The Flame Nebula (NGC 2024; Sh2-227)
and Horsehead Nebula (IC 434; B33) are part of the Orion Molecular
Cloud. They lay approximately 1500 light years away.
The Flame Nebula consists of ionized
Hydrogen that is caused by the extreme ultraviolet light emitted
by the bright star Alnitak. This is the easternmost star in Orion's
belt. Dust lanes in front of the nebula give it its characteristic
The Horsehead Nebula is a dark nebula.
It is simply a cloud of dust that is visible due to its obstruction
of the background glow.
The blue reflection nebula to the
lower left of the Horsehead is designated as NGC 2023.