Epoch J2000.0 Equinox J2000.0
|Right ascension||19h 22m 38.3s|
|Declination||−44° 27' 32"|
|Apparent magnitude (V)||+3.96|
|Distance||378 ± 42 ly
(116 ± 13 pc)
The Bayer designation Beta Sagittarii (Beta Sgr, β Sagittarii, β Sgr) is shared by two star systems, β¹ Sagittarii and β² Sagittarii, in the constellation Sagittarius. The two stars are separated by 0.36° in the sky. Beta Sagittarii also has the traditional name Arkab.
Beta¹ Sagittarii (Beta¹ Sgr, β¹ Sagittarii, β¹ Sgr), also called Arkab Prior since it leads β² across the sky, is a binary star lying 378 light years from Earth. Arkab Prior A is a spectral type B9 main sequence dwarf which has an apparent magnitude of +3.96. Arkab Prior B is a type A3 dwarf with an apparent magnitude of +7.4. The two stars are separated in the sky by 28 arcseconds, which puts them at least 3300 astronomical units apart.
|Right ascension||19h 23m 13.2s|
|Declination||-44° 47' 59"|
|Apparent magnitude (V)||+4.27|
|Distance||139 ± 5 ly
(43 ± 2 pc)
Beta² Sagittarii (Beta² Sgr, β² Sagittarii, β² Sgr), also called Arkab Posterior since it trails β¹ across the sky, is a spectral type F2 giant which has an apparent magnitude of +4.27. It is 137 light years from Earth.
Name and etymology
- The name Arkab is from the Arabic عرقوب carqūb meaning hamstring
- *In Chinese, 天淵 (Tiān Yuān), meaning Celestial Spring, refers to an asterism consisting of β¹ Sagittarii, β² Sagittarii, and α Sagittarii, . Consequently, β¹ Sagittarii and β² Sagittarii themselves are known as 天淵一 (Tiān Yuān yī, English: the First Star of Celestial Spring.) and 天淵二 (Tiān Yuān èr, English: the Second Star of Celestial Spring.)
- These two Betas star, together with α Sgr too, were Al Ṣuradain (ألسردين), the two Surad, desert birds.
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 2 日
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 357. ISBN 0-486-21079-0. Retrieved 4 September 2012.
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