畢宿四

畢宿四（金牛座γ）
γ Tauri
	; 畢宿四在畢宿星團的位置; （最右邊的紅點）
觀測資料; 曆元 J2000
星座	金牛座
星官	畢宿畢
赤經	04h 19m 47.6037s
赤緯	+15° 37′ 39.512″
視星等（V）	3.654
特性
光譜分類	G8III
U−B 色指數	+0.84
B−V 色指數	+0.99
天體測定
徑向速度 (Rv)	38.7 ± 0.9 km/s
自行 (μ)	赤經：115.29 mas/yr ; 赤緯：-23.86 mas/yr
視差 (π)	21.17 ± 1.17 mas
距離	154 ± 9 ly ; (47 ± 3 pc)
絕對星等 (MV)	0.22
詳細資料
質量	2.70 ± 0.13 M☉
半徑	13.4 ± 0.2 R☉
表面重力 (log g)	2.58-2.61
亮度	85 L☉
溫度	4,844 ± 47 K
金屬量
自轉速度 (v sin i)	4 km/s
年齡	4.3–5.3 × 108 年
其他命名
	Hyadum I, Prima Hyadum, 54 Tauri, HR 1346, HD 27371, HR 1346, BD+15°612, FK5 159, HIP 20205, SAO 93868, GC 5226, CCDM 04198+1538.

畢宿四，即金牛座γ（γ Tau，γ Tauri）是一顆位於金牛座的恆星，它是離太陽系最近的疏散星團——畢宿星團的成員之一。它和畢宿星團的其他亮星以及附近的畢宿五一起組成金牛座的頭部。

特徵

畢宿四是一顆G8型或K0型巨星^[2]^[3]，視星等為+3.65。它距離畢宿星團的中心僅有2.5秒差距。這顆恆星已經度過主序星階段，現在膨脹成為紅巨星，核心使用氦核聚變來提供能量^[11]。它的年齡估計介於4.3億年^[3]至5.3億年^[6]之間。相對的，畢宿星團的年齡約為6.25億年，存在0.5億年的誤差^[12]。

天文學家對畢宿四的視差測量為21.17±1.17角分，據此計算出它距離地球約154光年（47秒差距）。畢宿四的角直徑已經為威爾遜山天文台的高解像度天文中心（CHARA array）所測量，它的精度為+/- 2%。通過對畢宿四周邊昏暗效應的校正，計算出恆星的半徑約是太陽半徑的13.4倍^[7]。畢宿四的光度是太陽光度的85倍^[3]，質量是太陽質量的2.7倍^[6]，表面溫度約為4970K。

命名

在中國古代星官系統中，畢宿四屬於西方白虎七宿中畢宿第四星，這也是畢宿四名字的來由^[13]^[14]。

它的西方傳統名字為Hyadum I^[10]，在拉丁語中是「畢宿星團第一星」的意思。

畢宿四的拜耳命名法為金牛座γ，佛氏命名為金牛座54，HD星表中編號第27371，依巴谷星表編號第20205。

參考資料

^ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 Perryman, M. A. C.; et al, The Hipparcos Catalogue, Astronomy & Astrophysics, 1997, 323: L49–L52, Bibcode:1997A&A...323L..49P
^ ^2.0 ^2.1 ^2.2 NSV 1553 - Variable Star. SIMBAD. Centre de Données astronomiques de Strasbourg. [2009-09-22]. （原始內容存檔於2016-03-03）.
^ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 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.
^ ^4.0 ^4.1 Johnson, H. L.; Morgan, W. W. Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas. Astrophysical Journal. 1953, 117: 313–352. Bibcode:1953ApJ...117..313J. doi:10.1086/145697.
^ Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Batten, Alan Henry; Heard, John Frederick (編). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. June 20–24, 1966 [2009-09-10]. （原始內容存檔於2019-06-26）.
^ ^6.0 ^6.1 ^6.2 ^6.3 da Silva, L.; et al. Basic physical parameters of a selected sample of evolved stars. Astronomy and Astrophysics. November 2006, 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160  . doi:10.1051/0004-6361:20065105.
^ ^7.0 ^7.1 ^7.2 ^7.3 Boyajian, Tabetha S.; et al. Angular Diameters of the Hyades Giants Measured with the CHARA Array. The Astrophysical Journal. February 2009, 691 (2): 1243–1247. Bibcode:2009ApJ...691.1243B. doi:10.1088/0004-637X/691/2/1243.
^ Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants. Astronomy and Astrophysics. March 2008, 480 (1): 91–101. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788.
^ Bernacca, P. L.; Perinotto, M. A catalogue of stellar rotational velocities. Contributi Osservatorio Astronomico di Padova in Asiago. 1970, 239 (1). Bibcode:1970CoAsi.239....1B.
^ ^10.0 ^10.1 Allen, R. H. Star Names: Their Lore and Meaning Reprint. New York, NY: Dover Publications Inc. 1963: 390. ISBN 0486210790.
^ de Bruijne, J. H. J.; Hoogerwerf, R.; de Zeeuw, P. T. A Hipparcos study of the Hyades open cluster. Improved colour-absolute magnitude and Hertzsprung-Russell diagrams. Astronomy and Astrophysics. February 2001, 367 (1): 111–147. Bibcode:2001A&A...367..111D. arXiv:astro-ph/0011565  . doi:10.1051/0004-6361:20000410.
^ da Silva, L.; et al. Basic physical parameters of a selected sample of evolved stars. Astronomy and Astrophysics. November 2006, 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160  . doi:10.1051/0004-6361:20065105.
^ 香港太空館 - 研究資源 - 亮星中英對照表互聯網檔案館的存檔，存檔日期2010-08-11., Hong Kong Space Museum. Accessed on line November 23, 2010.
^ 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 9789867332257.

