Answer:
The angular momentum is same as it was before.
The rotation period is
times the original period.
The rotational kinetic energy is 9452 times greater.
Explanation:
The angular momentum
of a rigid body is
,
where
is the moment of inertia and
is the angular velocity.
Now, the law of conservation of momentum demands that
,
in words this means the angular momentum before must equal the angular momentum after.
Let us call
the mass,
the radius, and
the angular velocity of the sun before it becomes a white dwarf, then its linear momentum is
(Remember for a solid sphere
)
After it has become a white dwarf, the suns mass is 80% of what it had before <em>(went off by 20%),</em> and its radius has become 0.0115% its initial value <em>(8000 km is 0.0115% of the radius of the sun ); </em>therefore, the angular momentum is

which must be equal to the angular momentum it had before; therefore

which we solve for
:





which is about whopping 9500 times larger than initial angular velocity!!
Now the rotation period
is


since 

Similarly, the rotation kinetic energy will be


![K_2 =0.8*0.0115^2*9452^2 [\dfrac{1}{2}*\dfrac{2}{5} mR^2w_1^2]](https://tex.z-dn.net/?f=K_2%20%3D0.8%2A0.0115%5E2%2A9452%5E2%20%5B%5Cdfrac%7B1%7D%7B2%7D%2A%5Cdfrac%7B2%7D%7B5%7D%20mR%5E2w_1%5E2%5D)

which is about 9500 times larger than initial rotational kinetic energy!