What happens after a nebula contracts its temperature increases to million k?

As a nebula contracts and its temperature increases to millions of Kelvin, it initiates nuclear fusion processes, primarily converting hydrogen into helium. This marks the birth of a new star, as the immense pressure and heat overcome gravitational forces, leading to the ignition of fusion reactions in the core. The newly formed star enters the main sequence phase of its life cycle, where it will spend the majority of its existence. Over time, the star will evolve and eventually exhaust its nuclear fuel, leading to further stages in its life, such as becoming a red giant or supernova, depending on its mass.