(entry perma-link)



Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space where once was the most massive item you can actually have without ripping space. The explosion alone triggers alchemy on a suprasolar scale, converting stars' worth of matter into new radioactive elements. While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. By NASA calculations there are 1 billion supernovae per year, or 30 supernovae per second in the observable Universe!