Orion Nebula, also know as Messier 42, is a diffuse nebula situated in the Milky Way. A diffuse nebula is a cloud of interstellar material, widespread heaps of gas and dust. If they are massive enough, then they lead to the formation of stars. The Orion nebula is the nearest “star factory” and is visible to the naked eye. It is located at a distance of 1,344 ± 20 light years from Earth. It is 24 light years across and 2000 times the mass of the Sun. It is one of the most photographed objects in the night skies. It can be easily seen through binoculars and small telescopes.
Observations of this nebula have shown about 700 stars in various stages of their formation. Stars form when clumps of Hydrogen and other gases in an H II region contract under their own gravity. An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. As the gas collapses, the central clump grows stronger and the gas is heated to extreme temperatures by converting gravitational potential energy to thermal energy. If the temperature gets high enough, nuclear fusion will ignite and form a protostar. The protostar is ‘born’ when it begins to emit enough radiative energy to balance out its gravity and halt the gravitational collapse. Once the protostar enters into its main sequence phase, it is classified as a star.