Models of the sun indicate that only about 10% of the total hydrogen in the sun will participate in nuclear reactions, since it is only the hydrogen in the central regions that is at a high enough temperature. use the total energy radiated per second by the sun, 3.8 × 1026 watts, alongside the exercises and information given here to estimate the lifetime of the sun. (hint: make sure you keep track of the units: if the luminosity is the energy radiated per second, your answer will also be in seconds. you should convert the answer to something more meaningful, such as years.)