Answer the following question.
How do stars form?
Spaces between the stars present in a galaxy are occupied by huge clouds of gas and dust, known as interstellar clouds. Contractions happen in this cloud due to some natural disturbance. Because of this, the density and temperature in the cloud starts increasing and a dense sphere of hot gas is formed from the cloud. Nuclear energy (energy released due to fusion of atomic nuclei) is generated with the burning of fuel, like hydrogen and helium, in the sphere when it attains a sufficient amount of density and temperature at its centre. Due to this energy generation, the gas sphere becomes self luminous and thus a new star is formed.