| IC 434 | |
| Image Scale: | 1.3 |
| Type: | emission |
| Subtype: | H II region |
| Appmag V: | 4.5 |
IC 434 is a bright emission nebula in the equatorial constellation of Orion. It was discovered on February 1, 1786 by German-British astronomer William Herschel. The nebula is located at a distance of approximately from the Sun and spans the interior of a neutral hydrogen shell with an angular size of . At that distance, the dimensions correspond to a projected size of .
This is an H II region that is being ionized by ultraviolet radiation from the nearby Sigma Orionis (σ Ori) multi-star system. An additional half dozen stars provide further illumination of IC 434. This H II region is one of the youngest to form around members of the Orion OB1 association of hot stars. The region has a radius of about and a mass of around The mass displaced by the advancing ionization front of IC 434 is estimated at . The nebula includes dust with an estimated mass of .
IC 434 is surrounded by a shell of neutral hydrogen gas with the identifier GS206-17+13. The primary driving energy behind this expanding shell was likely supplied by the blue supergiant Epsilon Orionis. The Horsehead Nebula is a dark nebula that is silouetted against the diffuse background of IC 434. It is protruding from the Orion B molecular cloud, which is part of the Orion molecular cloud complex.