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Why do Nebulae exist?

A nebula (plural: nebulae) is an interstellar cloud of dust, hydrogen, helium, and other ionized gases. The word nebula was originally used to describe any diffused astronomical object, including other galaxies farther than the Milky Way. The most known one is the Orion Nebula.
The dust and gases in a nebula are scattered, but due to gravity the dust and gases form clumps. As the size of the clumps increases, the gravity becomes stronger and stronger. Once it reaches a certain size, the clumps collapse from their gravity. Due to the collapse, the material at the center of the cloud heats up and this is the beginning of a star.
When the collapse takes place, fragments of collapsing gas radiates energy gained by the release of gravitational potential energy. The fragments soon become opaque, which causes the temperature to rise.
As the required temperature is reached, the gases present start to glow. Later a nuclear reaction takes place due to the pressure and temperature of the gases and forms a star. Without nebulae, stars would not exist in the sky.




Credits: Harini

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