How does a nebula become a star?

Stellar formation is the process by which a nebula turns into a star. It mostly happens in areas with high interstellar density. The formation process is started by the gravitational collapse of a molecular cloud inside the nebula. The cloud collapses, breaking up into smaller areas and eventually forming a protostar. The protostar keeps accumulating material from the surrounding cloud, gradually gaining mass and temperature. When the protostar's core temperature reaches a certain point, nuclear fusion reactions begin, marking the beginning of the star's main sequence phase.

A nebula becomes a star through the process of stellar formation, which involves gravitational collapse and subsequent nuclear fusion. Initially, a nebula is a cloud of gas and dust in space, primarily composed of hydrogen and helium. Under the influence of gravity, regions within the nebula begin to condense and contract, leading to an increase in density and temperature.

As the gravitational collapse continues, the central region of the nebula, known as the protostar, becomes increasingly dense and hot. Eventually, the temperature and pressure at the core of the protostar become sufficient to initiate nuclear fusion reactions. Hydrogen atoms fuse together to form helium, releasing a tremendous amount of energy in the form of light and heat.

Once nuclear fusion begins, the protostar enters the main sequence phase of its evolution, where it steadily burns hydrogen fuel to sustain its energy output. This marks the birth of a new star. Throughout its main sequence phase, the star remains stable, balancing the inward pull of gravity with the outward pressure generated by nuclear fusion reactions.

The duration of a star's main sequence phase depends on its mass, with more massive stars burning through their fuel more quickly than lower-mass stars. Eventually, when a star exhausts its hydrogen fuel supply in the core, it undergoes further evolutionary stages depending on its mass. This can include expansion into a red giant, shedding its outer layers to form a planetary nebula, and eventually cooling and fading as a white dwarf, or undergoing a supernova explosion in the case of more massive stars.

In summary, a nebula becomes a star through the process of gravitational collapse, leading to the formation of a protostar and subsequent initiation of nuclear fusion reactions in its core. This marks the beginning of the star's life cycle, during which it shines steadily as a main sequence star before undergoing further evolutionary stages based on its mass.