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**1. Homework Statement**

(Assuming all circular orbits)

(Assuming all circular orbits)

Say there is a star with mass M and a planet orbiting that star with a mass m.

The star M then suddenly loses half of its mass. (So now it is M/2)

What is the new radius of orbit of the planet around the star? Warning: Velocity will not be the same!

I'm not sure how to tackle this problem. I know for sure it has to do with angular momentum

**2. Homework Equations**

L=Iω or r x p angular momentum

**3. The Attempt at a Solution**

conservation of momentum for the planet

from Iωi = Iωf, I got m r

_{i}v

_{i}= m r

_{f}v

_{f}, but that doesn't really help