Gamma Sagittae (γ Sge / 12 Sagittae / HD 189319) is the brightest star in the constellation Sagitta, the arrow. Located at the tip of it, its apparent magnitude is +3.51. It is 274 light years from the Solar System.
Gamma Sagittae is a red giant of spectral type M0III (sometimes classified as type K) about 640 times more luminous than the Sun. Its radius, calculated from the measurement of its angular diameter by interferometry (6,18 milliseconds of arc), is 55 times larger than solar radio, or what is the same, 0.26 AU. It has a surface temperature of 4000 K. With a mass about 2.5 times greater than the solar mass, it is estimated that its age is 750 million years, much lower than the 4600 million years of age of our Sun. Unlike of the latter, he began his life as a bluish-white star of type B9, before becoming the giant star we see today. Although now it is slightly variable, in a short time it will become a Mira variable and it will end its life as a white dwarf.
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