Barnard's loop nebula. True-colour optical image of a portion of Barnard's Loop (pink), an elliptical ring of glowing nebulosity surrounding the constellation Orion. This is the easternmost, and brightest, part of the loop, which was discovered by the American astronomer E. E. Barnard in 1895. It formed as the hot stars of Orion caught nearby gas and dust in a pressure wave, forcing them into an expanding ring. It is thought to have been expanding for around 3 million years. This image was produced by digitally combining photographs taken by the UK Schmidt Telescope in blue and red light.