The Calc (WIP)
All the basic information has been covered above.
Using that information, the explosion yield is 4420000 megatons . The blast is only 50% of the energy, so 4420000(0.5) = 2210000 megatons.
This equates to 2.21 teratons, Low 6-B
Note: I wouldn't have to chop half the energy off if it was a nuke, but I don't know what it is so I just used the above values.
Apparently, the gravity is 960x Earth's.
Finding the gravity
a = GM/r
gravitational acceleration (a)
radius from the planet center (r)
planet mass (M)
G is the universal gravitational constant
a = G(4.8e27kg)/5850km
a = 9358.8954635108 m/s²
9358.8954635108 / 9.807 = 954.3x Earth's gravity
Finding the density
From Newton's gravitational law:
D = m/v
D = 4.8e27kg/4π(5850km)³
D = 1.908×10^6 kg/m³
Inlcuding the gravity, 2.24tT(954.3²) = 2.036 exatons, High 6-A