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The Horsehead nebula in Orion

Date created: 1980-01-22

Tags: nebula, emission, Orion, Horsehead, dust


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 here, at the top of the picture, and is at about the same distance from the Sun as the nebula. On the left is the brilliant star 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 lanes within it, while other nebulae simply reflect the light of embedded hot stars and appear blue. The brightest of these is NGC 2023, close to the base of the horsehead shape, and within it are signs of star formation. All the nebulous objects and the dark cloud of dust that hides distant stars are about 1350 light years away.

Photograph made from UKST plates taken in October 1979.
Image width is about 100 arc min

Credit: David Malin

© Australian Astronomical Observatory