Orion constellation. Optical image of the lower part of the constellation Orion, the hunter. North is at top. The Orion Nebula (M42) is the pink area at lower centre. It is a massive starbirth region which glows pink as the hydrogen gas within it is ionised by the radiation from hot young stars. Above M42 is Orion's Belt, formed of three stars in a line. From left to right these are Alnitak (Zeta Orionis), Alnilam (Epsilon Orionis) and Mintaka (Delta Orionis). Just left of Alnitak is the Flame Nebula (NGC 2024), and just below it is the Horsehead Nebula (B33 and IC 434). At bottom right is the blue supergiant star Rigel (Beta Orionis), the seventh brightest star in the sky.