Astronomy Picture of the Day . Shapley 1: An Annular Planetary Nebula . ... The center condenses into a white dwarf while the outer atmospheric layers are expelled into space and appear as a planetary nebula. ... Ganymede: The Largest Moon in the Solar System . ... A jet stretching nearly a million light years has been imaged emanating from galaxy Pictor A. The thin jet of electrons and protons shoots out at nearly light-speed likely from the vicinity of a large black hole at the galaxy center. ...