The closest one is Alpha Centauri, 4.37 light years away.
If it exploded, it would happen……
I mean, it’s fine that it be an explosion and so on, but the most important thing that would happen is that we could see it in the sky (the explosion) because even if the sun exploded nothing would happen (that is, the explosion would not harm us directly ), it would have to be much bigger.
First of all, we will define “near”: to be affected by the outburst, it would have to be at least 30 light-years away for a supernova of a star 10 times the mass of the Sun.
Only if the star were really close, as in the case of Alpha Centauri (4.3 light years), the Earth and the solar system would be directly affected by the explosion, sweeping our atmosphere and leaving us exposed in the event that we survived that first explosion.
If they survive, the nights would be really cold, several tens of degrees below zero, with all that this entails for the survival of the species. We wouldn’t last long. That’s assuming we had any air to breathe, which seems unlikely.
But still Alpha Centauri doesn’t have anywhere near the mass to do that.
The candidate that is thought to be able to explode earlier is Betelgeuse, in the constellation of Orion, located about 640 light years away. Maybe it has already exploded. If so, from the moment of the explosion, it will take us 640 years to find out, which is the time it will take for light to reach us.