1. The problem statement, all variables and given/known data When a star like our Sun no longer has any hydrogen or helium "fuel" for thermonuclear reactions in its core, it can collapse and become a white dwarf star. Often the star will "blow off" its outer layers and lose some mass before it collapses into the rapidly spinning, dense white dwarf. Suppose a star with mass 1.0 Msun, with a radius of 6.96×10^8 m and rotating once every 25 days, becomes a white dwarf with a mass of 0.62 Msun and a rotation period of 131 s. 2. Relevant equations Msun = 1.99 × 1030 kilograms M1 = 1.0 Msun R1 = 6.96 * 108 T1 = 25 days = 2 160 000 seconds M2 = 0.62 Msun R2 = ? T2 = 131 seconds T = 2 pi r / v = 2 pi r / w r = 2 pi / w .:. w = 2 pi / T I = (2/5)MR2 3. The attempt at a solution I1 x w1 = I2 x w2 (2/5)(M1 x R12)(2 pi / T1) = (2/5)(M2 x R22)(2 pi / T2) (M1 x R12)(1 / T1) = (M2 x R22)(1 / T2) (M1 / M2)(T2 / T1)(R12) = R22 sqrt((M1 / M2)(T2 / T1)(R12)) = R22 R2 = sqrt((1.99*1030)/[(0.62)(1.99*1030)](131/2160000)(6.96*108)2 = 6.88*106 m Checking the result by plugging into equations shows that I am roughly correct. But Mastering Psychics says I am wrong. Where is the mistake?