Anyways, I have question relating to the material of a Planet's physics. I have the formula to find the orbit of an object (mainly a comet), given an x,y position and an x,y velocity.

x acceleration = -GMx/r^3
y acceleration = -GMy/r^3

where G is Newton's Gravitational Constant, M is the mass of the Sun (which I'm not too sure of), x, y is the position of the planet, and r is the distance from the object to the sun.

However, I'm not sure where to find the x, y position and velocity of a planet so I can use the formula above.

I am actually trying to simulate the orbit of the planets using Direct3D, and can't find a way to calculate the orbits. Any help would be appreciated.

Thanks very much,