An interesting phenomenon is that presence of reflection nebula means the presence of an emission nebula somewhere close.ġ0. Reflection nebulae appear blue in color.ĩ. They only reflect the light from the nearby stars. They are so named because they do not emit their own light. Apart from emission nebulae we have other types of nebulae known as the reflection nebulae. The Orion constellation that we see has an emission nebula known as Orion nebula.Ĩ. Emission nebulae are usually pink or red in color because of the sizzling hot particle rays, but they can have other colors.ħ. When a star forms inside a nebula, ultraviolet rays are emitted and the entire nebula is lit up, resulting in what is known as emission nebula. Eventually they become so hot that hydrogen present in them gets ignited and new stars comes to life. The denser they become, the hotter they get. We know that stars can form inside nebulae, but how? According to scientists, gas and dust inside these nebulae squash together under their own gravitational pull.Īs a result, the clouds start contracting and get denser. Some look like a horse head, some look like a crab, some like a butterfly and some look like cat’s eye!ĥ. We know that nebulae are ginormous but how do they look like? Nebulae have myriads of shapes. Nebulae are often referred to as star nurseries of the universe because stars often form inside the nebulae.Ĥ. So imagine how big a nebula can be that stretches hundreds of light years across!ģ. If our assumed circular nebula stretches only one light year across then, the diameter of the nebula will be 9,460,800,000,000 kilometers. So, the maximum distance between two extreme points of the nebula will be its diameter. Let us trivially assume that we have a nebula in form of a perfect circle (which usually never happens). Light covers a distance of 300,000 kilometers in a second.