Here's why:
* Nuclear Fusion: Stars generate energy through nuclear fusion, where hydrogen atoms fuse together to form helium. This process releases tremendous amounts of energy.
* Core Hydrogen Burning: The core of a star is the hottest and densest region, where fusion occurs most rapidly. As the star burns hydrogen, it slowly converts it into helium.
* Main Sequence Lifetime: The time it takes a star to exhaust its core hydrogen is its main sequence lifetime. This lifetime is determined by the star's mass. More massive stars have shorter main sequence lifetimes because they fuse hydrogen much faster.
* Sun's Main Sequence: Our sun is a relatively average star. Its main sequence lifetime is approximately 10 billion years.
After the sun exhausts its core hydrogen, it will enter a new stage of evolution, becoming a red giant and eventually a white dwarf.
