Orion molecular cloud complex containing the Orion Nebula (M42, lower centre) and Horsehead Nebula (upper left). The Orion Nebula is a vast cloud of dust and gas where new stars are being formed. It is located around 1500 light years from Earth, in the constellation of Orion. The red colour of the nebulae is from the emission of ionised hydrogen from its excited state back to its ground state. The three stars that cross the top of the image diagonally are Alnitak, Alnilam and Mintak, the three main stars of Orion's belt. Photographed from the Cumeada Observatory in the Dark Sky Alqueva Reserve, Portugal.