I am looking for a short story about an astronaut conducting radiation measurements on the dark side of the moon (or maybe mars). The astronaut ponders the strange measurement results when it dawns at him that the sun must have gone supernova and earth probably scorched. He returns to earth as the last living human, but discovers that other lifeforms (I believe to remember it was about a butterfly) seem to have survived and despite the end of humanity, life was going to continue.
I read this story about 30 years ago in an anthology of short stories which my future wife brought from our local library. Unfortunately, I don't remember any of the other stories and authors, but I believe they were all well known names and not obscure pulp fiction authors.
Today it strikes me, how naïve the thought was, that libraries and books were for eternity and that everything I'd read would be effortlessly available for me in the library to read again when ever I wanted.