This is an artist’s representation of a brown dwarf. This class of object is too large to be a planet (and did not form in the same way), but is too small to be a star because it cannot sustain nuclear fusion, since it is less massive than even the smallest stars. A brown dwarf is likely to be marked by wind-driven horizontal bands of thick clouds that may alternate with relatively cloud-free bands, giving the object a striped appearance. Whirling storm systems as big as terrestrial continents, or even small planets, might exist. The name ‘brown dwarf’ is actually a misnomer because the object would typically appear red to the naked eye. It is brightest in infrared light. Many brown dwarfs have binary companions. But as they age, the binary system drifts apart and each dwarf goes its separate way, according to a recent Hubble Space Telescope study. The background stars in this illustration are a science visualisation assembled from the Gaia spacecraft star catalogue. The synthesised stars are accurate in terms of position, brightness, and colour. Because this is not an image of the Milky Way, missing are glowing nebulae and dark dust clouds. [Image description: This artist’s representation shows a brown dwarf, an object more massive than a planet but smaller than a star. The dwarf is a cherry-red sphere. It has horizontal stripes of various shades of red that are cloud bands. In the dark background there are myriad stars that are inside our Milky Way galaxy.]
【新唐人北京時間2024年03月26日訊】美國國家航空航天局（NASA）在最近所進行的調查中發現，有些褐矮星（brown dwarf，或稱棕矮星 ）孤零零地在太空中獨自生存，沒有其它褐矮星相伴。這證明了原本成對的褐矮星可能隨著時間的推移而「分手」。
褐矮星是比木星還大的天體，但比質量最小的恆星還小，所以不能被歸類為恆星。但就像恆星一樣，褐矮星可能成對誕生，與另一顆褐矮星互相環繞軌道運行。
NASA藉由其哈勃太空望遠鏡（Hubble Space Telescope）所進行的調查發現，當褐矮星的年齡比較大時，它們比較不可能有其它褐矮星相伴。
這意味著由兩顆褐矮星組成的雙星系統，雙方之間的引力非常弱，以致於在鄰近恆星的吸引之下，它們在相處幾億年之後，就會分道揚鑣。
哈勃太空望遠鏡可以偵測到彼此距離只有4.8億公裡（相當於太陽與主小行星帶之間的距離）的雙星，但從事本次調查的天文學家在太陽系鄰近地區的一些褐矮星中沒有發現有任何伴星。
這項研究的主要報告撰寫人、加拿大蒙特婁大學（Université de Montréal）研究人員方塔尼夫（Clémence Fontanive）說：「我們的調查證實，在質量最小、溫度最低的單獨褐矮星中，有相距甚遠的伴星是非常罕見的，即便我們觀測到比較年輕的褐矮星雙星系統也是如此。這意味著這種系統無法隨時間存續下去。」
本次哈勃太空望遠鏡的發現可以進一步支持褐矮星的誕生方式與恆星相同的理論，也就是經由氫分子的重力塌縮而生成。但不同之處在於，褐矮星沒有足夠的質量維持氫的核融合（又稱核聚變）來產生能量，但恆星就有足夠的質量。
方塔尼夫表示，銀河系中超過一半的恆星都有伴星，它們是在恆星形成過程中產生的。比較巨大的恆星比較常在雙星系統中被發現。
她說，他們的調查所提供的直接證據顯示，他們觀測到的年輕褐矮星雙星系統不太可能存續到年老時，它們可能會分開。這是因為褐矮星非常輕，雙星系統中兩顆褐矮星之間的引力非常弱，附近的恆星很容易就把兩者拆散。
參與這項研究的英國愛丁堡大學（University of Edinburgh）研究人員比勒（Beth Biller）補充說：「大多數恆星都有朋友，無論那是雙星系統或系外行星。」
她說，這項調查確實證實，褐矮星的情況並非如此。褐矮星在生命的初期經歷一段有同伴的短暫時光之後，大多數都會在餘生中保持「單身」。
方塔尼夫說：「這是到目前為止，成對褐矮星隨時間分離的最佳觀測證據。如果沒有哈勃太空望遠鏡的敏銳觀測能力和靈敏度，我們無法完成這種調查。」
（轉自大紀元/責任編輯：葉萍）
![This is an artist’s representation of a brown dwarf. This class of object is too large to be a planet (and did not form in the same way), but is too small to be a star because it cannot sustain nuclear fusion, since it is less massive than even the smallest stars. A brown dwarf is likely to be marked by wind-driven horizontal bands of thick clouds that may alternate with relatively cloud-free bands, giving the object a striped appearance. Whirling storm systems as big as terrestrial continents, or even small planets, might exist. The name ‘brown dwarf’ is actually a misnomer because the object would typically appear red to the naked eye. It is brightest in infrared light. Many brown dwarfs have binary companions. But as they age, the binary system drifts apart and each dwarf goes its separate way, according to a recent Hubble Space Telescope study. The background stars in this illustration are a science visualisation assembled from the Gaia spacecraft star catalogue. The synthesised stars are accurate in terms of position, brightness, and colour. Because this is not an image of the Milky Way, missing are glowing nebulae and dark dust clouds. [Image description: This artist’s representation shows a brown dwarf, an object more massive than a planet but smaller than a star. The dwarf is a cherry-red sphere. It has horizontal stripes of various shades of red that are cloud bands. In the dark background there are myriad stars that are inside our Milky Way galaxy.]](https://i.ntdtv.com/assets/uploads/2024/03/id103865240-heic2405a.jpg)
