扶筐四
（重定向自HD 175306）
  | |
| 觀測資料 曆元 J2000 | |
|---|---|
| 星座 | 天龍座 |
| 星官 | 扶筐 （女宿） |
| 赤經 | 18h 51m 12.09530s[1] |
| 赤緯 | +59° 23′ 18.0627″[1] |
| 視星等（V） | 4.65[2] |
| 特性 | |
| 光谱分类 | G9III[3] |
| U−B 色指数 | +1.19[2] |
| 变星类型 | RS CVn + 食變星[4] |
| 天体测定 | |
| 徑向速度 (Rv) | −19.52[5] km/s |
| 自行 (μ) | 赤经：77.47[1] mas/yr 赤纬：25.37[1] mas/yr |
| 视差 (π) | 9.54 ± 0.21[1] mas |
| 距离 | 106.8[4] pc |
| 绝对星等 (MV) | −0.344[6] |
| 軌道[4] | |
| 繞行週期 (P) | 138.444 ± 0.003 days |
| 半長軸 (a) | 0.00651 ± 0.00003" |
| 偏心率 (e) | 0.158 ± 0.003 |
| 倾斜角 (i) | 89.6 ± 0.3° |
| 升交点黃經 (Ω) | 22.9 ± 0.2° |
| 近心点 曆元 (T) | 2454983.0 ± 0.2 |
| 近心點幅角 (ω) (secondary) | 293.0 ± 0.6° |
| 半振幅 (K1) (primary) | 23.42 ± 0.05 km/s |
| 半振幅 (K2) (secondary) | 32.0 ± 0.4 km/s |
| 詳細資料 | |
| ο Dra A | |
| 質量 | 1.35[4] M☉ |
| 半徑 | 25.1[4] R☉ |
| 表面重力 (log g) | 1.769[4] |
| 亮度 | 220[4] L☉ |
| 溫度 | 4400[7] K |
| 金属量 [Fe/H] | −0.5[3] dex |
| 自轉 | 79[4] |
| 自轉速度 (v sin i) | 20.0[6] km/s |
| 年齡 | 3.0[4] Gyr |
| ο Dra B | |
| 質量 | 0.99[4] M☉ |
| 半徑 | 1.0[4] R☉ |
| 表面重力 (log g) | 4.43[4] |
| 亮度 | 1.3[4] L☉ |
| 溫度 | 6,000[4] K |
| 其他命名 | |
| 參考資料庫 | |
| SIMBAD | 资料 |
扶筐四（Omicron Draconis，拉丁化為ο Draconis，縮寫為ο Dra）是星座天龍座的一顆巨星，距地球322.93光年。在北緯31o以北的地區，它是一顆拱極星，這意味著這顆恆星在夜空中永遠不會升起或落下。
這是一個單線光譜聯星系統[7]，但已使用干涉測量術檢測到伴星。它是帶有食的獵犬座RS型變星系統，變化的總幅度只有百分之幾星等[8][4]。伴星與太陽相似，大概是一顆主序星，而主星是一顆比太陽大25倍，亮度高出200倍的巨星。
極星的身份
[编辑]扶筐四是距離水星北天極最近的恆星，因此可以認為是水星的極星[9]。除此之外，這顆恆星每18.6年會成為月球的北極星一次[10]。這是因為月球自轉軸的進動，使其極星的狀態定期變化。
參考文獻
[编辑]- ^ 1.0 1.1 1.2 1.3 1.4 Van Leeuwen, F. Validation of the new Hipparcos reduction. Astronomy and Astrophysics. 2007, 474 (2): 653–664. Bibcode:2007A&A...474..653V. S2CID 18759600. arXiv:0708.1752
. doi:10.1051/0004-6361:20078357.
- ^ 2.0 2.1 Hoffleit, Dorrit; Jaschek, Carlos. The Bright star catalogue. New Haven. 1991. Bibcode:1991bsc..book.....H.
- ^ 3.0 3.1 Keenan, Philip C.; McNeil, Raymond C. The Perkins catalog of revised MK types for the cooler stars. Astrophysical Journal Supplement Series. 1989, 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
- ^ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 Roettenbacher, Rachael M.; Monnier, John D.; Fekel, Francis C.; Henry, Gregory W.; Korhonen, Heidi; Latham, David W.; Muterspaugh, Matthew W.; Williamson, Michael H.; Baron, Fabien; Ten Brummelaar, Theo A.; Che, Xiao; Harmon, Robert O.; Schaefer, Gail H.; Scott, Nicholas J.; Sturmann, Judit; Sturmann, Laszlo; Turner, Nils H. Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries. II. O Draconis, a Candidate for Recent Low-mass Companion Ingestion. The Astrophysical Journal. 2015, 809 (2): 159. Bibcode:2015ApJ...809..159R. S2CID 119228345. arXiv:1507.03601 . doi:10.1088/0004-637X/809/2/159.
- ^ Karataș, Yüksel; Bilir, Selçuk; Eker, Zeki; Demircan, Osman; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser, Adam J. Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution. Monthly Notices of the Royal Astronomical Society. 2004, 349 (3): 1069–1092. Bibcode:2004MNRAS.349.1069K. S2CID 15290475. arXiv:astro-ph/0404219 . doi:10.1111/j.1365-2966.2004.07588.x .
- ^ 6.0 6.1 Böhm-Vitense, Erika; et al. Ultraviolet Emission Lines in BA and Non-BA Giants. The Astrophysical Journal. December 2000, 545 (2): 992–999. Bibcode:2000ApJ...545..992B. doi:10.1086/317850 .
- ^ 7.0 7.1 Pourbaix, D.; Boffin, H. M. J. Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component. Astronomy and Astrophysics. February 2003, 398 (3): 1163–1177. Bibcode:2003A&A...398.1163P. S2CID 12361870. arXiv:astro-ph/0211483 . doi:10.1051/0004-6361:20021736.
- ^ omi Dra. The International Variable Star Index. AAVSO. [15 July 2022].
- ^ Sharrah, Paul C. Pole Stars of Other Planets (pdf). Arkansas Academy of Sciences Proceedings. 1975, XXIX: 62–63.
- ^ Patrick Moore. The Guinness Book of Astronomy Facts & Feats. 1983: 29.
In 1968 the north pole star of the Moon was Omega Draconis; by 1977 it was 36 Draconis. The south pole star is Delta Doradus.
