Every Star That Could Destroy Earth Explained

Every Star That Could Destroy Earth Explained Sirius is the brightest star in Earth's night sky, a blazing blue-white beacon that ancient Egyptians used to predict the flooding of the Nile, and yet most people never stop to consider that it might one day try to kill us. The danger does not come from Sirius A, the dazzling main-sequence star roughly two times the mass of our Sun that we can see with the naked eye on any clear winter night. It comes from its companion, Sirius B, a white dwarf locked in a slow orbital dance with its brighter partner, completing one orbit roughly every fifty years. White dwarfs are the dense, cooling remnants of stars that have already died, and under the right conditions they can reignite in one of the most violent explosions the universe produces, a Type Ia supernova. For that to happen, a white dwarf needs to accrete enough mass from a nearby companion to push it past a critical threshold, roughly one point four times the mass of the Sun, a value astronomers call the Chandrasekhar limit.