This feat seems to be a common feat in fiction with stars such as neutron stars or created or destroyed so so I made a calculation.
Gravitational Binding Energy Equation for stars is (3*G*M^2)/(r(5-n))
The average neutron star is 1.4 Solar Masses with a radius of 10 kilometers as stated here and there.
- Solar mass is 1.989 × 10^30 kilograms
- Mass of the average star is (1.4*1.989 × 10^30) kilograms
- Radius is 10000 meters.
- Assuming a n (which can go from 0.5 to 1) is 0.5
- G is a constant of 6.67408x10^-11
Calculation
- (3*6.67408*10^-11*((1.4*1.989 * 10^30))^2)/((5-0.5)*10000) = 3.4 × 1046 Joules (Solar System Level)
Calculator: http://apfloat.appspot.com/