Orion's Belt. Optical image of the three bright stars making up Orion's Belt in the constellation of Orion. North is at top. Forming a straight line from upper right to lower left, the stars are: Mintaka (Delta Orionis), Alnilam (Epsilon Orionis) and Alnitak (Zeta Orionis). There are two bright emission nebulae (red) near Alnitak at lower left. The Flame Nebula (NGC 2024, pink, left of Altinak) is bisected by a dark lane of dust. Below Altinak is the Horsehead Nebula (Barnard 33), a lane of dark dust extending over the emission nebula IC 434 (red). The red glows are due to the ionisation of hydrogen by radiation from nearby stars.