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thesaruman
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Homework Statement
A planet is in a circular orbit about a star that explodes, shedding 2% of its mass in an expanding spherical shell. Find the eccentricity of the new orbit of the planet, which otherwise is not affected by the shell.
Homework Equations
\sqrt{1-\varepsilon^2} = \frac{b}{a}, where b and a are the minor and major half-axis, and \varepsilon is the eccentricity; \rho (1 + \varepsilon \cos(\varphi)) = a(1-\varepsilon^2) (Kepler's orbit); A = \frac{L \tau}{2 m} (area law), where A is the area of the orbit, L is the angular momentum of the system, and \tau is the period of it.
The Attempt at a Solution
I have a bold hypothesis: the constant of the problem is the planet. If I it would be possible to change the coordinate system as centered on the planet, and if the Kepler's law keep inaltered, I could treat the star before and after the explosion as planets, and use the third law to stablish a relationship between their orbits. Is this possible?