M78

Messier 78 (M78, NGC 2068) is the brightest diffuse reflection nebula in the sky, situated in the rich constellation Orion.

This object was discovered by Pierre Méchain in early 1780. Charles Messier added it to his catalog on December 17, 1780.

M78 belongs to the Orion complex, a large cloud of gas and dust centered on the Orion Nebula M42/M43, and is about 1,600 light years distant. It is the brightest portion of a vast dust cloud which includes NGC 2071 (northeast, lower right in our image), NGC 2067 (close northwest), and very faint NGC 2064 (southwest), all visible in the image. Together with some other nebulae, including NGC 2024 (Orion B) near Zeta Orionis (sometimes called the Flame Nebula), all these nebulae are associated with the molecular cloud LDN 1630 (from Lynds' Catalogue of Dark Nebula), a part of the Orion complex.

As a reflection nebula, M78 is a cloud of interstellar dust which shines in the reflected and scattered light of bright blue (early B-type) stars, among them the brightest, HD 38563A, and second-brightest HDE 38563B, both of about 10th visual apparent magnitude. The nature of M78 as a reflection nebula was discovered by Vesto M. Slipher of Lowell Observatory in 1919 (Slipher 1919), by the investigation of its spectrum: M78 exhibits a continuous spectrum, which resembles that of the bright stars enlightening it. At its distance, M78 measures almost 4 light years in extension.