The Crescent Nebula, also known as NGC 6888, is a nebula lighted up by a central Wolf-Rayet star, WR 136, whose ultraviolet radiation is responsible for heating and ionising most of the material ejected by the star during previous evolutionary phases.
The strong winds blown by the central, massive star are interacting with the previously expelled material and as a result, the nebula shows a complex structure which resembles a crescent red Moon.
This image of the Crescent Nebula or NGC 6888 was obtained using the Wide Field Camera on the Isaac Newton Telescope. It is a three-colour composite made from data collected using filters to isolate the light emitted by hydrogen alpha (H-alpha) and doubly ionised oxygen (OIII) atoms, and coded in the image as red, green (25% H-alpha and 75% OIII) and blue.
This image was obtained and processed by members of the IAC astrophotography group (A. Oscoz, D. L?pez, P. Rodr?guez-Gil and L. Chinarro) and it was selected as “Astronomy Picture of the Day”, 15th September 2009.