"Sirius is a first magnitude star (HR 2491 HD 48915 Flamsteed Number: 9 Bayer Letter: Alpha) in the Constellation of Canis Major, with a visual Magnitude of -1.46. Sirius is also known as Canicula; the Dog Star and Aschere. Sirius is 2.01 times the size of the Sun and the brightest star in our heavens. The heliacal rising of the dog star signalled the most searing heat of the Summer, hence the term 'dog days.'. The star is most easily found by tracing the belt of Orion downwards. Sirius is a binary star with a white dwarf companion, Sirius B.