planetary orbit?

Question

if the planets move around he sun in ellipses, why do they move farther away from the sun at one side? does the sun have more mass at one side?

Answer 1

Velocity, in a very small nutshell.

Ok, the planet is going around the sun. Its motion is fueled by gravity and kinetic energy.

As it comes closer to the sun the gravitational forces increase so the energy increases and, because e does equal mc squared, its mass increases which increases its potential energy which can be translated into greater kinetic energy and a whole lot more speed.

This means that as a planet comes closer to the sun it moves faster and even closer to the sun. It then sling shots around the sun because it has way, way more than enough energy to escape the gravitational attraction between itself and the sun.

Because of all this extra energy it is moving as fast as it was away from the sun as it did toward it. The further away it gets from the sun the lesser the influence of gravity. Our planet both slows down and travels further away from the sun due to the increasing effects of other forces on it.

Our moon, other planets, asteroid belts, and, even, comets effect our planet's motion. The closer we get to the sun the more the sun's influence has over our planet. The path our planet has taken and the speed at which it is traveling are greater than the gravitational attraction and even large enough to translate that force into energy to travel faster and further. It is not enough to break the bond between our planet and the Sun and shoot out and away from the solar system but enough to gain enough energy when approaching the sun to get further away from it on the other side, so to speak.

As it moves away from the sun the planet's velocity reaches a sort of critical point at the opposite side of the ellipse. It's energy is not enough to escape the hold of gravity and it turns back toward the sun.

There are way better ways to explain this. I am simply not smart enough to be able to do so.

I hope I've helped in some teeny way and not confused you more!

Answer 2

As Kepler discovered and Newton demonstrated, planets orbit the Sun in ellipses, with the Sun located in one of the two focus of the ellipse. The focus are separated from the center of the ellipse, so the planet will sometimes be in a point more distant from the focus (Sun), point called aphelion, and sometimes in the point closest to the focus (Sun), called perihelion.

A circle is a particular case of ellipse. In that case both foci are coincident with the center of the circle. In fact, planetary orbits are close to circles.

This has nothing to do with mass assimetry of the Sun. It is a consequence of the Newton gravitation law.

For more info, please take a look at
http://en.wikipedia.org/wiki/Orbit

Answer 3

They could orbit in a perfect circle but most travel in ellipses.
To compensate for the difference in gravity at different distances the planet speeds up or slows down..
A higher orbit requires less speed a lower one more speed the varying speed of an ellipse splits the difference.