# Where does a star's angular momentum go as its spin slows down?

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?

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I believe it is carried away through magnetically driven stellar wind. See Lau et al. 2001, Tout & Pringle 1992, Ud-Doula et al. 2009. –  EHN Jul 24 '11 at 17:58

For single stars (doubles also exhibit the spin-to-orbital angular momentum transfer), Rotation braking states:

Stars slowly lose mass by the emission of a stellar wind from the photosphere. The star's magnetic field exerts a torque on the ejected matter, resulting in a steady transfer of angular momentum away from the star.

A first order approximation is that the rotation velocity decreases by the inverse squareroot of time elapsed.

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