[hipparcos-1] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 Perryman, M. A. C.; et al, The Hipparcos Catalogue, Astronomy & Astrophysics, 1997, 323: L49–L52, Bibcode:1997A&A...323L..49P

[SIMBAD-2] 2.0 ^2.1 ^2.2 NSV 1553 - Variable Star. SIMBAD. Centre de Données astronomiques de Strasbourg. [2009-09-22]. （原始內容存檔於2016-03-03）.

[pasj60-3] 3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 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.

[yerkes53-4] 4.0 ^4.1 Johnson, H. L.; Morgan, W. W. Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas. Astrophysical Journal. 1953, 117: 313–352. Bibcode:1953ApJ...117..313J. doi:10.1086/145697.

[5] Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Batten, Alan Henry; Heard, John Frederick (編). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. June 20–24, 1966 [2009-09-10]. （原始內容存檔於2019-06-26）.

[aaa458-6] 6.0 ^6.1 ^6.2 ^6.3 da Silva, L.; et al. Basic physical parameters of a selected sample of evolved stars. Astronomy and Astrophysics. November 2006, 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160  . doi:10.1051/0004-6361:20065105.

[apj691-7] 7.0 ^7.1 ^7.2 ^7.3 Boyajian, Tabetha S.; et al. Angular Diameters of the Hyades Giants Measured with the CHARA Array. The Astrophysical Journal. February 2009, 691 (2): 1243–1247. Bibcode:2009ApJ...691.1243B. doi:10.1088/0004-637X/691/2/1243.

[8] Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants. Astronomy and Astrophysics. March 2008, 480 (1): 91–101. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788.

[9] Bernacca, P. L.; Perinotto, M. A catalogue of stellar rotational velocities. Contributi Osservatorio Astronomico di Padova in Asiago. 1970, 239 (1). Bibcode:1970CoAsi.239....1B.

[hinckley-10] 10.0 ^10.1 Allen, R. H. Star Names: Their Lore and Meaning Reprint. New York, NY: Dover Publications Inc. 1963: 390. ISBN 0486210790.

[11] Bruijne, J. H. J.; Hoogerwerf, R.; de Zeeuw, P. T. A Hipparcos study of the Hyades open cluster. Improved colour-absolute magnitude and Hertzsprung-Russell diagrams. Astronomy and Astrophysics. February 2001, 367 (1): 111–147. Bibcode:2001A&A...367..111D. arXiv:astro-ph/0011565  . doi:10.1051/0004-6361:20000410.

[12] Silva, L.; et al. Basic physical parameters of a selected sample of evolved stars. Astronomy and Astrophysics. November 2006, 458 (2): 609–623. Bibcode:2006A&A...458..609D. arXiv:astro-ph/0608160  . doi:10.1051/0004-6361:20065105.

[13] 香港太空館 - 研究資源 - 亮星中英對照表互聯網檔案館的存檔，存檔日期2010-08-11., Hong Kong Space Museum. Accessed on line November 23, 2010.

[14] 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 9789867332257.

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觀測資料曆元 J2000
畢宿四在畢宿星團的位置（最右邊的紅點）
星座	金牛座
星官	畢宿畢
赤經	04^h 19^m 47.6037^s^[1]
赤緯	+15° 37′ 39.512″^[1]
視星等（V）	3.654^[2]
特性
光譜分類	G8III^[3]
U−B 色指數	+0.84^[4]
B−V 色指數	+0.99^[4]
天體測定

徑向速度 (R_v)	38.7 ± 0.9^[5] km/s
自行 (μ)	赤經：115.29^[1] mas/yr 赤緯：-23.86^[1] mas/yr
視差 (π)	21.17 ± 1.17^[1] mas
距離	154 ± 9 ly (47 ± 3 pc)
絕對星等 (M_V)	0.22^[3]

詳細資料

質量	2.70 ± 0.13^[6] M_☉
半徑	13.4 ± 0.2^[7] R_☉
表面重力 (log g)	2.58-2.61^[7]
亮度	85^[3] L_☉
溫度	4,844 ± 47^[7] K
金屬量	${\begin{smallmatrix}{\frac {Fe}{H}}\ =\ 0.11\end{smallmatrix}}$ ^[8]
自轉速度 (v sin i)	4^[9] km/s
年齡	4.3–5.3 × 10⁸^[3]^[6] 年

其他命名
Hyadum I, Prima Hyadum,^[10] 54 Tauri, HR 1346, HD 27371, HR 1346, BD+15°612, FK5 159, HIP 20205, SAO 93868, GC 5226, CCDM 04198+1538.^[2]