![]() Caption:The Horsehead Nebula in Orion is widely recognized because it has the distinctive dark outline of the head of a horse, but the mechanisms that created it are seen throughout the Milky Way. Here we see two bright stars whose radiant energy is beating down on to the surface of a dark cloud, very similar to that in Orion. The opacity of the cloud protects the fragile molecules within from the energetic radiation of nearby stars, but as its surface is gradually warmed and eroded, the delicate organic molecules are destroyed and the hydrogen released glows as a distinctive emission nebula. Copyright:(c) 1992 Anglo-Australian Telescope Board, photograph by David Malin Credit: |
![]() Caption:Sometimes the dust that hides so much of our galaxy from us forms thin veils or streaks, or, as here, dense clouds, obscuring what is probably a more or less uniform field of faint stars. Such old stars appear slightly yellow on color pictures. The 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. Copyright:(c) 1992 Anglo-Australian Telescope Board, photograph by David Malin Credit: |