I have been reviewing some of my files of photographs and came across these of the Ring Nebula, one of my favourite photographic targets in space.
The Ring Nebula (aka Messier 57 or NGC6720) is a planetary nebula found in the constellation Lyra. It is caused by a shell of ionised gas, which has been expelled from a red giant star in the process of turning into a white dwarf. The inner ring gives a blue-green hue, whilst the outer rings give a reddish hue, something which can just be seen in the close-up photos. The nebula is 2300 light-years from Earth and measurements have shown that the gas ring is expanding all way from the central star.