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> Trifid nebula (M20) in Sagittarius
Trifid nebula (M20) in Sagittarius
author: Anglo-Australian Observatory/David Malin Images/Novapix
reference: a-neb65-14006
Image Size 300 DPI: 51 * 40 cm
The spectacular Trifid nebula (Messier 20) is one of the best known in the sky. It is a striking mixture of brilliant red light emitted from excited hydrogen gas and the soft blue glow of a reflection nebula. The blue arises from starlight, scattered by dust particles between the stars. The size of the particles is minute, similar to those of smoke, which also has a bluish hue. However, the scattered light is not a pure blue, and if we see it through a medium that is yellow (i.e. absorbs blue light) some green colouration remains. This effect can be seen in some of the darker parts of the faint reflection nebula that surrounds the Trifid, where partial absorption of light by foreground dust provides a yellow 'filter', producing shades of green. This image has been photographically enhanced using an unsharp mask.
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