Astronomers think that a supernova should go off in our own Milky Way galaxy every 50 years or so. When was the last one we've seen? Probably 1604. Yes, that's over 400 years ago. This being astronomy however, things will undoubtedly average out over the long run, but in the meantime, we're left without a recent supernova in our Galaxy to study. Luckily for us, astronomers from previous centuries were on the case.