# Gyrochronology, the formula is empirical ?

The formula used in Gyrochronology that relates a star's Period of Rotation-Mass-Age is empirical?

This news How to Learn a Star’s True Age

"“A star’s rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age,"

pointed to this paper THE KEPLER CLUSTER STUDY: STELLAR ROTATION IN NGC6811
and later I found this one (gyro_background) with original work.

But I couldnt find a justification for the formula. Is the Period proportional to $age^{{1/2}}$ only an empirical result?

It seems to me that the formula is a data fit and not a direct result of a calculation of the stellar intrinsic dynamics. The rate of mass loss by radiation must have a 'word to say' in the formula.
Any help is welcome.

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Please define your terms. What is $t$ here? Period of what? Yes, in principle we could read the papers, but you are asking for some help so it would behoove you to do a bit of work to make our lives easier. –  dmckee May 25 '11 at 2:17
I will, until now I had'nt time enough to elaborate. –  Helder Velez May 25 '11 at 8:40