Why do the Planets in our Solar System Orbit the Sun Counter-Clockwise?

Question: The planets in our solar system are orbiting the Sun counter clockwise, why? Do the laws of physics dictate that all planet orbit their respective stars counter clockwise or is it possible to have a solar system where the planets are in a clockwise motion around their star?  – David

Answer: Most of the objects in our solar system, including the Sun, planets, and asteroids, all rotate counter-clockwise.  This is due to the initial conditions in the cloud of gas and dust from which our solar system formed.  As this gas and dust cloud began to collapse it also began to rotate.  That rotation just happened to be in a counter-clockwise direction.  There is nothing special about a counter-clockwise rotation, though.  We could easily have found ourselves living in a solar system which was rotating clockwise about our Sun, if that was the initial state of rotation of the gas and dust cloud from which our solar system formed.  Note, though, that there are two oddballs in our solar system that do not rotate in the same way as the rest of the planets.  Uranus rotates about an axis that is nearly parallel with its orbital plane (i.e. on its side), while Venus rotates about its axis in a clockwise direction.  These oddities are thought to be caused by events, such as collisions, which occurred during the formation of the solar system.

Jeff Mangum

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14 Responses to Why do the Planets in our Solar System Orbit the Sun Counter-Clockwise?

  1. Þorsteinn Sigurðsson says:

    I was just wandering whether the orbital direction of our planets and Sun could be dictated by our orbital direction around the galaxy, just as the rotation around our Sun seems to dictate the rotation of the planets.
    I have not managed to find any sources indicating this relationship between our solar system and our galaxy.

    Are you positive that orbital direction of our planets is the same as their rotation, counter clockwise? I’ve been scratching my head over this all night and find Internet sources to be confusing to say the least. They don’t agree on either the orbital direction of our planets or their rotation.
    The reason I ask is threefold:
    1. Because of angular momentum, matter in lower orbit around the Sun moves faster than matter in higher orbit. As matter condenses into planetary objects friction between the object and incoming matter would cause it to rotate in the opposite direction of its orbital direction.
    2. All planetary objects have been hammered by incoming asteroids, comets, and even other planets for billions of years. Majority of those impacts have been from objects in higher orbit around the Sun moving too slowly to maintain orbit. As they tend to hit planets on the outer side as they move in their orbit they should cause them to rotate, again in the opposite direction of their orbital direction.
    3. All planetary objects have a diameter and that diameter causes an orbital difference between the side that is closer to the Sun and the side that is further away from the Sun. The side that is further away from the Sun has a slightly longer orbit then the other. Condensed matter forming planetary objects will seek to move at the same speed, bound by gravity, and should seek to compensate this orbital difference by rotating, again in the opposite direction of it’s orbital direction. Actually I’ve been searching for sources that might tie this with rotational tendency of planets, but have found none. Perhaps this difference is too small to make an impact.

    Anyway, hope I’m not overwhelming you. Internet sources are just not helping 8;

    Þorsteinn Sigurðsson

    • Jeff Mangum says:

      Hello Porsteinn,

      Let me take your questions in order:

      Correlation Between Planetary Orbits and Solar System Orbit in our Galaxy: It is the original angular momentum which existed during the formation of an object, whether it be a planet, star, or galaxy, which dictates the initial angular momentum, and thus rotation speed and direction, of an object in the universe. Since the formation of our galaxy and the formation of our solar system were two separate events, their relative directions of rotation are not related. By coincidence, though, the rotation direction of the planets is the same as that of the Milky Way as viewed from above, counter-clockwise.

      Orbital and Rotational Directions for the Planets: With only two exceptions, Venus and Uranus, the orbital direction of the planets is the same as their rotational directions, counter-clockwise. Venus rotates on its axis in a clockwise direction, while Uranus has a rotational axis that is tilted by almost 90 degrees relative to the orbital plane of the planets.

      Planets naturally rotate in the same direction that they orbit due to the fact that a point on a planet that is closest to the Sun will orbit slightly faster than a point on that planet which is on the opposite side of the planet, furthest away from the Sun. As a point on the planet moves from the slower outward facing direction to the faster inward facing direction, it speeds up, while the opposite happens for points on the planet that move from the faster inward facing direction to the slower outward facing direction. This results a rotation direction that is in the same direction as the orbit of the planet. If you want to see a nice summary with diagrams that do a good job of explaining this see http://www.sjsu.edu/faculty/watkins/solarspin.htm.

      The effects of impacts on these rotational and orbital motions are in most cases not significant, with the possible exception of the “oddball” planets Venus and Uranus. Early in the formation of the Sun and planets the frequency of impacts was probably quite large, but as the planets formed those impacts became less frequent, and the relative size of those impacting bodies became smaller.

