This mosaic image taken by NASA's Wide-field Infrared Survey Explorer features three nebulae that are part of the giant Orion Molecular Cloud. The image covers an area of the sky about three times as high and wide as the full moon (1.5 by 1.8 degrees). Included in this view are the Flame nebula, the Horsehead nebula and NGC 2023. Despite its name, there is no fire roaring in the Flame nebula. What makes this nebula shine is the bright blue star seen to the right of the central cloud, Alnitak. Wind and radiation from Alnitak blasts away electrons from the gas in the Flame nebula, causing it to become ionized and glow in visible light. The infrared glow seen by WISE is from dust warmed by Alnitak's radiation. Also known as NGC 2024 and Orion B, this nebula is classified as a molecular cloud. The famous Horsehead nebula appears in this image as a faint bump on the lower right side of the vertical dust ridge. It is classified as a dark nebula because the dense cloud blocks out the visible light of the glowing gas behind it. WISE's infrared detectors can peer into the cloud to see the glow of the dust itself. A third nebula, called NGC 2023, can be seen as a bright circle in the lower half of the image. NGC 2023 is classified as a reflection nebula, meaning that the dust is reflecting the visible light of nearby stars. Color in this image represents specific infrared wavelengths. Blue represents light emitted at 3.4-micron wavelengths, mainly from hot stars. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Green represents 4.6-micron light and red represents 12-micron light.