Why are inhabitants of Earth currently safe from the immediate light flash and trailing shockwave of Alpha Centauri?

Alpha Centauri is about 4.24 light-years away, exceeding the lethal range for those immediate effects.

Alpha Centauri is recognized as the closest star system to our own, situated approximately 4.24 light-years away. This distance places it outside the critical proximity thresholds required for the most immediate supernova hazards to cause catastrophic damage to Earth. Specifically, the text notes that this distance means Earth is safe from both the initial, intensely bright light flash and the subsequent arrival of the physical shockwave, as the necessary lethal range for those two effects is significantly smaller than 4.24 light-years (the shockwave is lethal within 1 LY, and the light flash causes serious harm much closer than 4.24 LY).