The Horsehead Nebula is the dark nebula in
front of the bright red emission nebula IC 434. Dark Nebulae are
clouds of dust in space that obscure the stars behind them.
Emission nebulae are clouds of glowing ionized gas. Reflection
nebulae do not shine by their own light, but are visible because
they reflect the light of nearby stars. Along with the Orion
Nebula, M42, it is part of a very large complex that is a
stellar nursery where stars are forming out of the dust and gas.
Located about 1,500 light years away, this complex is the
closest star forming region to our own solar system. The Flame
Nebula, NGC 2024, is to the lower left of Alnitak, Zeta Orionis,
the easternmost star in the three distinctive stars in the
Hunter's belt of Orion, and the brightest star in this photo. To
the lower left of the Horsehead is the blue reflection nebula
NGC 2023. Other reflection nebulae in the photo are IC 435, IC
432 and IC 431.