A type Ia supernova occurs when a white dwarf star draws mass from a close companion star. When the dwarf’s mass exceeds a critical threshold, it collapses and explodes in a thermonuclear detonation. For mass to transfer, the gap between the stars must be relatively narrow.
Astronomy: Roen Kelly
Sirius B is not close enough to its companion to accrete hydrogen and reach the supernova threshold of 1.4 solar masses.
