Sirius A main sequence star. Animation of the location in the night sky and the properties of the A-type star Sirius A (Alpha Canis Majoris A), in the constellation Canis Major. Sirius A is a main sequence star, 1.71 times the width of the Sun (over 2.3 million kilometres across) and 2.02 times the Sun's mass. Sirius A, the companion of Sirius B in the Alpha Canis Majoris binary system, is 200-300 million years old. It will enter its red giant stage in around billion years time. Sirius A is spectral type A1, with a luminosity class of Vm. It is some 25.4 times more luminous than the Sun and has an atmospheric temperature of 9940 Kelvin. Its spectrum includes strong hydrogen lines and some ionised metal lines. For Sirius B, see animation K005/3276.