rotation of planets

Hi,
I was wondering why there is so little information about rotation of
planets. One of my friends asked me this interesting question.

Where did the rotational motion for the planets originate from?
As far as I can think, it could be the sum of angular momentum
gathered by the constituents during their formation

I would be happy to see some references to the subject.

Another corollary is, why all the planets are round? Do irregular
objects with uneven torques on the surface area due to rotation will
eventually become round are some of the things that came to my mind.

Also, is there anything like gyroscopic stability that is necessary to
keep them in orbit.

In article ,
Ravi wrote:
Hi,
I was wondering why there is so little information about rotation of
planets. One of my friends asked me this interesting question.

Where did the rotational motion for the planets originate from?
As far as I can think, it could be the sum of angular momentum
gathered by the constituents during their formation

Precisely! And the chance of the sum of the angular momentum being
exactly zero is quite small. Therefore almost every celestial body has
a rotation.

I would be happy to see some references to the subject.

Another corollary is, why all the planets are round?

Because of gravity. However the celestial body must be large enough
for this to have an effect. Therefore, small asteroids are frequently
irregular in shape.

Do irregular objects with uneven torques on the surface area due to
rotation will eventually become round are some of the things that came
to my mind.

Suppose the Earth had a mountain some 1000 times taller than Mount Everest.
What would happen to it? It would collapse under its own weight!

A spherical shape is the equilibrium shape for a large body subjected
to its own gravity. If the body rotates, the equilibrium shape changes
to a spheroid instead - a spheroid is an ellipsoid with two of its
three principial axes equally large.

Also, is there anything like gyroscopic stability that is necessary to
keep them in orbit.

Nope! Gravity combined with inertia is enough.


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