Zeta Sagittarii

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ζ Sagittarii
Observation data
Epoch J2000.0
Constellation
(pronunciation)		 Sagittarius
Right ascension 19h 02m 36.7s
Declination -29° 52' 49"
Apparent magnitude (V) +2.60
Distance 89.1 ± 3.3 ly
(27.3 ± 1 pc)
Spectral type A2III+A4IV
Other designations
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.

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