Meibom, Søren; Barnes, Sydney A.; Platais, Imants; Gilliland, Ronald L.; Latham, David W.; Mathieu, Robert D. (5 January 2015). "A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster". Nature. doi:http://dx.doi.org/10.1038%2Fnature14118 [Broken]. The rotational velocity of a G-type or smaller star apparently indicates the age of the star. Good tool, assuming this observation holds generally. For example, if you wanted to find a star system like ours, then look for G-type stars with a period of rotation similar to the sun: 26 days. Since this not my area, can someone point out where the lost angular momentum goes over time. The early Earth's day length was considerably shorter than it is today. The Earth-moon system has transferred angular momentum to the moon over time. Correct? So stars in the study slowed rotation is a similar way? Does this imply planets?