The key element necessary for the formation of stars is hydrogen. In the stellar nebula, hydrogen gas accumulates under the force of gravity, leading to increased pressure and temperature. When the core reaches a critical temperature (around 10 million Kelvin), nuclear fusion ignites, converting hydrogen into helium and releasing vast amounts of energy. This process not only generates light and heat, making stars visible, but also drives the subsequent creation of heavier elements through stellar nucleosynthesis. Thus, hydrogen is essential for both the birth and lifecycle of stars, playing a fundamental role in the evolution of the universe.