AAO image reference AAT 29a. « Previous || Next »
Top left is NE. Image width is about 8 arc min
Image and text © 1979-2010, Australian Astronomical Observatory, photograph by David Malin.
The central 'star' of the three groups forming the asterism of Orion's Sword is in reality a nebula, and is clearly nebulous to the unaided eye when seen under a dark sky. At the heart of the most luminous nebulosity shimmer a handful of stars known as the Trapezium cluster, visible in binoculars. These are the brightest members of a substantial cluster of stars, most of which are still hidden in the dusty recesses of the Orion nebula against which they are seen. The stars of the Trapezium provide much of the energy which makes the brilliant Orion Nebula visible and are at a distance of about 1350 light years.
This image was made with three, 30-second exposures at the prime focus of the the Anglo-Australian Telescope, using a process that involved an unsharp mask. The three associated images (AAT 29a) and (AAT 29b) are made from the same AAT plates, and show how the basic data can be presented in different ways using unsharp masks with different characteristics.
AAT 29. The Orion nebula
AAT 29b. The Orion nebula (no unsharp mask)
Constellation of Orion (external site)
For details of photographic exposure, search technical table by AAT reference number
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