... Tonight's Sky . ... Star Atlas . ... Supernova showered Earth with radioactive debris . ... Gravitational wave search provides insights into galaxy evolution and mergers . ... Nearby supernova factory models early universe . ... In this rendition of the early universe, the sky is ablaze with primeval starburst galaxies, while giant elliptical and spiral galaxies have yet to form. ... The most massive stars self-detonate as supernovas, which explode across the sky like a string of firecrackers. ...