Cone nebula and Christmas Tree Cluster (NGC 2264). The cone neubula is the dark pointed patch in the yellow area at centre. NGC 2264 is an emission nebula, a huge cloud of gas and dust that glows as the hydrogen it contains is ionised by radiation from the hot young stars that have formed within it. This area lies 2600 light years from Earth in the constellation Monoceros. Different colours represent different ionised gases; sulphur is red, hydrogen is green and oxygen is blue.