There are three independent techniques for determining the age of the universe : via cosmochronology of long-lived radioactive nuclei , via stellar modelling and population synthesis of the oldest stellar populations , and , most recently , via the precision cosmology that has become feasible with the mapping of the acoustic peaks in the cosmic microwave background .
We demonstrate that all three methods give completely consistent results , and enable us to set rigorous bounds on the maximum and minimum ages that are allowed for the universe .
We present new constraints on the age of the universe by performing a multiband colour analysis of bright cluster ellipticals over a large redshift range ( 0.3 < z < 0.9 ) , which allows us to infer the ages of their stellar populations over a wide range of possible formation redshifts and metallicities .
Applying a conservative prior to Hubble ’ s constant of H _ { 0 } = 70 \pm 15 km s ^ { -1 } Mpc ^ { -1 } , we find the age of the universe to be 13.2 ^ { +3.6 } _ { -2.0 } Gyr ( 1 \sigma ) , in agreement both with the estimates from type Ia supernovae , as well as with the latest uranium decay estimates , which yield an age for the Milky Way of 12.5 \pm 3 Gyr .
If we combine the results from cluster ellipticals with the analysis of the angular power spectrum of the cosmic microwave background and with the observations of type Ia supernovae at high redshift , we find a similar age : 13.4 ^ { +1.4 } _ { -1.0 } Gyr .
Without the assumption of any priors , universes older than 18 Gyr are ruled out by the data at the 90 % confidence level .