻟﻜﻮﻛــﺐ، واﻟﺘــﻲ ﻳﻌﺘﻘـﺪون أﻧﻬـﺎ ﻳﻤﻜـﻦ أن ﺗﻜـﻮن اﻟﻠﺒﻨـﺎت اﻷﺳﺎﺳﻴﺔ ﻟﻜﻮﻛﺐ ﺟﺪﻳـﺪ أو ﺑﻘﺎﻳـﺎ ﻛﻮﻛـﺐ : ﻘﻠﻢ ﺎر ﺮا ﻓ ﺮا اﻟﻤﺮﺻﺪ اﻷوروﺑﻲ ـاﻟ ﺠﻨﻮﺑﻲ ﺗﺸﻜﻞ ﺑﺎﻟﻔﻌﻞ وإذا ﺗﻢ ﺗﺄﻛﻴﺪ ﻫﺬا اﻻﻛﺘﺸﺎف ﻓﺴـﻴﻜﻮن أﻗـﻮى دﻟﻴـﻞ ﺣﺘـﻰ اﻵن ﻋـﲆ أن ﻛﻮﻛﺒ ﻧﺠﻤﻴ ﻳﻤﻜﻦ أن ﻳﺸﱰﻛﺎ ﰲ ﻣـﺪار . واﺣﺪ " ﻗﺒﻞ ﻋﻘﺪﻳﻦ ﻣﻦ اﻟـﺰﻣﻦ ﻛـﺎن ﻣـﻦ ا ﺘﻮﻗﻊ ﻧﻈﺮﻳًـﺎ أن اﻟﻜﻮاﻛـﺐ اﻟﺜﻨﺎﺋﻴـﺔ ذات اﻟﻜﺘﻠﺔ ا ﻤﺎﺛﻠﺔ ﻗ ﺪ ﺗﺸـﱰك ﰲ ﻧﻔـﺲ ا ـﺪار ﺣﻮل ﻧﺠﻤﻬﺎ ﻣﺎ ﻳﺴﻤﻰ ﺑﺎﻟﻜﻮاﻛﺐ اﻟ ﻄﺮوادة أو اﻟﻜﻮاﻛﺐ ذات ا ﺪارات ا ﺸـ ،ﱰﻛﺔ ﺗﻘـﻮل أوﻟﺠﺎ ﺑﺎﻟﺴﺎﻟﻮﺑﺮ روزا اﻟﻄﺎﻟﺒﺔ ﰲ ﻣﺮﻛﺰ ﻋﻠﻢ ا ﻷﺣﻴﺎء اﻟﻔﻠﻜﻲ ﰲ ﻣﺪرﻳـﺪ ﺑﺈﺳـﺒﺎﻧﻴﺎ واﻟﺘـﻲ ﻗﺎدت اﻟﺒﺤﺚ ا ﻨﺸﻮر ﰲ ﻣﺠﻠﺔ ﻋﻠـﻢ اﻟﻔﻠـﻚ ﻗﺎدت اﻟﺒﺤﺚ ا ﻨﺸﻮر ﰲ ﻣﺠﻠﺔ ﻋﻠـﻢ اﻟﻔﻠـﻚ واﻟﻔﻴﺰﻳﺎء اﻟﻔﻠﻜﻴﺔ " : ﻟﻘﺪ وﺟﺪﻧﺎ دﻟﻴﻼً ﻟﺼﺎﻟﺢ ﻫﺬه اﻟﻔﻜﺮة ﻷول ﻣﺮة ." اﻟ ﺗﻌﺪ ﻄﺮوادة وﻫﻲ أﺟﺴﺎم ﺻﺨﺮﻳﺔ ﺗﺪور ﰲ ﻧﻔﺲ ﻣﺪار اﻟﻜﻮﻛﺐ ﺷﺎﺋﻌﺔ ﰲ ﻧﻈﺎﻣﻨﺎ اﻟﺸ ﻤﴘـ وأﺷـﻬﺮ ﻣﺜـﺎل ﻋﲆ ذﻟﻚ ﻫـﻮ ﻛﻮﻳﻜﺒـﺎ ت ﻃـﺮوادة اﻟﺘﺎﺑﻌـﺔ ﻟﻜﻮﻛﺐ ا ﺸﱰي أﻛﺜـﺮ ﻣـﻦ 12000 ﺟﺴـﻢ ﺗﻮﺟﺪ ﺻﺨﺮي ﰲ ﻧﻔﺲ ا ﺪار ﺣﻮل اﻟﺸـﻤﺲ ﻣﺜﻞ اﻟﻌﻤﻼق اﻟﻐﺎزي . ﺗﻮﻗﻊ ﻋﻠﻤﺎء اﻟﻔﻠﻚ أن أﺟﺴﺎم ﻃﺮوادة وﺧﺎﺻﺔ ﻛﻮاﻛـﺐ ﻃـﺮوادة، ﻳﻤﻜﻦ أن ﺗﻮﺟﺪ أﻳﻀًﺎ ﺣﻮل ﻧﺠـﻢ آﺧـﺮ ﻏـ - ﺳﺒﺘﻤﺒﺮ ﺃﻛﺘﻮﺑﺮ 2 0 2 3 ﺎﺳﺘﺨﺪام [ALMA (ESO/NAOJ/NRAO) Balsa-lobre-Ruza et al]