M43
De Mairan's Nebula
Properties
Position & Identifiers
Visibility
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About M43
Description
De Mairan's Nebula is a bright emission/reflection nebula in Orion, physically part of the Great Orion Nebula complex but visually separated from M42 by a dark dust lane. It lies about 1,600 light-years from Earth and spans roughly 7 light-years. The nebula is illuminated by the young B-type star NU Orionis (HD 37061) at its center.
Observing Tips
Located immediately north of M42, separated by a dark lane of dust. Visible in the same field of view as M42 in any telescope. It appears as a bright, comma-shaped or round nebula with the central star clearly visible. Often overlooked by observers dazzled by the overwhelming splendor of M42 just below it. A UHC or OIII filter enhances the nebulosity. Best observed from November through March alongside M42.
History
Discovered by Jean-Jacques Dortous de Mairan before 1731, hence the name De Mairan's Nebula. Charles Messier cataloged it on March 4, 1769. It was initially described as part of M42 before being recognized as a distinct, though connected, region.
Fun Facts
Although M43 appears to be a separate nebula from M42, they are actually parts of the same enormous molecular cloud complex. The dark dust lane separating them is merely a foreground feature. The central star NU Orionis is carving a bubble in the surrounding gas, giving M43 its distinctive round shape — a miniature version of what the Trapezium stars are doing in M42.
Community Photos (1)
Credit: Ole Nielsen. License: CC BY-SA 2.5. (Wikimedia Commons)
Skybred Feb 28, 2026