Emission Nebulae Emission nebulae are clouds of high temperature gas.
Emission nebulae are usually the sites of recent and ongoing star formation.
The gas and dust in the nebula emits light because it is irradiated by nearby emerging stars. Located at a distance of about 1,600 light years, the Orion nebula is the brightest diffuse nebula in the sky, visible to the naked eye. It is the main part of a much larger cloud of gas and dust which extends over 10 degrees well over half the constellation Orion. Images 1 and 2 are 10s true-colour images using BVR imaging on the WHT prime focus camera. The New WHT Mosaic Camera - ING Newsletter article .