Orion Nebula (M42,NGC 1976). An emission nebula in the constellation of Orion,M42 contains 4 bright young stars,less than 100,000 years old,known as the Trapezium. Ultraviolet radiation from these ionises hydrogen gas in the nebula,which then emits the red light seen,hence the name 'emission nebula'. A nebula is a cloud of gas and dust in space,many light years across. It contains materials to form new stars and planets,such as these Trapezium stars. The Orion nebula has the highest surface brightness of any nebula |