Free Astronomy Magazine March-April 2024 ARABIC VERSION

A Signs of possible aurorae on isolated brown dwarf by NASA/ESA/CSA − Christine Pulliam stronomers using NASA’s James Webb Space Tele- scope have found a brown dwarf (an object more massive than Jupiter but smaller than a star) with infrared emission from methane, likely due to energy in its upper at- mosphere. This is an unexpected discovery because the brown dwarf, W1935, is cold and lacks a host star; therefore, there is no obvious source for the upper atmosphere energy. The team speculates that the methane emission may be due to processes generating aurorae. To help explain the mystery of the in- frared emission from methane, the team turned to our solar system. Methane in emission is a common feature in gas giants like Jupiter and Saturn. The upper-atmosphere heating that powers this emission is linked to aurorae. On Earth, aurorae are created when energetic particles blown into space from the Sun are captured by Earth’s magnetic field. They cascade down into our atmosphere along magnetic field lines near Earth’s poles, colliding with gas molecules and creating eerie, dancing curtains of light. Jupiter and Saturn have similar auroral processes that in- volve interacting with the solar wind, but they also get auroral con- tributions from nearby active moons like Io (for Jupiter) and Enceladus (for Saturn). For isolated brown dwarfs like W1935, the absence of a stellar wind to contribute to the au- roral process and explain the extra energy in the upper atmosphere re- quired for the methane emission is a mystery. The team surmises that either unac- counted internal processes like the atmospheric phenomena of Jupiter and Saturn, or external interactions with either interstellar plasma or a nearby active moon may help ac- count for the emission. The aurorae’s discovery played out like a detective story. A team led by Jackie Faherty, an astronomer at the American Museum of Natural His- tory in New York, was awarded time with the Webb telescope to investi- gate 12 cold brown dwarfs. Among those were W1935 – an object that was discovered by citizen scientist Dan Caselden, who worked with the Backyard Worlds Zooniverse project – and W2220, an object that was discovered using NASA’s Wide Field MARCH-APRIL 2024 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 22 ﻋﻼﻣﺎتﻣﺤﺘﻤﻠﺔ ﻟﻠﺸﻔﻖ اﻟﻘﻄ ﻋﻠﻰﻗﺰم ﻣﻌﺰول : ﻘﻠﻢ ﺑﻮﻟ ﺎم ﻛﺮﺴﺘ و ﺎﻟﺔ ﻧﺎﺳﺎ / و ﺎﻟﺔ اﻟﻔﻀﺎء اﻷوروﺑ ﺔ / و ﺎﻟﺔ اﻟﻔﻀﺎء اﻟﻜﻨﺪ ﺔ اﻛﺘﺸـﻒ ﻋﻠﻤﺎء ﻓﻠﻚ ﺑﺎﺳﺘﺨﺪام ﺗﻠﺴـﻜﻮب ﺟﻴ ﻤﺲ وﻳﺐ اﻟﻔﻀﺎﺋﻲ اﻟﺘﺎﺑﻊ ﻟﻨﺎﺳـﺎ ﻗﺰﻣـ ﺎً ) ﺎً ﺑﻨﻴ ﺟﺴﻢ أﻛﱪ ﻣﻦ ﻛﻮﻛﺐ ا ﺸﱰي وﻟﻜﻨـﻪ أﺻﻐﺮ ﻣﻦ ﻧﺠﻢ ﻣﻊ( اﻧﺒﻌﺎث ﻟ ﻸﺷﻌﺔ ﺗﺤـﺖ اﻟﺤﻤﺮاء ﻣﻦ ا ﻴﺜﺎن وﻣﻦ ا ﺤﺘﻤﻞ أن ﻳﻜـﻮن ذﻟـﻚ ﺑﺴـﺒﺐ اﻟﻄﺎﻗـﺔ ا ﻮﺟـﻮدة ﰲ ﻏﻼﻓـﻪ اﻟﺠﻮي اﻟﻌﻠﻮي . ﻫﺬا اﻛﺘﺸﺎف ﻏـ ﻣﺘﻮﻗـﻊ ﻷن اﻟﻘﺰم اﻟﺒﻨﻲ W1935 ﺑـﺎرد وﻳﻔﺘﻘـﺮ إﱃ ﻧﺠﻢ ﻣﻀﻴﻒ؛ وﻟﺬﻟﻚ ﻻ ﻳﻮﺟﺪ ﻣﺼﺪر واﺿﺢ ﻟﻠﻄﺎﻗﺔ ﰲ اﻟﻐﻼف اﻟﺠـﻮي اﻟﻌﻠـﻮي . ﻳﺘﻮﻗـﻊ اﻟﻔﺮﻳﻖ أن اﻧﺒﻌﺎث ا ﻴﺜﺎن ﻗﺪ ﻳﻜـﻮن ﺑﺴـﺒﺐ ﻋﻤﻠﻴﺎت ﺗﻮﻟﻴﺪ اﻟﺸﻔﻖ اﻟﻘﻄﺒﻲ . ﻟﻠﻤﺴـﺎﻋﺪة ﰲ ﺗﻔﺴ ﴎ اﻧﺒﻌﺎث ﻟ ﻸﺷﻌﺔ ﺗﺤﺖ اﻟﺤﻤﺮاء ﻣﻦ ا ﻴﺜﺎن، ﺛﻢ ﺗﺤـﻮل اﻟﻔﺮﻳـﻖ إﱃ ﻧﻈﺎﻣﻨـﺎ اﻟﺸﻤﴘ ﺣﻴﺚ ﻳﻌﺪ اﻧﺒ ﻌـﺎث ا ﻴﺜـﺎن ﺳـﻤﺔ ﺷﺎﺋﻌﺔ ﰲ اﻟﻜﻮاﻛﺐ اﻟﻐﺎزﻳﺔ ا ﻟﻌﻤﻼﻗـﺔ ﻣﺜـﻞ ﻛﻮﻛﺐ ا ﺸـﱰي وزﺣـﻞ ﻳـ . ﺮﺗﺒﻂ ﺗﺴـﺨ اﻟﻐﻼف اﻟﺠﻮي اﻟﻌﻠـﻮي اﻟـﺬي ﻳﻐـﺬي ﻫـﺬا اﻻﻧﺒﻌﺎث ﺑﺎﻟﺸﻔﻖ اﻟﻘﻄﺒﻲ . أﻣﺎ ﻋـﲆ اﻟﻜـﺮة اﻷرﺿـﻴﺔ ﻓﻴﻨﺸـﺄ اﻟﺸـﻔﻖ اﻟﻘﻄﺒﻲ ﻋﻨـﺪﻣﺎ ﻳـﺘﻢ اﻟﺘﻘـﺎط اﻟﺠﺴـﻴﻤﺎت اﻟﻨﺸﻄﺔ ا ﻨﺒﻌﺜﺔ ﻣﻦ اﻟﺸـﻤﺲ إﱃ اﻟﻔﻀـﺎء ﺑﻮاﺳﻄﺔ ا ﺠﺎل ا ﻐﻨﺎﻃﻴﴘ ﻟﻸرض . اﻧﻬﺎ ﺗﺘﺪﻓﻖ إﱃ اﻟﻐﻼف اﻟﺠﻮي ﻟـﻸرض ﻋـﲆ ﻃﻮل ﺧﻄﻮط ا ﺠﺎل ا ﻐﻨﺎﻃﻴ ـ ﴘ ﺑـﺎﻟﻘﺮب ﻣﻦ ﻗﻄﺒﻲ اﻷرض وﺗﺘﺼﺎدم ﻣـﻊ ﺟﺰﻳﺌـﺎت اﻟﻐــﺎز وﺗﺨﻠــﻖ ﺳــﺘﺎﺋﺮ ﺿــﻮﺋﻴﺔ ﻏﺮﻳﺒــﺔ . وراﻗﺼﺔ ﻳﻤﺘﻠﻚ ا ﺸـﱰي وزﺣـﻞ ﻋﻤﻠﻴـﺎت ﺷﻔﻘﻴﺔ ﻣﺘﺸـﺎﺑﻬﺔ ﺗﺘﻀـﻤﻦ اﻟﺘﻔﺎﻋـﻞ ﻣـﻊ اﻟﺮﻳﺎح اﻟﺸﻤﺴﻴﺔ ﻟﻜﻨﻬﻤﺎ ﻳﺤﺼﻼن أﻳﻀ ﺎً ﻋﲆ ﻣﺴﺎﻫﻤﺎت ﺷﻔﻘﻴﺔ ﻣـﻦ اﻷﻗﻤـﺎر اﻟﻨﺸـﻄﺔ اﻟﻘﺮﻳﺒـﺔ ﻣﺜــﻞ ) ا ﻳـﻮ أ ﺑﺎﻟﻨﺴـﺒﺔ ﻟﻠﻤﺸـﱰي ( وإﻧﺴﻴﻼدوس ) ﺑﺎﻟﻨﺴﺒﺔ ﻟﺰﺣـﻞ (. ﺑﺎﻟﻨﺴـﺒﺔ ﻟﻸﻗﺰام اﻟﺒﻨﻴﺔ ا ﻌﺰوﻟﺔ ﻣﺜـﻞ W1935 ، ﻓـﺈن ﻏﻴﺎب اﻟﺮﻳﺎح اﻟﻨﺠﻤﻴﺔ ﻟﻠﻤﺴﺎﻫﻤﺔ ﰲ اﻟﻌﻤﻠﻴﺔ اﻟﺸـﻔﻘﻴﺔ وﺗﻔﺴـ اﻟﻄﺎﻗــﺔ اﻹﺿــﺎﻓﻴﺔ ﰲ اﻟﻐﻼف اﻟﺠـﻮي اﻟﻌﻠـﻮي اﻟﻼزﻣـﺔ ﻻﻧ ﺒﻌـﺎث ا ﻴﺜﺎن ﻳﻌﺪ ﻟﻐﺰ .