T Pyxidis

T Pyxidis is what is called a recurring nova. The star, which is a white dwarf, accretes gas from a companion star. As the amount of matter increases in the white dwarf, it occasionally builds up to the point where there is a runaway thermonuclear reaction in the star, and it ejects large quantities of material.

T Pyxidis' average period for outbursts is about 19 standard years, but there are occasional disturbances which could cause the shells of gas repeatedly ejected by the star to not carry enough mass away, potentially creating a violent type Ia supernova, one of the most destructive events in the galaxy. Such an event could potentially be harmful to nearby inhabited star systems.