AAO image reference AAT 69. « Previous || Next »
Top left is NE. Image width is about 29 arc min
Image and text © 1991-2010, Australian Astronomical Observatory, photograph by David Malin.
The spectacular Trifid nebula (Messier 20) is one of the best known in the sky and it is in a rich star-field inSagittarius. 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.
Related Images
AAT 12. The Trifid nebula, Messier 20
AAT 12a. The Trifid nebula, Messier 20 (wide field)
AAT 30. The stars that excite the Trifid nebula>
AAT 69a. Reflection nebula around M20 (wide field)
UKS 7. Reflection nebula around M20
UKS 26. The field of M8 and M20 in Sagittarius
Constellation of Sagittarius (external site)
For details of photographic exposure, search technical table by AAT reference number.