Nebula by reflexion in NGC 6188 in the Altar - Reflection nebula in NGC 6188...

Nebula by reflexion in NGC 6188 in the Altar - Reflection nebula in NGC 6188 in Ara - Nebula NGC 6188 is located about 4000 years - light from Earth. Image obtained by Siding Spring's 3.9m telescope. The fainter stars here are cool, like those that orbit the inner 'bulge' of the Milky Way and appear slightly yellow on colour pictures. The foreground patch of dust that crosses this photograph must be illuminated by energetic radiation from stars that are much hotter than those in the background because hydrogen, which is associated with the dust, has been excited into a vivid red fluorescence by absorbing the invisible ultraviolet light. Here and there a few bright but cooler stars are caught up in the outskirts of dust clouds and some of their light is scattered to produce the blue reflection nebulae