The dense, hot core left behind after a low- or intermediate-mass star expels its outer layers. White dwarfs are composed mostly of electron-degenerate matter and no longer undergo fusion.
Source: chandra.harvard.edu
30/04/2011

Tycho! Tycho! burning bright In the darkness of the night, What exploding white dwarf star Did frame thy remnant from afar, In the distant deep dark skies Under gaze of human eyes? Seen by mortals and their ma Named for one called Tycho Brahe.