Ji Su Er , i.e Sagittarius δ （ δ Sgr ， Bayer designation ）Or Sagittarius 19 （ Franstide nomenclature ）Is a multi star system located in Sagittarius, 306 away from Earth Light year 。 The main star Ji Su Er A is one Type K3 Star, with brightness 1180 times of the sun, diameter 62 times of the sun, and mass 5 Solar mass ， Apparent magnitude Is 2.72. In addition, it has three dim companion stars: Jiji B, apparent magnitude 14, away from the main star (Jiji A) 26 Angular second ； Ji Su Er C, the apparent star magnitude is 15 degrees, 40 angular seconds away from the main star;
Jisu 2D, apparent magnitude 13, 58 angular seconds away from the main star;
In fact, he has only one star, and the so-called B, C and D just look close
