Copyright: Adam Block/NOAO/AURA/NSF
M57 - The Ring Nebula - (shown here in false colour) is another example of a planetary nebula, formed when a giant star, nearing the end of its life, sheds its outer layers of gas and contracts into a white dwarf. The ultraviolet radiation from the white dwarf collides with the gas, causing it to glow in various colours according to its chemical make-up.
M57 is thought to lie around 4000 ly away and at magnitude 9.5 requires a telescope to be seen. The central white dwarf glows at a feeble magnitude 16.