Zeta Sagittarii

Starbox short
name=ζ Sagittarii
epoch=J2000.0
constell=Sagittarius
ra=19^h 02^m 36.7^s
dec=-29° 52' 49"
spectral=A2III+A4IV
appmag_v=+2.60
dist_ly=89.1 ± 3.3
dist_pc=27.3 ± 1
names=Ascella, 38 Sagittarii,
HR 7194, HD 176687,
SAO 187600, HIP 93506,
ADS 11950, CCDM 19026-2953

Zeta Sagittarii (ζ Sgr / ζ Sagittarii) is the third brightest star system in the constellation Sagittarius. It also has the traditional name Ascella from a Late Latin word meaning "armpit".

Ascella is a binary star, consisting of a spectral class A2 giant with an apparent magnitude of +3.26, and an A4 subgiant with apparent magnitude of +3.37. The orbital period of the binary system is 21 years. The two stars have a mean separation of 13.4 astronomical units (AU) and the eccentricity of their orbit is 0.205. Ascella has a faint, 10th magnitude companion, Zeta Sagittarii C, separated from the primary by a distance of 75 arcseconds.

Ascella is 90 light years from Earth. The combined apparent magnitude of the star system is +2.60.

In ancient Chinese astronomy, it is the 6th star of 6 stars in the Dipper or 'South Dipper' mansion of the Black Tortoise of the North.