The structure in the Horsehead Nebula in Orion
AAO image reference AAT 36b.    « Previous || Next »

The Horsehead Nebula in Orion, NGC 2023, Barnard 33, horsehead.jpg, barnard33.jpg
Top is W, left is N. Image width is about 10 arc min
Image and text © 1999-2010, Australian Astronomical Observatory, photograph by David Malin.

This curious dark nebula is one of the best-known images in astronomy, probably because of its chance likeness to a recognisable form. The horse-head shape is an extension of a large cloud of dust from the outer surface of a large molecular cloud. Close to the Horsehead nebula it is illuminated by sigma Orionis (off the top of the picture) which causes the hydrogen there to fluoresce, outlining the horse-head shape against the red emission nebula IC 434.

The 'neck' of the Horsehead is completely opaque at visible wavelengths, and is one of the nearest dark nebulae now known as 'elephant trunks'. The parts of the nebula that correspond to the mane and lower jaw are partly transparent, and here the red nebula is seen as a true red, rather than the magenta hue of the rest of the glowing gas. This is because the dust abosrbs the blue component of hydrogen's spectrum. All these objects are about 1350 light years distant in the constellation of Orion.

Related Images
AAT 36.   The Horsehead Nebula and NGC 2023 (landscape format, wide field)
AAT 36a. The Horsehead Nebula, wide field
UKS 1.    The Horsehead Nebula and NGC 2024 in Orion
UKS 1a.  The Horsehead Nebula and NGC 2024 in Orion
UKS 23.  Faint nebulosity near Orion and Horsehead Nebulae
Constellation of Orion (external site)

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Updated by David Malin, 2010, August 1