The Alpha Centauri system is 4.37 Light Years away.
So if one of it’s stars went nova we wouldn’t know about it for 4.37 years.
How much time is there between seeing the explosion and it’s physical effects on our system?
Just curious.
Much slower than the speed of light (seeing it) obviously. The answer is in here, “One of these isotopes is iron-60 which decays with a half-life of 2.6 million years, unlike its stable cousin iron-56.” It would have to have been a relatively close star but with the isotope being created in the supernova and knowing, as they must, the age of the strata the isotope is found in, they can have a fair idea of the star’s distance and from that you could calculate the speed.