This is IC 443 or to give it its common name, the Jellyfish Nebula, in the constellation of Gemini. Being classed a type II supernova remnant, it is the is the result of the death of a giant star about 8x the mass of our sun, which left a neutron star following the "explosion", the super dense core of the former star. The remnant gas from the supernova is interacting with molecular clouds which exist in the interstellar medium around the former star, which is most dense towards the upper left of the image, resulting in the more clumpy appearance at this position, giving the nebula its ditinctive shape.

Imaged in the light of Hydrogen Alpha, this particular wavelength of light occurs when hydrogen electrons fall from their third to their second lowest energy level, as is the case with the light emitted from the Jellyfish Nebula. The resuting light has a wavelength of 656.28nm (in air) which is towards the red end of the visible light spectrum and hence has been mapped to red in this image. The Ha filter used blocks out light at other wavelengths, resulting in a much sharper image,