天市左垣八

**天市左垣八（東海，巨蛇座η）**
	東海（巨蛇座η）的位置（紅圈標示）。
觀測資料; 曆元 J2000
星座	巨蛇座
星官
赤經	18h 21m 18.60056s
赤緯	–02° 53′ 55.7766″
視星等（V）	3.260
特性
光谱分类	K0 III-IV
U−B 色指数	+0.643
B−V 色指数	+0.940
天体测定
徑向速度 (Rv)	+8.4 km/s
自行 (μ)	赤经：–547.75 mas/yr ; 赤纬：–701.42 mas/yr
视差 (π)	53.93 ± 0.18 mas
距离	60.5 ± 0.2 ly ; (18.54 ± 0.06 pc)
绝对星等 (MV)	+1.87
詳細資料
質量	2.0 M☉
半徑	5.897 ± 0.028 R☉
表面重力 (log g)	3.21
亮度	19 ± 1 L☉
溫度	4,890 K
金属量 [Fe/H]	–0.42 dex
自轉速度 (v sin i)	2.6 km/s
其他命名
	58 Serpentis, BD−02° 4599, HD 168723, HIP 89962, HR 6869, SAO 142241.
參考資料庫
SIMBAD	资料

天市左垣八（巨蛇座η），也稱為東海，是在88星座的巨蛇座中的一顆恆星。比較特別是它位於尾部，視星等為3.26等^[2]，是巨蛇座的第二亮星，肉眼就可以看見。視差測量估計它與地球的距離是60.5光年（18.5秒差距）^[1]。

這顆恆星比太陽大，質量為太陽的2倍，直徑是太陽的6倍^[6]^[7]。光譜與分類的K0 III-IV吻合^[3]，光度分類對應於恆星演化階段的次巨星和巨星。膨脹的恆星外層光度在有效溫度4,890K是太陽的19倍^[3]。在這個溫度下，它有典型的K型恆星的橙色色調^[11]。它有週期為0.09日的類太陽震盪（英语：solar-like oscillations） ^[12]。

天市左垣八以前被歸類為碳星，這使它成為天空中最亮的碳星但目前已經知道這種分類是錯誤的^[13]。

天市左垣八目前距離葛利斯710只有1.6光年^{[來源請求]}。

名稱

在中國，這顆恆星屬於星官天市左垣（Tiān Shì Zuǒ Yuán），意思是天上市場左邊的城牆，也是中國舊有的11個諸侯屬地之一。天市左垣包含的恆星有巨蛇座η、武仙座δ、武仙座λ、武仙座μ、武仙座ο、武仙座112、蛇夫座η、寶瓶座ζ、巨蛇座θ¹、蛇夫座ν和蛇夫座ξ ^[14]。因此，它也稱為天市左垣八 (Tiān Shì Zuǒ Yuán bā，意思是天上市場左側第八顆恆星，對應於東海的地區^[15]^[16]，可能就是指中國的東海 ^{[來源請求]}。

參考資料

^ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 van Leeuwen, F., Validation of the new Hipparcos reduction, Astronomy and Astrophysics, November 2007, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 , doi:10.1051/0004-6361:20078357
^ ^2.0 ^2.1 ^2.2 ^2.3 Cousins, A. W. J., Standardization of Broadband Photometry of Equatorial Standards, South African Astronomical Observatory Circulars, 1984, 8: 59, Bibcode:1984SAAOC...8...59C
^ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 Frasca, A.; et al, REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods and starspot parameters, Astronomy and Astrophysics, December 2009, 508 (3): 1313–1330, Bibcode:2009A&A...508.1313F, arXiv:0911.0760 , doi:10.1051/0004-6361/200913327
^ Wielen, R.; et al, Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, 1999, Bibcode:1999VeARI..35....1W
^ 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
^ ^6.0 ^6.1 Edvardsson, B., Spectroscopic surface gravities and chemical compositions for 8 nearby single sub-giants, Astronomy and Astrophysics, January 1988, 190 (1-2): 148–166, Bibcode:1988A&A...190..148E
^ ^7.0 ^7.1 Mérand, A.; et al, Interferometric radius and limb darkening of the asteroseismic red giant η Serpentis with the CHARA Array, Astronomy and Astrophysics, July 2010, 517: A64, Bibcode:2010A&A...517A..64M, doi:10.1051/0004-6361/200912103
^ Piau, L.; et al, Surface convection and red-giant radius measurements, Astronomy and Astrophysics, February 2011, 526: A100, Bibcode:2011A&A...526A.100P, arXiv:1010.3649 , doi:10.1051/0004-6361/201014442
^ 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
^ eta Ser -- Variable Star, SIMBAD (Centre de Données astronomiques de Strasbourg), [2012-01-19], （原始内容存档于2020-11-05）
^ 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）
^ Tabur, V.; et al, Period-luminosity relations of pulsating M giants in the solar neighbourhood and the Magellanic Clouds, Monthly Notices of the Royal Astronomical Society, December 2010, 409 (2): 777–788, Bibcode:2010MNRAS.409..777T, arXiv:1007.2974 , doi:10.1111/j.1365-2966.2010.17341.x
^ Antipova, L. I.; Boyarchuk, A. A. The chemical composition of the red giant η Ser. Astronomy Reports. 2001, 45 (9): 700. Bibcode:2001ARep...45..700A. doi:10.1134/1.1398919.
^ （中文） 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 978-986-7332-25-7.
^ （中文） AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 23 日（页面存档备份，存于互联网档案馆）
^ （中文） English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name （页面存档备份，存于互联网档案馆）, Hong Kong Space Museum. Accessed on line November 23, 2010.

