B Celestial Mechanics: Eccentricity of Orbits

[madison bond]

a simple question about celestial mechanics...will the orbit of an object in an eccentric orbit become more circular over time, irrespective of impacts with other debris?

 

[pixel]

No. An eccentric orbit is a stable solution to the equations of motion in a central force field.

 

[jim mcnamara]

@pixel - Consider:
The Earth's orbit varies over time in eccentricity from close to circular to mildly elliptic. Maybe that is what Madison Bond is referring to.

 

[Buzz Bloom]

Hi madison:

What causes the eccentricity of an orbit (of a small mass object about a large mass object) to change is the lack of spherical symmetry in the larger mass object. The changes in the eccentricity of the moon's orbit is mostly due to the non-spherical symmetry of the Earth's gravitational field.

Regards,
Buzz

 

[Janus]

a simple question about celestial mechanics...will the orbit of an object in an eccentric orbit become more circular over time, irrespective of impacts with other debris?

There is an effect called tidal circularization, in which tidal effects between the primary and the satellite work to reduce the eccentricity of the satellite. The strength of this depends on the proximity of the satellite and the mass of the primary. Jupiter has quite a strong effect on its inner satellites, and they have very small eccentricities. It is the gravitational interaction between the Moons themselves which prevent them from settling into circles.

 

[pixel]

@pixel - Consider:
The Earth's orbit varies over time in eccentricity from close to circular to mildly elliptic. Maybe that is what Madison Bond is referring to.

I was thinking of the ideal case of a particle in an inverse square force field.

 

[rumborak]

I think @pixel answered the OP question correctly, as I get the impression that OP thinks that elliptical orbits are naturally decaying towards a circular one, whereas Kepler showed that they are stable.