AAO image reference UKS 7. « Previous || Next »
Top left is NE. Image width is about 30 arc min.
Image and text © 1979-2010, Australian Astronomical Observatory
Photograph from UK Schmidt plates by David Malin.
The Trifid Nebula is a fine example of an object which combines emission and reflection nebulosity. The striking red emission nebula surrounds a small group of very hot stars, seen in more detail in the this AAT photograph. Energetic radiation from these stars causes part of the enveloping but otherwise invisible hydrogen cloud to fluoresce and emit its characteristic monochromatic red light. Beyond the limits of the emission nebula sufficient starlight escapes at longer wavelengths for it to be scattered by the dust grains associated with the gas. The scattering produces a faint blue reflection nebula around the irregular sphere of red emission. To the north, a yellowish star which is too cool to create an emission nebula is embedded in its own hazy blue reflection. The Trifid nebula is in Sagittarius but its distance is not well known -- about 5000 light years is commonly quoted.
AAT 12. The Trifid nebula, Messier 20
AAT 12a. The Trifid nebula, Messier 20 (wide field)
AAT 69. Reflection nebula around M20
AAT 69a. Reflection nebula around M20 (wide field)
AAT 30. The stars that excite the Trifid nebula
AAT 31. The Hourglass nebula in M8
AAT 31a. The Lagoon and Hourglass nebulae in M8
UKS 26. The field of M8 and M20 in Sagittarius
UKS 26a. The field of M8 and M20 in Sagittarius (wide field)
Constellation of Sagittarius (external site)
For details of object position and photographic exposure, search technical table by UKS reference number.
| emission nebulae
| reflection nebulae
| dark nebulae
| planetary nebulae
| star clusters
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