天門二

天門二（室女座69，69 Virginis）是室女座的一颗^[10]恒星，距离地球约259光年。它可以用肉眼看见，是微弱的橙色恒星，视星等 4.76，^[2]但它疑似是变星，视星等从4.75到4.79之间变化。^[11]天门二以 -13 km/s 的日心径向速度向地球靠近。^[5]由于宇宙尘埃，天门二发出的光受到偏振。^[12]

69 Virginis

觀測資料 曆元 J2000.0
星座	室女座
星官	天门 （角宿）
赤經	13h 27m 27.16348s[1]
赤緯	−15° 58′ 24.8980″[1]
視星等（V）	4.76[2]
特性
演化阶段	水平分支
光谱分类	K0 III-IIIb CN1.5 CH0.5[3]
U−B 色指数	+1.06[4]
B−V 色指数	+1.09[4]
天体测定
徑向速度 (Rv)	2998871000000000000♠−12.9±0.5[5] km/s
自行 (μ)	赤经：−121.016[1] mas/yr 赤纬：+21.197[1] mas/yr
视差 (π)	12.5871 ± 0.2367[1] mas
距离	259 ± 5 ly (79 ± 1 pc)
绝对星等 (MV)	0.09[2]
詳細資料 [6]
質量	7000351000000000000♠3.51±0.94 M☉
半徑	15[7] R☉
表面重力 (log g)	7000270000000000000♠2.70±0.11
亮度	87.1[7] L☉
溫度	7003490900000000000♠4,909±92 K
金属量 [Fe/H]	0.11[8] dex
自轉速度 (v sin i)	4.3[7] km/s
年齡	7002288000000000000♠288+343 −156 Myr
其他命名
16 Vir、​NSV 6253、​BD+04°2604、​GJ 9444、​HD 116976、​HIP 65639、​HR 5068、​SAO 157946[9]
參考資料庫
SIMBAD	资料

天门二是演化了的K型巨星，恒星分类为K0 III-IIIb CN1.5 CH0.5，^[3]显示其恒星光谱中有过多的CN和CH分子。它是一个紅群聚巨星，表明它在水平分支的核心通过氦聚变产生能量。^[13]天门二的年龄约2.88亿年，质量是太阳的3.5倍^[6]，半径是太阳的15倍^[7]。它从扩大的光球辐射出的光是太阳的87倍^[7]，有效温度 4,909 K。^[6]

参考资料

1. Brown, A. G. A.; Vallenari, A.; Prusti, T.; de Bruijne, J. H. J.; et al. Gaia Data Release 2. Summary of the contents and survey properties. Astronomy & Astrophysics. 2018. Bibcode:2018A&A...616A...1G. arXiv:1804.09365 . doi:10.1051/0004-6361/201833051. VizieR中此天体在盖亚望远镜第二批数据发布的记录
2. Anderson, E.; Francis, Ch., XHIP: An extended hipparcos compilation, Astronomy Letters, 2012, 38 (5): 331, Bibcode:2012AstL...38..331A, S2CID 119257644, arXiv:1108.4971 , doi:10.1134/S1063773712050015.
3. 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. Hoffleit, Dorrit; Jaschek, Carlos, The Bright star catalogue, New Haven, 1991, Bibcode:1991bsc..book.....H
5. de Bruijne, J. H. J.; Eilers, A.-C., Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project, Astronomy & Astrophysics, October 2012, 546: 14, Bibcode:2012A&A...546A..61D, S2CID 59451347, arXiv:1208.3048 , doi:10.1051/0004-6361/201219219, A61.
6. Feuillet, Diane K.; et al, Determining Ages of APOGEE Giants with Known Distances, The Astrophysical Journal, 2016, 817 (1): 40, Bibcode:2016ApJ...817...40F, S2CID 118675933, arXiv:1511.04088 , doi:10.3847/0004-637x/817/1/40.
7. 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.
8. Meléndez, J.; et al, Chemical similarities between Galactic bulge and local thick disk red giant stars, Astronomy and Astrophysics, June 2008, 484 (3): L21–L25, Bibcode:2008A&A...484L..21M, S2CID 3201679, arXiv:0804.4124 , doi:10.1051/0004-6361:200809398.
9. 69 Vir. SIMBAD. 斯特拉斯堡天文資料中心.
10. Eggleton, P. P.; Tokovinin, A. A., A catalogue of multiplicity among bright stellar systems, Monthly Notices of the Royal Astronomical Society, September 2008, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, S2CID 14878976, arXiv:0806.2878 , doi:10.1111/j.1365-2966.2008.13596.x.
11. Samus, N. N.; et al, General Catalogue of Variable Stars, Astronomy Reports, 5.1, 2017, 61 (1): 80–88, Bibcode:2017ARep...61...80S, S2CID 125853869, doi:10.1134/s1063772917010085.
12. Leroy, J. L., A Polarimetric Investigation on Interstellar Dust Within 50-PARSECS from the Sun, Astronomy and Astrophysics, July 1993, 274 (1): 203, Bibcode:1993A&A...274..203L.
13. Alves, David R., K-Band Calibration of the Red Clump Luminosity, The Astrophysical Journal, August 2000, 539 (2): 732–741, Bibcode:2000ApJ...539..732A, S2CID 16673121, arXiv:astro-ph/0003329 , doi:10.1086/309278.