Final answer:
The Sun produces energy through nuclear fusion, which involves the combination of hydrogen atoms to form helium. The Sun's lifetime is determined by the amount of fuel it has for fusion reactions. It will continue to shine for about another 5 billion years before undergoing changes.
Step-by-step explanation:
The Sun produces its energy through a process called nuclear fusion. In the core of the Sun, hydrogen atoms combine to form helium, releasing a tremendous amount of energy in the process. This energy is in the form of light and heat, and it is what makes the Sun shine.
The lifetime of the Sun is determined by the amount of fuel it has for nuclear fusion. The Sun has enough hydrogen to continue fusion reactions for about another 5 billion years. As the Sun burns through its hydrogen fuel, it will eventually exhaust it and begin fusing helium. At that point, the Sun will start to expand into a red giant and eventually shed its outer layers, becoming a white dwarf.