      Thanks for your comment and I hope that this answers your questions.

      Jeff Mangum

  2. Kreative says:

    So, this isn’t a technical question by any means, but how do we know that everything is orbiting counter-clockwise? Wouldn’t this observation be relative to which direction you were looking at the solar system from?

  3. Jeff Mangum says:

    Yes, the “direction” of rotation is relative to the orientation of the observer relative to the solar system. The orientation we normally use is relative to a vantage point above the plane of the solar system.

    Jeff Mangum

    • Alison Moodie says:

      What do you mean by “above”, Jeff? You are thinking as a ‘northern hemispherean’ ! If you view the SS from above the Earth’s south pole, then the Earth, the other planets and indeed the Sun (on its axis) rotate clockwise.

  4. Jeff Mangum says:

    Alison, I am using the normal convention that the North Pole is “up”.

    Jeff Mangum

    • Alison Moodie says:

      Ha ha! Normal for whom? Seriously, ask any Australian, Chilean or New Zealander and s/he will tell you that South is ‘up’.

      And with your ‘north up’ mindset, what policy would you adopt for rotating systems – such as our Galaxy – that have no ‘north’ pole?

  5. Jeff Mangum says:

    I am not aware of any convention for defining “up” or “down” on a galaxy-wide scale. We can measure the rotation direction and orientation with respect to our vantage point, but generally don’t try to assign an association to an “up” direction.

    Jeff Mangum

  6. Rick Thurman says:

    On the question of up and down: for Earth, since most of the landmass and therefore livable area is in the current magnetic North, I can see sticking with convention. In addition, I’ve also tried looking up Web sources on the Sun’s positional relation to the galaxy and am still trying to wrap my head around it. Feel free to correct me if I’m wrong, but it seems the Earth’s North Pole and Sun’s conventional North Pole are “leaning toward” our system’s direction of rotation around the galaxy’s center, roughly the black hole Sagittarius A*. If in fact Earth, Solar and the Milky Way all share the same direction of rotation (even if by historical accident ), then for our human centered purposes that could be sufficient reason to judge rotational North (as opposed to magnetic?) to be whatever axial direction that renders the direction of rotation to be counterclockwise, or “to the left”. Since angular momentum seems to be one of the most fundamental phenomena at astronomical scales, that would be an easily discernible property for establishing orientation conventions. My question at this point would be, do any of the star surveys or catalogs even try to regularly record, the axial orientation and direction of rotation for stars, and now exoplanets? I imagine this would be a question of interest with pulsars. If it has been surveyed and cataloged, are there any interesting patterns, such as similar directions among stars sharing the same birth cloud?

    • Jeff Mangum says:


      The final orientation of a planetary system’s rotational axis is dependent upon the dynamical collapse process that formed the star which hosts the planetary system. This dynamical collapse process is a local phenomenon, driven by the angular momentum properties of the dense gas cloud from which the star and planets formed. There is little connection between the orientation of the rotation axis of the Milky Way galaxy and the orientation of the rotation axis of a planetary system in the Milky Way. For example, the orientation of our solar system is almost perpendicular to the plane of the Milky Way galaxy. For a very thorough description of this fact and all of the other motions that contribute to the speed and direction of the Earth through the Universe, see Larry McNish’s excellent description of “How Fast Are We Moving?” at http://calgary.rasc.ca/howfast.htm.

      Jeff Mangum

  7. Jackson says:

    Hi Jeff,

    One of my students came across your blog and became confused by this statement:

    “Note, though, that there are two oddballs in our solar system that do not rotate in the same way as the rest of the planets. Uranus rotates about an axis that is nearly parallel with its orbital plane (i.e. on its side), while Venus rotates about its axis in a clockwise direction. ”

    In this portion of your answer, you use the word “rotation” fast and loose. In the first part of your answer, you are talking about how a planet travels relative to the Sun, in which you should be using the word “revolution.” In the quoted text above, you are talking about axial rotation, which is an entirely different concept.

    – Jackson

    • Jeff Mangum says:

      I agree that we often use overlapping terms for “orbit”, “rotation”, and “revolution”. Common usage is to say that planets “orbit” about the Sun, which, as you say, describes how a planet travels relative to the Sun. Also common is to say that planets “rotate” about an axis which runs through the center of the planet. Revolution is less common, though is a reasonable synonym for rotation.

      Jeff Mangum

      • rafael says:

        Using “revolve” as a synonym for “rotate” is a new one for me. From elementary school onward, these two terms were used consistently to distinguish between what the Earth does around the Sun vs. what the Earth does around its axis, respectively. I found the description confusing for the same reasons as Jackson.

  8. Ted Ferneza says:

    love that this discussion has been going on for an entire orbit and a half !
    As perceived from Earth of course
    Glocester RI

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