Why does the Sun have different day lengths, but not the gas giants?












3












$begingroup$


The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force works, the equator must move faster than the poles.



Question: if this works, why do Jupiter/Saturn/Uranus/Neptune have well-defined days? Why don't the equators of these planets rotate faster than the poles as well? For example, Wikipedia's article on Jupiter gives the length of a Jovian day as 9h 55m 30s, which is so precise that it implies Jupiter does not have a rotational period which varies with latitude.










share|improve this question









$endgroup$

















    3












    $begingroup$


    The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force works, the equator must move faster than the poles.



    Question: if this works, why do Jupiter/Saturn/Uranus/Neptune have well-defined days? Why don't the equators of these planets rotate faster than the poles as well? For example, Wikipedia's article on Jupiter gives the length of a Jovian day as 9h 55m 30s, which is so precise that it implies Jupiter does not have a rotational period which varies with latitude.










    share|improve this question









    $endgroup$















      3












      3








      3





      $begingroup$


      The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force works, the equator must move faster than the poles.



      Question: if this works, why do Jupiter/Saturn/Uranus/Neptune have well-defined days? Why don't the equators of these planets rotate faster than the poles as well? For example, Wikipedia's article on Jupiter gives the length of a Jovian day as 9h 55m 30s, which is so precise that it implies Jupiter does not have a rotational period which varies with latitude.










      share|improve this question









      $endgroup$




      The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force works, the equator must move faster than the poles.



      Question: if this works, why do Jupiter/Saturn/Uranus/Neptune have well-defined days? Why don't the equators of these planets rotate faster than the poles as well? For example, Wikipedia's article on Jupiter gives the length of a Jovian day as 9h 55m 30s, which is so precise that it implies Jupiter does not have a rotational period which varies with latitude.







      the-sun rotation gas-giants






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 1 hour ago









      AllureAllure

      40519




      40519






















          1 Answer
          1






          active

          oldest

          votes


















          4












          $begingroup$

          It's a matter of how "day" is defined.



          Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:




          The equations for W for Jupiter, Saturn, Uranus and Neptune refer to the rotation of their magnetic fields (System III)




          The assumption is that whatever's generating the magnetic field forms a reasonably coherent mass that's rotating at a uniform speed. This produces a periodic variation in the radio emissions of the planet, which is used to measure the rotation speed of that object.



          We're reasonably certain the Sun doesn't have a coherent core, so measuring the rotation speed of the magnetic field doesn't provide a useful definition of the Sun's rotation speed.






          share|improve this answer









          $endgroup$













            Your Answer





            StackExchange.ifUsing("editor", function () {
            return StackExchange.using("mathjaxEditing", function () {
            StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
            StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
            });
            });
            }, "mathjax-editing");

            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "514"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            autoActivateHeartbeat: false,
            convertImagesToLinks: false,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: null,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            noCode: true, onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














            draft saved

            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fastronomy.stackexchange.com%2fquestions%2f30087%2fwhy-does-the-sun-have-different-day-lengths-but-not-the-gas-giants%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            4












            $begingroup$

            It's a matter of how "day" is defined.



            Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:




            The equations for W for Jupiter, Saturn, Uranus and Neptune refer to the rotation of their magnetic fields (System III)




            The assumption is that whatever's generating the magnetic field forms a reasonably coherent mass that's rotating at a uniform speed. This produces a periodic variation in the radio emissions of the planet, which is used to measure the rotation speed of that object.



            We're reasonably certain the Sun doesn't have a coherent core, so measuring the rotation speed of the magnetic field doesn't provide a useful definition of the Sun's rotation speed.






            share|improve this answer









            $endgroup$


















              4












              $begingroup$

              It's a matter of how "day" is defined.



              Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:




              The equations for W for Jupiter, Saturn, Uranus and Neptune refer to the rotation of their magnetic fields (System III)




              The assumption is that whatever's generating the magnetic field forms a reasonably coherent mass that's rotating at a uniform speed. This produces a periodic variation in the radio emissions of the planet, which is used to measure the rotation speed of that object.



              We're reasonably certain the Sun doesn't have a coherent core, so measuring the rotation speed of the magnetic field doesn't provide a useful definition of the Sun's rotation speed.






              share|improve this answer









              $endgroup$
















                4












                4








                4





                $begingroup$

                It's a matter of how "day" is defined.



                Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:




                The equations for W for Jupiter, Saturn, Uranus and Neptune refer to the rotation of their magnetic fields (System III)




                The assumption is that whatever's generating the magnetic field forms a reasonably coherent mass that's rotating at a uniform speed. This produces a periodic variation in the radio emissions of the planet, which is used to measure the rotation speed of that object.



                We're reasonably certain the Sun doesn't have a coherent core, so measuring the rotation speed of the magnetic field doesn't provide a useful definition of the Sun's rotation speed.






                share|improve this answer









                $endgroup$



                It's a matter of how "day" is defined.



                Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:




                The equations for W for Jupiter, Saturn, Uranus and Neptune refer to the rotation of their magnetic fields (System III)




                The assumption is that whatever's generating the magnetic field forms a reasonably coherent mass that's rotating at a uniform speed. This produces a periodic variation in the radio emissions of the planet, which is used to measure the rotation speed of that object.



                We're reasonably certain the Sun doesn't have a coherent core, so measuring the rotation speed of the magnetic field doesn't provide a useful definition of the Sun's rotation speed.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 1 hour ago









                MarkMark

                1,599619




                1,599619






























                    draft saved

                    draft discarded




















































                    Thanks for contributing an answer to Astronomy Stack Exchange!


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    Use MathJax to format equations. MathJax reference.


                    To learn more, see our tips on writing great answers.




                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fastronomy.stackexchange.com%2fquestions%2f30087%2fwhy-does-the-sun-have-different-day-lengths-but-not-the-gas-giants%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    Popular posts from this blog

                    Knooppunt Holsloot

                    Altaar (religie)

                    Gregoriusmis