Sirius is a binary star system that is located in the constellation Canis Major, or the Great Dog. It is considered the brightest star in the night sky, which is why it is also known as the Dog Star.Sirius is composed of two stars, Sirius A and Sirius B. Sirius A is a main-sequence star that is twice as massive as the sun and over 20 times more luminous. Sirius B, on the other hand, is a white dwarf star that is about the size of Earth but much more massive. It is the first white dwarf star t...