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The age problem in the ΛCDM model is re‐examined. We define the elapsed time  T  of an object as its age plus the age of the Universe when it was born. Therefore in any cosmology  T  must be smaller than the age of the Universe. For the old quasar APM  08279+ 5255 at   z = 3.91 , previous studies have determined that the best‐fitting value of  T , 1σ lower limit and lowest limit to  T  are 2.3, 2.0 and 1.7 Gyr, respectively. Constrained from SNIa + R + A + d  , SNIa + R + A + d + H ( z )  and  WMAP 5+2dF+SNLS+ HST +BBN, the ΛCDM model can only accommodate   T ( z = 3.91) = 1.7  Gyr at 1σ deviation. Constrained from  WMAP 5 results only, the ΛCDM model can only accommodate   T ( z = 3.91) = 1.7  Gyr at 2σ deviation. In all these cases, we found that the ΛCDM model accommodates the total age (14 Gyr for   z = 0 ) of the Universe estimated from old globular clusters, but cannot accommodate statistically the 1σ lower limit to the best‐fitting age of APM  08279+ 5255 at   z = 3.91 . These results imply that the ΛCDM model may suffer from an age problem.

The age problem in the Λ CDM model