For a uniform, spherical mass, the gravitational binding energy is
Where G is the gravitational constant, M is the mass of the sphere, and r is the radius of the sphere.
Assuming that Earth is uniform (which is not correct, but is close enough to get an orderofmagnitude estimate) with M = 5.97×10^{24}kg and r = 6.37×10^{6}m, U is 2.24×10^{32}J. This is roughly equal to one week of the Sun's total energy output.
According to the Virial theorem, the gravitational binding energy of a star is 2 times its internal thermal energy.
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