Nebulae are clouds of gas and dust occurring in space. They are very large, ranging in size from millions of miles across to hundreds of light-years across. Called the nurseries of the universe, nebulae are the sites where stars and planets are born and where they die.
Emission nebulae are the birth site of a star. They emit very hot particles that appear as bright rays of light. Filled with an abundance of hydrogen gas, an emission nebula glows red or pink. The Orion Nebula, found in the Orion constellation, is an emission nebula.
Reflection nebulae do not have the energy necessary to emit hot particles. The dust in this type of nebula reflects light from surrounding areas of energy. They glow blue in color. The Witch Head nebula, also found in the Orion constellation, is an example of a reflection nebula.
Planetary nebulae resemble small planets when viewed through a telescope. They are not planets, but stars that have run out of fuel. As the star uses up its gas, the outer layers are blown off in a bubble shape creating the appearance of a globe. Before dying, the star expands into a giant red star consuming anything in its path before shrinking and pushing off the outer layers.