101 Must-See Cosmic Objects: M78

Wonderfully mysterious, M78 is the brightest swath of nebulosity in a group of specterlike glows some 2½° northeast of Alnitak (Zeta [ζ] Orionis), the eastern star in Orion’s Belt. Pierre Méchain discovered M78 in early 1780 and wrote to Charles Messier that the nebula surrounded two “fairly bright nuclei.” These nuclei are two 10th-magnitude stars (HD 38563A and HD 38563B), and the chief illuminators of the surrounding nebulae. While the ultraviolet radi