Question

The star Tau Ceti's mass is 1.6 ✕ 10³⁰ kg, its radius is 5.5 ✕ 10⁵ km, and it has a rotational period of approximately 34 days. If Tau Ceti should collapse into a white dwarf of radius 9.7 ✕ 10³ km, what would its period (in s) be if no mass were ejected and a sphere of uniform density can model Tau Ceti both before and after?

_______ s

Answer 1

Since no external torque acts on the star, its angular momentum remains conserved.

Now, time period is given as

Thus,

and