* Hydrogen Fusion: Stars generate energy through a process called nuclear fusion. The primary fuel for this process is hydrogen. Inside the star's core, the immense pressure and heat force hydrogen atoms to fuse together, forming helium and releasing a tremendous amount of energy.
* Main Sequence: This hydrogen-burning phase is known as the main sequence stage of a star's life cycle. The majority of a star's life is spent in this stage.
* Beyond Hydrogen: Eventually, the hydrogen fuel in the core will be depleted. The star then enters a later stage of its life, where it may begin to burn heavier elements like helium. However, hydrogen burning is the defining process of a star's main sequence existence.
So, to summarize:
* All stars burn hydrogen during their main sequence phase.
* This is the primary energy source for stars.
* The hydrogen burning process is what gives stars their brightness and stability.
