Cone and rosette nebulae. The cone neubula (NGC 2264) is the dark pointed patch in the yellow area at centre left. The rosette nebula is at upper right. These are emission nebulae, huge clouds of gas and dust that glow as the hydrogen they contain is ionised by radiation from the hot young stars that have formed within them. Both nebulae are in the constellation Monoceros. The cone nebula lies 2600 light years from Earth, the rosette nebula is 5000 light years from Earth. Different colours represent different ionised gases; sulphur is red, hydrogen is green and oxygen is blue.