Final answer:
During a star's main sequence phase, it produces about the same amount of energy as it radiates into space. Stars on the main sequence maintain equilibrium by generating energy through nuclear fusion in their cores.
Step-by-step explanation:
During a star's main sequence phase of its life, it produces about the same amount of energy as it radiates into space. Stable stars like our Sun maintain equilibrium by generating energy through nuclear fusion in their cores. This fusion process converts hydrogen to helium and is the main source of energy for stars on the main sequence. The main-sequence phase is a prolonged stage in a star's life where it remains relatively stable in size and energy production until it eventually exhausts its hydrogen fuel.