北河三
 北河三在双子座中的位置。 | |
| 观测资料 历元 J2000.0 | |
|---|---|
| 星座 | 双子座 |
| 星官 | 北河 (井宿) |
| 赤经 | 07h 45m 18.94987s[1] |
| 赤纬 | +28° 01′ 34.3160″[1] |
| 视星等（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 | |
| 径向速度 (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) | +1.08±0.02[6] |
| 详细资料 | |
| 质量 | 1.91±0.09[7] M☉ |
| 半径 | 8.8±0.1[8] R☉ |
| 表面重力 (log g) | 2.685±0.09[8] |
| 亮度 | 43[9] L☉ |
| 温度 | 4666±95[8] K |
| 金属量 [Fe/H] | –0.07 to +0.19[8] dex |
| 自转 | 558 days[10] |
| 自转速度 (v sin i) | 2.8[11] km/s |
| 年龄 | 724[12] Myr |
| 其他命名 | |
| 参考数据库 | |
| SIMBAD | 资料 |
| ARICNS | 资料 |
北河三，即双子座β星（β Geminorum，缩写为β Gem），是一颗位于双子座，距离太阳约34光年，已经演化呈现橙色色调的巨星。它是最接近太阳的巨星。
自1943年迄今，这颗恒星的光谱是其它分类的依据标准之一[14]。在2006年，发现它有一颗行星，被命名为北河三b（β Gem b），并已确认它的轨道[8]。
恒星性质
依巴谷天文测量卫星[15][16]以视差测得它与太阳的距离大约是33.78光年（10.36秒差距） [1]。
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北河三的视星等为1.14等[17]，在亮星表中，它比同星座的北河二（双子座α）还要明亮。北河三和太阳相比，质量约为太阳的2倍[7]，直径约为太阳的9倍[8]。北河三原本是一颗A型主序星[18]，但已经耗尽了核心的氢燃料，并演化成为光谱类型为K0III的巨星 [3]。这颗恒星外面壳层的有效温度大约是4666 K[8]，位于K型恒星呈现橙色色调的范围内 [19]。北河三的投影转速是2.8 km•s−1[11]。除了氢和氦之外的其他元素丰度，也就是金属的丰度，估计范围从太阳的85%至155%不等，还没有正确的数值[8][20]（需要注意的是天文学家所说的金属，是指氢和氦之外的所有其他元素）。
轨道上的伦琴卫星（ROSAT）探测到微弱的X射线辐射，这是北河三有低水准磁活动的证据。来自这颗恒星的X射线辐射大约是1027 erg s−1，大约与来自太阳的相等。已经证实北河三的表面磁场强度低于1高斯，这是在恒星上发现的最微弱磁场之一。磁场的存在表明，北河三曾经是一颗具有更强磁场的Ap星[18]。恒星的径向速度有小振幅的变化，但不是光度学上的变化 [21]。
行星系统
自1993年起，科学家就测量到径向速度的振荡，因而怀疑北河三有行星环绕着[22]。在2006年6月16日证实并宣布它有一颗行星。计算出北河三b的质量至少是木星的2.3倍，环绕北河三的周期大约是590日[8]。
| 成员 (依恒星距离) |
质量 | 半长轴 (AU) |
轨道周期 (天) |
离心率 | 倾角 | 半径 |
|---|---|---|---|---|---|---|
| b | >2.30 ± 0.45 MJ | 1.64 ± 0.27 | 589.64 ± 0.81 | 0.02 ± 0.03 | — | — |
相关条目
参考资料
- 资料
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, doi:10.1051/0004-6361:20078357
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- ^ Famaey, B.; et al, Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters, Astronomy and Astrophysics, January 2005, 430 (1): 165–186, Bibcode:2005A&A...430..165F, arXiv:astro-ph/0409579 , doi:10.1051/0004-6361:20041272
- ^ Carney, Bruce W.; et al, Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars, The Astronomical Journal, March 2008, 135 (3): 892–906, Bibcode:2008AJ....135..892C, arXiv:0711.4984 , doi:10.1088/0004-6256/135/3/892
- ^ 7.0 7.1 Hatzes, A. P.; et al, The mass of the planet-hosting giant star β Geminorum determined from its p-mode oscillation spectrum, Astronomy & Astrophysics, July 2012, 543: 9, Bibcode:2012A&A...543A..98H, arXiv:1205.5889 , doi:10.1051/0004-6361/201219332, A98.
- ^ 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 , doi:10.1051/0004-6361:20065445
- ^ Mallik, Sushma V., Lithium abundance and mass, Astronomy and Astrophysics, December 1999, 352: 495–507, Bibcode:1999A&A...352..495M
- ^ Koncewicz, R.; Jordan, C., OI line emission in cool stars: calculations using partial redistribution, Monthly Notices of the Royal Astronomical Society, January 2007, 374 (1): 220–231, Bibcode:2007MNRAS.374..220K, doi:10.1111/j.1365-2966.2006.11130.x
- ^ 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 , doi:10.1093/pasj/60.4.781
- ^ POLLUX -- Variable Star, SIMBAD (Centre de Données astronomiques de Strasbourg), [2012-01-14], （原始内容存档于2020-01-24）
- ^ Garrison, R. F., Anchor Points for the MK System of Spectral Classification, Bulletin of the American Astronomical Society, December 1993, 25: 1319 [2012-02-04], Bibcode:1993AAS...183.1710G, （原始内容存档于2019-06-25）
- ^ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; et al, The Hipparcos Catalogue, Astronomy and Astrophysics, July 1997, 323: L49–L52, Bibcode:1997A&A...323L..49P
- ^ 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 , doi:10.1051/0004-6361/200912050
- ^ The Colour of Stars, Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004 [2012-01-16], （原始内容存档于2012-03-10）
- ^ 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.
- 文献
- 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.
外部链接
- 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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