What is the orbital period of a cometary nucleus in the Oort Cloud???
If the orbit is circular (it stays far from the sun) and its radius is 100 astronomical units, the period is 1000 years and the orbital speed is 2980 meters per second. If the orbit is circular and its radius is 10000 astronomical units, the period is one million years and the orbital speed is 298 meters per second. The period of an orbit, expressed in units of Earth’s year, is equal to the semimajor axis of the orbit, expressed in astronomical units, raised to the power of 3/2. P = a^(3/2) The “semimajor axis” of a circular orbit is its radius. The orbital speed in a circular orbit is equal to v = 2 pi R / P where you would convert R from astronomical units to meters and convert P to seconds. You can also get the circular orbit speed like this: v = [ GM / r ]^(1/2) where GM = 1.32712440018E+20 m^3 sec^-2 The speed of an object in an elliptical orbit is given by the Vis Viva equation.
