0.0768 revolutions per day
Explanation:
R = Radius
= Angular velocity
As the mass is conserved the angular momentum is conserved
Moment of intertia for solid sphere
Moment of intertia for hollow sphere
Dividing the moment of inertia
From the first equation
The angular velocity, in revolutions per day, of the expanding supernova shell is 0.0768 revolutions per day