<P> As ozone in the atmosphere prevents most energetic ultraviolet radiation reaching the surface of the earth, astronomical data in these wavelengths has to be gathered from satellites orbiting above the atmosphere and ozone layer . Most of the light from young hot stars is in the ultraviolet and so study of these wavelengths is important for studying the origins of galaxies . The Galaxy Evolution Explorer, GALEX, is an orbiting ultraviolet space telescope launched on April 28, 2003, which operated until early 2012 . </P> <Ul> <Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P> </Li> </Ul> <Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P> </Li> <P> This GALEX image of the Cygnus Loop Nebula could not have been taken from the surface of the Earth because the Ozone Layer blocks the ultra-violet radiation emitted by the nebula . </P>

Briefly explain why ozone is an important atmospheric gas