How old is the Universe ? Setting new constraints on the age of the Universe

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 H0 = 70± 15 km s −1 Mpc, we find the age of the universe to be 13.2 −2.0 Gyr (1σ), 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± 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 −1.0 Gyr. Without the assumption of any priors, universes older than 18 Gyr are ruled out by the data at the 90% confidence level.