what is a nebula composed of
A fine example of an emission nebula is the Orion Nebula (M42). Reflection Nebula-A reflection nebula differs from an emission nebula in does not emit radiation of its own. It is a cloud of dust and gas that reflects the light energy from a nearby star or group of stars.Reflection nebulae are frequently the sites of star formation.hese colors are the result of different elements within the nebula. Most nebulae are composed of about 90% hydrogen, 10% helium, and 0.1% heavy elements such as carbon, nitrogen, magnesium, potassium, calcium, iron.