اً ﻳﻌﺘﻘﺪ اﻟﻔﺮﻳﻖ أن اﻟﻌﻤﻠﻴـﺎت اﻟﺪاﺧﻠﻴـﺔ ﻏـ ا ﺤﺴﻮﺑﺔ ﻣﺜﻞ اﻟ ﻈـﻮاﻫﺮ اﻟﺠﻮﻳـﺔ ﻟﻜﻮﻛـﺐ ا ﺸﱰي وزﺣﻞ أو اﻟﺘﻔﺎﻋﻼت اﻟﺨﺎرﺟﻴﺔ ﻣﻊ اﻟﺒﻼزﻣﺎ ﺑ اﻟﻨﺠﻮم أو ﻗﻤﺮ ﻧﺸﻂ ﻗﺮﻳﺐ ﻗﺪ ﺗﺴﺎﻋﺪ ﰲ ﺗﻔﺴ اﻻﻧﺒﻌﺎث . ﻛﺎن اﻛﺘﺸﺎف اﻟﺸﻔﻖ اﻟﻘﻄﺒﻲ ﺑﻤﺜﺎﺑﺔ ﻗﺼﺔ ﺑﻮﻟﻴﺴـﻴﺔ . ﺣﺼـﻞ ﻓﺮﻳـﻖ ﺑﻘﻴــ ﺎدة ﺟـﺎﻛﻲ ﻓﺎﻫﺮﺗﻲ ﻋﺎﻟﻢ اﻟﻔﻠﻚ ﰲ ا ﺘﺤﻒ اﻷﻣﺮﻳﻜﻲ ﻟﻠﺘﺎرﻳﺦ اﻟﻄﺒﻴﻌـﻲ ﰲ ﻧﻴﻮﻳـﻮرك ﻋـﲆ وﻗـﺖ ﺳﺘﺨﺪام ﻹ ﺗﻠﺴﻜﻮب وﻳﺐ ﻟﺪراﺳﺔ 12 ﻗﺰﻣـﺎً اُ ﺑﺎرد ﺎُ ﺑﻨﻴ وﻣﻦ ﺑ ﺗﻠﻚ اﻷﺟﺴﺎم W1935 - اﻟﺠﺴﻢ اﻟﺬي اﻛ ﺘﺸﻔﻪ ﻣﻮاﻃﻨـ ﻪ اﻟﻌـﺎﻟﻢ دان ﻛﺎﺳ ـﻴﻠﺪن و اﻟ ـﺬي ﻋﻤ ـﻞ ﻣــﻊ ﴩوع ـﻣ ـ " ﺑﺎﻛﻴﺎرد ورﻟﺪز زوﻧﻔ س و " W2220 ﻫـﻮ اﻟﺠﺴــﻢ اﻟ ـﺬي ﺗ ـﻢ اﻛﺘﺸـﺎﻓﻪ ﺑﺎﺳـﺘﺨﺪام ﻣﺴﺘﻜﺸﻒ ا ﺴﺢ ﺑﺎﻷﺷﻌﺔ ﺗﺤـﺖ اﻟﺤﻤـﺮاء واﺳﻊ اﻟﻨﻄﺎق اﻟﺘﺎﺑﻊ ﻟ ﻮﻛﺎﻟﺔ . ﻧﺎﺳﺎ رﺳـــــﻢ ﺗﺨ ﻠـــــﻲ ـــــ ﺼـــــﻮر اﻟﻘـــــﺰم اﻟ W1935 ، ﻘــــــﻊ ﻋﻠــــــﻰ ﻌــــــﺪ اﻟــــــﺬ ٤٧ ﺳــــــﻨﺔ ﺿــــــﻮﺋ ﺔ ﻣــــــﻦ اﻷرض . اﻛﺘﺸــــــــــﻒﻋﻠﻤــــــــــﺎء اﻟﻔﻠــــــــــﻚ ﺎﺳــــــــــﺘﺨﺪام ﺗﻠﺴ ﻮب ﺟ ﻤﺲ ـﺐ اﻟﻔﻀـﺎﺋﻲ اﻟﺘـﺎﺑﻊ ﻟ و ﻮ ﺎﻟـﺔ ﻧﺎﺳــــﺎ اﻧ ﻌــــﺎث اﻷﺷــــﻌﺔ ﺗﺤــــﺖ اﻟــــ ـ ﻤﺮاء ﻣــــﻦ ﻏــــﺎز اﻟﻤ ﺜـــﺎن اﻟﻘــــﺎدم ﻣـــﻦ W1935 وﻫــــﺬا اﻛﺘﺸــــﺎف ﻏــ ﻣﺘﻮﻗــﻊ ﻷن اﻟﻘــﺰم ــﺎرد و ﻔﺘﻘــﺮإﻟــﻰ ــ اﻟ ﻧ ﻢ ﻣﻀ ﻒ وﻟﺬﻟﻚ ﻓﺎﻧﮫ ﻻ ﻳﻮﺟﺪ ﻣﺼﺪرواﺿﺢ اﻟﻐــــــﻼف اﻟــــــ ﻟﻠﻄﺎﻗــــــﺔ ﻟﺘﺴــــــﺨ ـ ﺠﻮ ي اﻟﻌﻠــــــﻮي وﺟﻌﻞ ﻏﺎز اﻟﻤ ﺜﺎن ﺘﻮﻫﺞ . ﺘﻮﻗـــــﻊ اﻟﻔﺮ ـــــﻖ ـــــﻮن أن اﻧ ﻌـــــﺎث اﻟﻤ ﺜـــــﺎن ﻗـــــﺪ ﻳ ﻧ ﻤﺎ ﻫﻮ ﺘﻴﺠﺔ ﻟﻌﻤﻠ ﺎت ﺗﻮﻟ ﺪ اﻟﺸﻔﻖ اﻟﻘﻄ ﻣﻮﺿﺢ ﻓﻲ اﻟﺼﻮرة ﺎﻟﻠﻮن اﻷ ﻤﺮ . - ﻣﺎﺭﺱ ﺃﺑﺮﻳﻞ 2 0 2 4