1. The problem statement, all variables and given/known data Assume the Sun is a uniform, rigid sphere (it is spherically shaped but actually is not of uniform density nor a rigid body). The Sun rotates once every 27 days. (a) Calculate the rotational kinetic energy of the Sun in joules. (b) The luminosity (power output) of the Sun is 3.826 x 1026 W, a rather powerful light bulb! For how many years could the Sun shine at its present luminosity if it were radiating away its rotational kinetic energy? [The energy source of the Sun is not the rotational kinetic energy but rather the nuclear fusion of hydrogen nuclei, creating helium.] 2. Relevant equations T=2(Pi)r/v KErot=0.5Icenter of mass*angular velocity2 Icenter of mass= 2/5Mr2 for a solid sphere about any diameter Angular Velocity= 3. The attempt at a solution I'm having trouble with so few numbers. I googled the mass of the sun and got 1.98892e30 kilograms and the radius of the sun = 695 500 000 meters T=2(Pi)r/v v/r= 2pi/T T=27days=2332800s v/r=2.6934e-6 KErot=(1/2)(2/5)mr2(v/r)2 KE=(.2)M of Sun (r of sun)2 (2.6934e-6) KE=.2(1.98891e30)(6.95e8)2(2.6934e-6)2 KE=1.39385e36 I double checked my math, and this is the right answer! :) I have no idea how to do part B though.