Epoch J2000.0 Equinox J2000.0
|Right ascension||18h 13m 45.8s|
|Declination||−21° 03′ 32″|
|Apparent magnitude (V)||+3.84|
|Distance||> 3912 ly
(> 920 pc)
The primary component in this system, Polis A, is a type B giant star with a total luminosity of 180,000 times that of the Sun and a radius of 115 times solar. Its mass is 23 times the solar mass while it has a surface temperature of 11,100 kelvins.
Polis A is an eclipsing binary, bringing the total of stars in the system to six. The primary component is a spectral type B8 supergiant and the companion is a type B2 giant. The orbital period of the binary is 180.55 days. Due to occultation of the primary by the companion, the apparent magnitude of Polis A varies between +3.84 and +3.96.
The remaining components are very weakly bound to the Polis system.
from Polis A
from Polis A
|Polis B||+11.5||16.9 arcseconds||42 200 AU or 0.67 ly|
|Polis C||+13.5||25.8 arcseconds||64 500 AU or 1.02 ly|
|Polis D||+9.9||48.5 arcseconds||121 200 AU or 1.92 ly|
|Polis E||+9.4||50.0 arcseconds||125 000 AU or 1.98 ly|
Name and etymology
- The traditional name Polis is derived from a Coptic word meaning foal.
- In Chinese, 斗 (Dǒu), meaning Dipper, refers to an asterism consisting of μ Sagittarii, φ Sagittarii, λ Sagittarii, σ Sagittarii, τ Sagittarii and ζ Sagittarii. Consequently, μ Sagittarii itself is known as 斗宿三 (Dǒu Sù sān, English: the Third Star of Dipper.)