Astronomy Picture of the Day . ... Hubble Heritage Team ( STScI / AURA ), NASA Explanation: Except for the rings of Saturn , the Ring Nebula (M57) is probably the most famous celestial band. This planetary nebula's simple, graceful appearance is thought to be due to perspective -- our view from planet Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. ... 2003 2004 . ... Publications with keywords: M 57 - Ring Nebula - planetary nebula . ...