... Shapley 1: An Annular Planetary Nebula . ... This strange structure is what can result when a normal star runs out of nuclear fuel in its core. At that time, the center condenses into a white dwarf while the outer atmospheric layers are expelled into space and appear as a planetary nebula. ... After a Sun-like star can no longer support fusion in its core, the center condenses into a white dwarf while the outer atmospheric layers are expelled into space and appear as a planetary nebula. ...