太陽與紅矮星、棕矮星、木星之間的比較。
這是一份有關最小質量恆星的列表 ,依木星 質量 與太陽質量 的多寡來依序排列。
恆星 質量是恆星最重要的一個要素。質量加上化學 成分能確定一顆恆星的光度 、實際上的大小和最後的命運。列在表上的恆星 質量都小於1倍太陽質量 ,包括棕矮星 與紅矮星 。研究顯示大於13倍木星質量的天體會發生氘 核聚變 ,而大於65倍木星質量的天體會產生鋰 聚變 ,因此恆星的質量不會低於13倍木星質量[ 1] 。棕矮星 是類恆星天體的一種,它們是所謂「失敗的恆星」(Failed Star),由於質量不足,不能像正常恆星那樣通過氫 核聚變維持光度,無法成為主序星 。但它們的內部及表面均呈對流狀態,不同的化學物質並不會在內部分層存在。研究表明褐矮星為處於13倍木星質量與75-80倍木星質量之間的天體。[ 2]
小質量恆星的種類
紅矮星(左)與太陽(右)的大小。
黑矮星
黑矮星 (Black dwarf )是一顆白矮星在溫度低到不再能發出可以被偵測到的光或熱時的狀態。因為目前宇宙還沒有觀測到黑矮星存在,因此其質量不明。[ 3]
棕矮星
棕矮星 (Brown dwarf )是一種小質量恆星。它們就是「失敗的恆星」。由於質量不足,不能像其他恆星通過氫核聚變維持光度,因此無法成為主序星,並導致其質量較低。棕矮星的質量為13倍至80倍木星質量,即太陽質量的0.01至0.08倍。[ 2]
紅矮星
紅矮星 (Red dwarf )是一種質量較小、溫度較低的恆星[ 1] ,其質量是太陽質量的0.075至0.5倍。[ 4]
橙矮星
橙矮星 (Orange dwarf ),是較為接近太陽質量的恆星種類,其質量是太陽質量的0.5至0.8倍。[ 5]
黃矮星
黃矮星 (Yellow dwarf ),是最接近太陽質量的恆星種類。這些恆星的質量大約在0.8至1.0太陽質量[ 5] 。太陽 也是一個黃矮星。[ 6]
白矮星
白矮星 (White dwarf ),是低質量恆星演化階段的最終產物。這些恆星的質量大於1太陽質量。[ 7]
列表
太陽(左上)、低質量的恆星(左中)、棕矮星(右中)、木星(右下)
棕矮星(左)與土星(右)的比較
OGLE-TR-122(中)與八大行星的比較
格利泽229 A與B的照片,該系統距離地球約19光年 。
2M1207 與2M1207b的照片,該系統距離地球約173光年 。
堰蜓座110913-773444
蝘蜓座110913-773444 比之前所知最小的棕矮星OTS 44 還要小,質量祇有8倍木星質量,甚至比一些太陽系外行星 還小。科學家對這個天體的分類還沒有取得共識,所以堰蜓座110913-773444可能是一顆次棕矮星 或是一顆流浪行星 。[ 9]
參見
參考
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