北河三 - 维基百科,自由的百科全书
觀測資料 曆元 J2000.0 | |
---|---|
星座 | 雙子座 |
星官 | 北河 (井宿) |
赤經 | 07h 45m 18.94987s[1] |
赤緯 | +28° 01′ 34.3160″[1] |
視星等(V) | 1.14[2] |
特性 | |
演化阶段 | 巨星 |
光谱分类 | K0III[3] |
U−B 色指数 | +0.86[2] |
B−V 色指数 | +1.00[2] |
变星类型 | Suspected[4] |
天体测定 | |
徑向速度 (Rv) | +3.23[5] km/s |
自行 (μ) | 赤经:–626.55[1] mas/yr 赤纬:–45.80[1] mas/yr |
视差 (π) | 96.54 ± 0.27[1] mas |
距离 | 33.78 ± 0.09 ly (10.36 ± 0.03 pc) |
绝对星等 (MV) | ±0.02 +1.08[6] |
詳細資料 | |
質量 | ±0.09 1.91[7] M☉ |
半徑 | ±0.1 8.8[8] R☉ |
表面重力 (log g) | ±0.09 2.685[8] |
亮度 | 43[9] L☉ |
溫度 | ±95 4666[8] K |
金属量 [Fe/H] | –0.07 to +0.19[8] dex |
自轉 | 558 days[10] |
自轉速度 (v sin i) | 2.8[11] km/s |
年齡 | 724[12] Myr |
其他命名 | |
參考資料庫 | |
SIMBAD | 资料 |
ARICNS | 资料 |
北河三,即雙子座β星(β Geminorum,縮寫為β Gem),是一顆位於雙子座,距離太陽約34光年,已經演化呈現橙色色調的巨星。它是最接近太陽的巨星。
自1943年迄今,這顆恆星的光譜是其它分類的依據標準之一[14]。在2006年,發現它有一顆行星,被命名為北河三b(β Gem b),並已確認它的軌道[8]。
恆星性質
[编辑]依巴谷天文測量衛星[15][16]以視差測得它與太陽的距離大約是33.78光年(10.36秒差距) [1]。
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Sun_from_Pollux_%28star%29.jpg/220px-Sun_from_Pollux_%28star%29.jpg)
北河三的視星等為1.14等[17],在亮星表中,它比同星座的北河二(雙子座α)還要明亮。北河三和太陽相比,質量約為太陽的2倍[7],直徑約為太陽的9倍[8]。北河三原本是一顆A型主序星[18],但已經耗盡了核心的氫燃料,並演化成為光譜類型為K0III的巨星 [3]。這顆恆星外面殼層的有效溫度大約是 4666 K[8],位於K型恆星呈現橙色色調的範圍內 [19]。北河三的投影轉速是2.8 km•s−1[11]。除了氫和氦之外的其他元素豐度,也就是金屬的豐度,估計範圍從太陽的85%至155%不等,還沒有正確的數值[8][20](需要注意的是天文學家所說的金屬,是指氫和氦之外的所有其他元素)。
軌道上的倫琴衛星(ROSAT)探測到微弱的X射線輻射,這是北河三有低水準磁活動的證據。來自這顆恆星的X射線輻射大約是1027 erg s−1,大約與來自太陽的相等。已經證實北河三的表面磁場強度低於1高斯,這是在恆星上發現的最微弱磁場之一。磁場的存在表明,北河三曾經是一顆具有更強磁場的Ap星[18]。恆星的徑向速度有小振幅的變化,但不是光度學上的變化 [21]。
行星系統
[编辑]自1993年起,科學家就測量到徑向速度的振盪,因而懷疑北河三有行星環繞著[22]。在2006年6月16日證實並宣布它有一顆行星。計算出北河三b的質量至少是木星的2.3倍,環繞北河三的周期大約是590日[8]。
成員 (依恆星距離) | 质量 | 半長軸 (AU) | 轨道周期 (天) | 離心率 | 傾角 | 半径 |
---|---|---|---|---|---|---|
b | >2.30 ± 0.45 MJ | 1.64 ± 0.27 | 589.64 ± 0.81 | 0.02 ± 0.03 | — | — |
相關條目
[编辑]參考資料
[编辑]- 資料
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, doi:10.1051/0004-6361:20078357
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- ^ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 Hatzes, A. P.; et al, Confirmation of the planet hypothesis for the long-period radial velocity variations of β Geminorum, Astronomy and Astrophysics, 2006, 457: 335–341, Bibcode:2006A&A...457..335H, arXiv:astro-ph/0606517
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- ^ 11.0 11.1 Massarotti, Alessandro; et al, Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity, The Astronomical Journal, January 2008, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
- ^ Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke, Stellar parameters and elemental abundances of late-G giants, Publications of the Astronomical Society of Japan, August 2008, 60 (4): 781–802, Bibcode:2008PASJ...60..781T, arXiv:0805.2434
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- ^ Perryman, Michael, The Making of History's Greatest Star Map, Astronomers’ Universe (Heidelberg: Springer-Verlag), 2010, Bibcode:2010mhgs.book.....P, doi:10.1007/978-3-642-11602-5
- ^ Lee, T. A., Photometry of high-luminosity M-type stars, Astrophysical Journal, October 1970, 162: 217, Bibcode:1970ApJ...162..217L, doi:10.1086/150648
- ^ 18.0 18.1 Aurière, M.; et al, Discovery of a weak magnetic field in the photosphere of the single giant Pollux, Astronomy and Astrophysics, September 2009, 504 (1): 231–237, Bibcode:2009A&A...504..231A, arXiv:0907.1423
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- ^ The abundance is determined by taking the value of [Fe/H] in the table to the power of 10. Hence, 10−0.07 = 0.85 while 10+0.19 = 1.55.
- ^ Henry, Gregory W.; et al, Photometric Variability in a Sample of 187 G and K Giants, The Astrophysical Journal Supplement Series, September 2000, 130 (1): 201–225, Bibcode:2000ApJS..130..201H, doi:10.1086/317346.
- ^ A. P. Hatzes; et al. Long-period radial velocity variations in three K giants. The Astrophysical Journal. 1993, 413: 339–348. Bibcode:1993ApJ...413..339H. doi:10.1086/173002.
- 文獻
- Hatzes; et al. Long-period radial velocity variations in three K giants. The Astrophysical Journal. 1993, 413: 339–348 [2007-12-10]. (原始内容存档于2019-12-11).
- Hatzes; et al. Confirmation of the planet hypothesis for the long-period radial velocity variations of β Geminorum. Astronomy and Astrophysics. 2006, 457: 335–341 [2020-10-02]. (原始内容存档于2009-05-01).
- Reffert; et al. Precise Radial Velocities of Giant Stars. II. Pollux and Its Planetary Companion. The Astrophysical Journal. 2006, 652: 661–665.
外部連結
[编辑]- Extrasolar planet confirmed around β Geminorum
- Precise Radial Velocities of Giant Stars II. Pollux and its Planetary Companion(页面存档备份,存于互联网档案馆)
- Notes for star HD 62509. The Extrasolar Planets Encyclopaedia. [2008-06-24]. (原始内容存档于2008-06-01).
- Pollux. SolStation. [2005-11-21]. (原始内容存档于2012-02-18).
- Sabine Reffert; et al. Precise Radial Velocities of Giant Stars II. Pollux and its Planetary Companion. Astrophys. J. 2006-07-07, 652 (1): 661–665 [2014-03-30]. Bibcode:2006ApJ...652..661R. arXiv:astro-ph/0607136
. doi:10.1086/507516.
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