The word ‘nebulae’ is derived from the Latin word for ‘clouds’. Indeed ,a nebula is a cosmic cloud of gas and dust floating in space. More than one Nebula is called nebulae. Nebulae are the basic building blocks of universe. They contain the elements from which stars and solar systems are built. Stars inside these clouds of gas cause them to glow with beautiful reds, blues, and greens. These 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. These clouds of matter are also quite large. In fact they are among the largest objects in the galaxy. Many of them are the dozens or even hundreds of light years across. Nebulae are divided into five major categories. These are emission nebulae, reflection nebulae, dark nebulae, planetary nebulae, and super nova remnants. Emission and reflection nebulae tend to be fuzzy in appearance and lack any noticeable shape or structure. They are also known as diffuse nebulae.
