  We present a new, dynamical way to study powers (that is, repetitions) in
Sturmian words based on results from Diophantine approximation theory. As a
result, we provide an alternative and shorter proof of a result by Damanik and
Lenz characterizing powers in Sturmian words [Powers in Sturmian sequences,
Eur. J. Combin. 24 (2003), 377--390]. Further, as a consequence, we obtain a
previously known formula for the fractional index of a Sturmian word based on
the continued fraction expansion of its slope.
