So we know that stars slow down as they age. But total angular momentum must be conserved. Where does that angular momentum go?
The dissipation of Earth's tides somehow transfers Earth's angular momentum to the moon (as shown in my answer at http://www.quora.com/Has-the-Earths-rotational-period-always-been-24-hours-If-not-what-was-it-before-and-what-caused-the-change). But where does a star's dissipation go?