Here's why:
* Main Sequence: This is the longest and most stable stage of a star's life. During this stage, the star fuses hydrogen into helium in its core, generating the energy that makes it shine.
* Nuclear Fusion: The process of nuclear fusion is what powers stars. The main sequence stage is defined by the ongoing fusion of hydrogen.
* Other Stages: The stages before and after the main sequence (like protostar, red giant, etc.) are relatively short compared to the main sequence phase.
Example:
* Our Sun is about halfway through its main sequence stage, which is expected to last approximately 10 billion years. The remaining stages (red giant, white dwarf) will be significantly shorter.
Therefore, it's accurate to say that stars spend the vast majority of their lifespan as main-sequence stars.
