# Orbit of a planet

Can a planet move around a star in an exact circle? Does Kepler's laws prevent this from happening. Answers with mathematical base will be accepted.

• There are no "exact" circles in nature. Can an orbit be essentially circular? Yes. – CuriousOne Jan 23 '16 at 3:49
• @CuriousOne In classical mechanics there are exact circles, just like there are exact ellipse, taking a circle being as an infinite sided regular polygon. Why isn't any of the planet's in our SS not having circular paths? What are the requirements for a circular path? Can you put it mathematically into an answer? – N.S.JOHN Jan 23 '16 at 3:55
• – Anubhav Goel Jan 23 '16 at 3:58
• Classical mechanics is an approximate mathematical description of nature, it's not nature. You were asking if planets can move around stars in exact circles and the answer to that is no, real planets moving around real stars can't do that. There are always other masses that tug on their orbits and circular orbits are singular elements out of a continuously parametrized set of orbits, so hitting just the right combination of orbital energy and angular momentum is practically not possible. I know that is not what you are asking, but we have enough confusion between theory and reality, already. – CuriousOne Jan 23 '16 at 4:00
• Even in classical mechanics there are only exact circles in the strict two-body case. The universe has more objects than that. Draw your own conclusions. – dmckee --- ex-moderator kitten Jan 23 '16 at 4:07