This started in another discussion where this was introduced as a side issue, and I provided the following answer. Others might prefer to discuss this. My previous answer was:
First, why is rotation usually prograde? In my ebook "Planetary Formation and Biogenesis" I outline a mechanism that involves essentially monarchic growth for the giants, and probably for other planets. The mechanism avoids the plethora of planetesimals because over 80 years nobody has a clue how they could form - I proposed that the initiation is chemical, and bodies have special zones that favour very rapid growth. In the absence of major collisions, what happens is the biggest body moves towards Keplerian velocity, which is faster than the gas stream. That leads to a greater pressure on the leading face, and as the gas is also falling starwards it applies a torque to the leading face that provides prograde spin. (What happens next also gives the body an increase in angular momentum, and hence lift.)
Uranus and Neptune are problems because they effectively state on their side and somewhat retrograde. Pluto's rotation is almost certainly affected by whatever formed its moon system - presumably a collision - and I assume something like that must have happened for the Ice Giants. The planets Mercury and Venus originated in zones where there would be more rocky bodies formed, and thy would be bombarded randomly so there would be little rotation. Mercury seems to have got itself into some sort of resonance with the sun. Venus has a retrograde rotation, and the most interesting explanation I have seen for that is that thermal tides in the atmosphere lead to that in planets inside the so-called habitable zone. What happens is the hottest part of the atmosphere is about 3 pm, and that leads to atmospheric currents that apply the retrograde torque. Venus is actually limited here because it has so much atmosphere and therefore so much thermal inertia. If it had a bit less it would rotate faster retrogradely - if that theory is correct.
Dear Ian,
You wrote :
(1) "First, why is rotation usually prograde? "
Prograde as well as retro-grade, both type of rotation exist in nature.... For example Venus,Uranus, Neptune ,Pluto and Iris rotates clockwise, whereas other planets rotates anticlockwise.. . I have No knowledge that how Kuiper belt rotates . Every planets in our solar system do revolves in only anticlockwise about the Sun.... Why only Anticlockwise ? I have No idea...... Answer that you have given seems very ad-hoc.. Do you know any mass in nature which does not rotates and revolves around singular points?
Dear Gokaran,
Clockwise is not very helpful - it depends on whether you are above or below. The concept of prograde rotation of the planet is that compared with its orbit around the sun, it behaves as if it is rolling. Retrograde is as if it were skidding with backspin. The direction of the orbits is because of the direction of rotation in the accretion disk, and is the same direction the star spins. Similarly, the plane of the rotation of the planet is usually thought to have started as in the plane of the orbital motion, however Uranus is actually almost at right angles (a few degrees retrograde) and this is a puzzle. Earth's plane of rotation is dislodged - presumably because of the collision that caused the Moon to form, but the plane of rotation can also change because of an asymmetry in mass distribution - Mars is believed to change its obliquity by ten of degrees from time to time because its mass is not spherically symmetric. If something crashed into Uranus very early in its formation, it may have tipped it - we do not know.
Dear Ian,
Yes, prograde motion is very common... The new 12 moon of Jupiter discovered in this year, seems some are revolving clockwise about Juipeter.. It is very surprised to me...I don' t know any system where planets or moon revolving clockwise..
As Ian said, anticlockwise as seen from the north pole is clockwise as seen from the south. The planets orbit around the Sun in the same direction that the Sun rotates because both formed out of the same nebula and inherited the direction of its angular momentum vector.
Planets generally rotate in the same direction for the same reason but can be disturbed through tidal locking, precession and close encounters or collisions. The Moon stabilises Earth's axis, Mars varies more, and the rotation of Venus and Uranus show the extremes possible.
It may be of interest that some star-burning planets orbit retrogradely. The reason is believed to be that they were formed at a normal position, gravitational interactions with another led to one being ejected outwards and the other put into a highly elliptical orbit, and if the eccentricity is high enough, tidal interactions with the star "flip" its direction and then circularize in the new orbit.
Thierry De Mees
Arguing that planets are formed from electromagnetic explosions from the star is not generally held. Further, if stellar magnetism is the driving force it should be weaker further from the star. Jupiter has a faster station than Earth. My case for what I argue is in the following ebook, which analyses over 600 scientific papers.
Planetary Formation and Biogenesis
http://www.amazon.com/dp/B007T0QE6I
You might be interested in this paper: "Prograde rotation of protoplanets by accretion of pebbles in a gaseous environment" by Anders Johansen and Pedro Lacerda, doi:10.1111/j.1365-2966.2010.16309.x
https://watermark.silverchair.com/mnras0404-0475.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAArkwggK1BgkqhkiG9w0BBwagggKmMIICogIBADCCApsGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMPgQaI1SXHgNQT4RPAgEQgIICbOp-ETlOaT34wW2w6CDbyDox3YZxekdq31ngYSnkPcLz4Vg3VzBB-vrKHqHZHbq93u1pxCgkemXTNB5g7gwgC7AzAcleKs0iDMP1I08xwNkYSXHBwK6Z_HxlHJ4cw5GVlImnggXYI4EDD4dkzp8zNOzqCF1H1z50k3PUFdVfC2xZ4jnNZefxw6czejhoK3fzZGRII7MjLgKxjTwI2R42lBi72YGrA7QaVqbf50Wqsm67Aav3Wq3vahzSiABcsdcghceRymRTF-q4f7r1_HSOYFHX5gzqlCMo2xBEBcgMJa2-o5ecADoOBP1w0vof-F36BkNUgpO4SsxXjjF-IdWnVnAhDSKaykz2ycSZdBR02rGdZ1RRp6ciFMAlfOnwV5jz3ohICyXkesGWLhKE5qNAuai3hR3Jm0Ok6VcbOvgeFCdykpDiVjzjlsmOsSfTCmWjrt4oIbtijCcijQGArOyTelbatXKqH_d7jgg0Ka28ZCvcj_4pJN51MECtFs1TfrYk8gf55HX-ts1MBHrYjPmeT2v4zueLG4Rzn6JorPoD3c0gTiqxWSuMddbJAJNkb_vW-9ZAPPP6fv2yWfuVx9r32-H5tLdtx6zRrtqe46zekkJKdP-ipxkgeMuo62o6LaL5A0Te7zxsPqrUYeWauY-yrIh2ncDaoUjkcXuTzA9WY4pK0raSQ5w0lLo1dbOn88rO4pkByb3_ZeeCVcYPTudawkfQ0GZJKG0YZmsqjcVcb36x1PGxB-zxaU_KfozQV5GW-1CEd3kn0SSh8r-VLJfZq0OnY5uBilJZ1jOVMjvqpD87kxnAGdNpWdCu8r_3
I think pebble accretion is a favored mechanism for the accretion of many full planets, too, based on this pdf which says it's by Alessandro Morbidelli of CNRS, Observatoire de la Cote d’Azur: "Accretion Processes": https://arxiv.org/pdf/1803.06708.pdf
The problem with pebble accretion is it has to be gentle as there is no mechanical strength until the object gets big enough to be gravitationally stable. If you look at small asteroids, their gravity is negligible, but they have craters which implied an impact with enough energy to melt silicates. Impacts could have quite high energies, and even moderate ones would scatter pebbles, like the result of a collision on a snooker table. The evidence is that the initial maximum sizes of the dust is about 4 μm. How does this form strong pebbles? I have nothing against pebbles, but there has to be something stronger holding them together, and mhy answer to that comes from chemistry. Chemistry, after all, is the the science of the interactions of matter, but astronomers and physicists seem strangely reluctant to consider it, probably because what is required for this problem is relatively obscure.
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