小熊座π1
小熊座π1[14]是在拱極星座小熊座北部的共同自行聯星[15]。該對的視星等分別為+6.58和+7.31，綜合星等為+6.1[2]。它們位於距離太陽約71光年的地方。兩星的角距離為31.4弧秒[15]，其對應於實際約680AU[16]，並以大約13,100年的週期互繞著彼此運行[9]。
| 觀測數據 曆元 J2000.0 分點 J2000.0 (ICRS) | |
|---|---|
| 星座 | 小熊座 |
| 小熊座 π1 A | |
| 赤經 | 15h 29m 11.18599s[1] |
| 赤緯 | +80° 26′ 54.9713″[1] |
| 視星等 (V) | +6.58[2] |
| 小熊座π1 B | |
| 赤經 | 15h 29m 23.59426s[1] |
| 赤緯 | +80° 27′ 00.9675″[1] |
| 視星等 (V) | +7.31[2] |
| 特性 | |
| 光譜分類 | G1.5 V(n)[3] + G9 V[4] |
| U−B 色指數 | +0.13[2] + +0.37[2] |
| B−V 色指數 | +0.67[2] + +0.79[2] |
| 天體測定 | |
| 小熊座π1 A | |
| 徑向速度 (Rv) | −16.27±0.09[5] km/s |
| 自行 (μ) | 赤經：−225.109[6] mas/yr 赤緯：+107.575[6] mas/yr |
| 視差 (π) | 45.8577 ± 0.0328[6] mas |
| 距離 | 71.12 ± 0.05 ly (21.81 ± 0.02 pc) |
| 絕對星等 (MV) | 4.94±0.04[7] |
| π1 UMi B | |
| 徑向速度 (Rv) | −15.40±0.70[5] km/s |
| 自行 (μ) | 赤經：−217.817[8] mas/yr 赤緯：+105.947[8] mas/yr |
| 視差 (π) | 45.8038 ± 0.0352[8] mas |
| 距離 | 71.21 ± 0.05 ly (21.83 ± 0.02 pc) |
| 詳細資料 | |
| 小熊座π1 A | |
| 質量 | 1.02[9] M☉ |
| 半徑 | 0.98[6] R☉ |
| 表面重力 (log g) | 4.40[10] |
| 亮度 | 0.929[6] L☉ |
| 溫度 | 5,771[10] K |
| 金屬量 [Fe/H] | −0.22[11] dex |
| 年齡 | 9.22±3.84[12] Gyr |
| π1 UMi B | |
| 質量 | 0.92[9] M☉ |
| 半徑 | 0.84[8] R☉ |
| 表面重力 (log g) | 4.50[10] |
| 亮度 | 0.520[8] L☉ |
| 溫度 | 5,408[10] K |
| 其他命名 | |
| 參考資料庫 | |
| SIMBAD | π1 UMi AB |
| π1 UMi A | |
| π1 UMi B | |
這兩顆恆星都是類太陽恆星，並已被列為天琴-武仙星協的可能成員，該星協是距離太陽最近的移動星群之一[16]，然而現在認為這不太可能[17]。 主星小熊座π1 A，質量比太陽高2%，表面有效溫度為5,771 K，半徑為太陽的的98%和輻射熱光度為太陽的93%。伴星，小熊座π1 B，質量是太陽的92%，溫度略低為5,408 K，半徑是太陽的 84%，光度略高於太陽的一半。
參考資料
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