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We place tight constraints on the redshift-averaged, effective value of theequation of state of dark energy, w, using only the absolute ages of Galacticstars and the observed position of the first peak in the angular power spectrumof the CMB. We find w<-0.8 at the 68% confidence level. If we further considerthat w > -1, this finding suggests that within our uncertainties, dark energyis indistinguishable from a classical vacuum energy term.  We detect a correlation between the ages of the oldest galaxies and theirredshift. This opens up the possibility of measuring w(z) by computing therelative ages of the oldest galaxies in the universe as a function of redshift,dz/dt. We show that this is a realistic possibility by computing dz/dt at z~0from SDSS galaxies and obtain an independent estimate for the Hubble constant,H_0 = 69 \pm 12 km s-1 Mpc-1. The small number of galaxies considered at z>0.2does not yield, currently, a precise determination of w(z), but shows that theage--redshift relation is consistent with a Standard LCDM universe with $w=-1$.Comment: Submitted to Ap

Constraints on the Equation of State of Dark Energy and the Hubble Constant from Stellar Ages and the Cosmic Microwave Background