半人馬座ξ2

关于拜耳命名法的其它恆星系統，请见「半人馬座Xi1」。

半人馬座Xi² （ξ² Cen, ξ² Centauri）是在南天半人馬座的三星系統^[12]，這較寬的光學雙星視星等為裸眼可見的+4.30等^[2]，略比半人馬座ξ1A型主序星暗^[13]（+4.83等^[14]），年週視差6.98mas，距離太陽大約470光年。在這樣的距離，恆星會因為中間的星際塵埃造成消光，而使視星等減弱0.32等^[15]

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This system was discovered to be a single-lined spectroscopic binary in 1910 by American astronomer Joseph Haines Moore.^[16][17] The pair, component A, orbit each other with a period of 7.6497 days and an eccentricity of 0.35.^[8] The primary is a B-type star with a stellar classification of B1.5 V^[4] or B2 IV,^[5] depending on the source. This indicates it may be a main sequence star or a more evolved subgiant star. It has about 8.1^[4] times the mass of the Sun and radiates 1,702 times the solar luminosity from its outer atmosphere at an effective temperature of 20,790 K.^[9] It is a hybrid pulsator and shows spacings in both g and p modes.^[18]

A third star, component B, is a magnitude 9.38 F-type main sequence star with a classification of F7 V. It has 1.25^[9] times the mass of the Sun and radiates 2.4^[9] times the solar luminosity at an effective temperature of 6,194^[9] K. It lies at an angular separation of 25.1 arc seconds from the inner pair.^[3] They share a common proper motion, indicating they may be gravitationally bound with an orbital period of around 41,000 years.^[19]

The system has a peculiar velocity of 7004162000000000000♠16.2±4.2 km/s.^[6] It belongs to the Scorpius–Centaurus association and appears to be a member of the Gould's Belt.^[20]

半人馬座 ξ²

Centaurus constellation map.svg 半人馬座ξ2的位置
觀測資料 曆元 J2000.0
星座	半人馬座
星官
赤經	13h 06m 54.63940s[1]
赤緯	−49° 54′ 22.4823″[1]
視星等（V）	4.30[2] + 9.38[3]
特性
光谱分类	B1.5 V[4] or B2 IV[5] + F7 V[3]
U−B 色指数	−0.810[2]
B−V 色指数	−0.197[2]
天体测定
徑向速度 (Rv)	7001143000000000000♠+14.3±4.1[6] km/s
自行 (μ)	赤经：−26.15[1] mas/yr 赤纬：−12.03[1] mas/yr
视差 (π)	6.98 ± 0.24[1] mas
距离	470 ± 20 ly (143 ± 5 pc)
绝对星等 (MV)	−1.51[7]
軌道[8]
繞行週期 (P)	7.6497 d
偏心率 (e)	0.35
近心点 曆元 (T)	2418077.493 JD
近心點幅角 (ω) (secondary)	308.6°
半振幅 (K1) (primary)	38.8 km/s
詳細資料
ξ2 Cen A
質量	7000810000000000000♠8.1±0.1[4] M☉
表面重力 (log g)	7000411000000000000♠4.11±0.03[9]
亮度 (bolometric)	1,702[9] L☉
溫度	7004207900000000000♠20,790±335[9] K
自轉速度 (v sin i)	25[10] km/s
年齡	7001115000000000000♠11.5±3.7[4] Myr
ξ2 Cen B
質量	1.25[9] M☉
亮度	2.4[9] L☉
溫度	6,194[9] K
其他命名
半人馬座ξ2、CD−49° 7644、FK5 489、HD 113791、HIP 64004、HR 4942、SAO 223909[11]。
參考資料庫
SIMBAD	资料