A search for the remains of a nearby stellar explosion has come up empty. Astronomers observed the blast site of the supernova, SN 1987A, with the Hubble Space Telescope, but could not find any sign of the dense stellar core.
http://www.space.com/scienceastronomy/050606_missing_core.html
http://www.space.com/scienceastronomy/050606_missing_core.html