Horsehead Nebula, NGC 2024 and IC 434
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Horsehead Nebula, NGC 2023, NGC 2024 and IC 434, Flame nebula, Barnard 33
Top is W, left is N. Image width is about 100 arc min
Image and text © 1980-2010, Australian Astronomical Observatory
Photo from UK Schmidt plates by David Malin.

This distinctive red emission nebula (IC 434) is the result of radiation from sigma Orionis interacting with the surface of a dusty cloud of gas from which projects the dark shape of the head of a horse. Sigma is the second brightest star in the picture and is at about the same distance from the Sun as the nebula. The brightest star here is zeta Orionis, easily visible to the unaided eye as the easternmost star in the line of three which form Orion's Belt. Partly obscured by the glare of zeta is the curious yellowish nebula NGC 2024, whose energy comes from stars hidden in the dark lane, while other nebulae simply reflect the light of embedded hot stars and appear blue. All the nebulous objects and the dark cloud of dust that hides distant stars are about 1350 light years away.

Related images
UKS 1a.   The Horsehead Nebula and NGC 2023 (wide field, with and without unsharp mask)
AAT 36.    The Horsehead Nebula and NGC 2023 (portrait format)
AAT 36a.  The Horsehead Nebula and NGC 2023 (landscape format, wide field)
UKS 23.    Faint nebulosity near Orion and Horsehead Nebulae
Constellation of Orion (external site)

For other details of photographic exposure, search technical table by UKS reference number.

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Updated by David Malin, 2010, July 25