Photograph of the Horsehead Nebula, just discernible as a dark shadow in the centre of the picture. Also known as Barnard 33, the Horsehead Nebula is located in the constellation of Orion and is approximately 1500 light years from Earth. The nebula was first discovered in 1888 when it was noticed on a photographic plate taken at the Harvard College Observatory in the United States. The distinctive horsehead shape is a thick opaque cloud of dust and gas, protruding from a larger cloud, and is silhouetted against light coming from the emision nebula IC 434 which lies behind it.
© Science Museum / Science & Society Picture Library