'''Main sequence''' is the stable phase of a star's lifetime, when outward pressure from internal fusion process using hydrogen for fuel is balanced by the inward force of self-gravitation. This phase is usually the longest phase of a star's lifetime. | '''Main sequence''' is the stable phase of a star's lifetime, when outward pressure from internal fusion process using hydrogen for fuel is balanced by the inward force of self-gravitation. This phase is usually the longest phase of a star's lifetime. |