Are Galaxy Clusters Suggesting an Accelerating Universe?
  The present cosmic accelerating stage is discussed through a new kinematic
method based on the Sunyaev- Zel'dovich effect (SZE) and X-ray surface
brightness data from galaxy clusters. By using the SZE/X-ray data from 38
galaxy clusters in the redshift range $0.14 \leq z \leq 0.89 $ [Bonamente et
al., Astrop. J. {\bf 647}, 25 (2006)] it is found that the present Universe is
accelerating and that the transition from an earlier decelerating to a late
time accelerating regime is relatively recent. The ability of the ongoing
Planck satellite mission to obtain tighter constraints on the expansion history
through SZE/X-ray angular diameters is also discussed. Our results are fully
independent on the validity of any metric gravity theory, the possible matter-
energy contents filling the Universe, as well as on the SNe Ia Hubble diagram
from which the presenting accelerating stage was inferred.
