Thread: Gravitation - Find eccentricity of new orbit?

A planet is in a circular orbit about a massive star. The star undergoes a spherically symmetric explosion in which one per cent of its mass is suddenly ejected to a distance well beyond that of the planet's orbit. Find the eccentricity of the new orbit of the planet assuming that the planet is unaffected by the explosion.

Answer:

Spoiler:

Any ideas regarding how to do it?

Conservation of angular momentum.