The universe is a dangerous place. Black holes, gamma ray bursts and pulsars could all seriously damage or even destroy our planet if they were close enough, but the fact of the matter is that there is nothing in our vicinity that poses an immediate threat, at least for the next few billion years. The nearest star that could go supernova is Betelgeuse, 640 light years away. In fact this star could be about to go supernova in one minute, one year or a thousand years; all astronomers know is that it has reached its Chandrasekhar limit and it could blow at any second, when it will appear as one of the brightest stars (other than the Sun) in the night sky. But just how close would a star have to be to cause irreparable damage to Earth?
100 light years away
At this distance a supernova poses no threat to Earth. The intensity of a supernova’s energy dissipates exponentially, so other than observing a bright star in the night sky we would experience no effect on Earth. The closest star to Earth that could go supernova is Betelgeuse, 640 light years away, but it poses no threat to us.
50 light years away
In several billion years it is possible that a star closer to home will go supernova. If one did so about 50 light years from Earth, it is likely that it would shear the ozone off our planet, in turn also destroying the Earth’s magnetic field. This would make our world all but uninhabitable.
1 light year away
The closest star to Earth is the red dwarf Proxima Centauri just over four light years away, but there is no chance of it going supernova. Theoretically, though, if a star were to go supernova one light year away from Earth it would rip our planet and the entire solar system to shreds. The force of the shockwaves would easily destroy every nearby celestial object, and leave our solar system as a nebula remnant that would eventually lead to the formation of new stars and planets.