[aaa474_2_653-1] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 van Leeuwen, F., Validation of the new Hipparcos reduction, Astronomy and Astrophysics, November 2007, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 , doi:10.1051/0004-6361:20078357

[saaoc8_59-2] 2.0 ^2.1 ^2.2 ^2.3 Cousins, A. W. J., Standardization of Broadband Photometry of Equatorial Standards, South African Astronomical Observatory Circulars, 1984, 8: 59, Bibcode:1984SAAOC...8...59C

[aaa508_3_1313-3] 3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 Frasca, A.; et al, REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods and starspot parameters, Astronomy and Astrophysics, December 2009, 508 (3): 1313–1330, Bibcode:2009A&A...508.1313F, arXiv:0911.0760 , doi:10.1051/0004-6361/200913327

[scfs-4] Wielen, R.; et al, Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, 1999, Bibcode:1999VeARI..35....1W

[aj135_3_892-5] 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

[aaa190_1_148-6] 6.0 ^6.1 Edvardsson, B., Spectroscopic surface gravities and chemical compositions for 8 nearby single sub-giants, Astronomy and Astrophysics, January 1988, 190 (1-2): 148–166, Bibcode:1988A&A...190..148E

[aaa517_A64-7] 7.0 ^7.1 Mérand, A.; et al, Interferometric radius and limb darkening of the asteroseismic red giant η Serpentis with the CHARA Array, Astronomy and Astrophysics, July 2010, 517: A64, Bibcode:2010A&A...517A..64M, doi:10.1051/0004-6361/200912103

[aaa526_A100-8] Piau, L.; et al, Surface convection and red-giant radius measurements, Astronomy and Astrophysics, February 2011, 526: A100, Bibcode:2011A&A...526A.100P, arXiv:1010.3649 , doi:10.1051/0004-6361/201014442

[aj135_1_209-9] 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

[SIMBAD-10] ta Ser -- Variable Star, SIMBAD (Centre de Données astronomiques de Strasbourg), [2012-01-19], （原始内容存档于2020-11-05）

[csiro-11] 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）

[mnras409_2_777-12] Tabur, V.; et al, Period-luminosity relations of pulsating M giants in the solar neighbourhood and the Magellanic Clouds, Monthly Notices of the Royal Astronomical Society, December 2010, 409 (2): 777–788, Bibcode:2010MNRAS.409..777T, arXiv:1007.2974 , doi:10.1111/j.1365-2966.2010.17341.x

[Antipova-13] Antipova, L. I.; Boyarchuk, A. A. The chemical composition of the red giant η Ser. Astronomy Reports. 2001, 45 (9): 700. Bibcode:2001ARep...45..700A. doi:10.1134/1.1398919.

[14] （中文） 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 978-986-7332-25-7.

[15] （中文） AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 23 日（页面存档备份，存于互联网档案馆）

[16] （中文） English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name （页面存档备份，存于互联网档案馆）, Hong Kong Space Museum. Accessed on line November 23, 2010.

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天市左垣八

名稱

參考資料

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