DUDE! I'm not living through 600+ more family reunions just to see a star blow up and gamma-burst humanity into crispy critters. I've got some dying to do before then. Actually it could have exploded 600 years ago, say tomorrow, that means we would see the first light of the explosion tomorrow and get any gamma rays(Hopefully not)at that time also, or not as the case may be.
Our current (600 year old) view of it shows it contracting at about 1% per year. Contractions should(did) continue for some time and accelerate, with a tipping point that is/will be noticeable reached before we can safely say it exploded today(600 years ago).
We need a better time sense grammatical structure, that includes what we observe with the time lag of observation if we're going to discuss this in English. ;)
/johnny