Given the consistency of Hubble constants derived, both locally and at
large recessional velocities, then we can state that
H_{0} falls
within the full-range extremes of 75 ± 1 and 68 ± 5 km/sec/Mpc,
giving formally
Method | Hubble Constant | (Random) | [Systematic] |
Fornax Cluster | 68 km/sec/Mpc | ± 7 (random) | ± 18 [systematic] |
Local Flow | 72 km/sec/Mpc | ± 4 (random) | ± 17 [systematic] |
Tully-Fisher | 76 km/sec/Mpc | ± 2 (random) | ± 8 [systematic] |
Hybrid Methods | 72 km/sec/Mpc | ± 1 (random) | ± 7 [systematic] |
Type Ia SNe | 68 km/sec/Mpc | ± 5 (random) | ± 8 [systematic] |
Modal Average: | 72 km/sec/Mpc | ± 5 (random) | ± 12 [systematic] |
Major Systematics: | ± 11% [FLOWS] | ± 5% [LMC] | ± 4% [Fe/H] |
A value of the Hubble constant, in combination with an independent estimate of the average density of the Universe, can be used to estimate a dynamical age for the Universe (e.g., see Figure 39). For a value of of H_{0} = 72 (± 2)_{r} km/sec/Mpc, the age ranges from a high of ~ 12 Gyr for a low-density ( = 0.2) Universe, to a young age of ~ 9 Gyr for a critical-density ( = 1.0) Universe. These ages change to 15 and 7.5 Gyr, respectively allowing for a systematic error of ± 10 km/sec/Mpc.
Other, independent constraints on the age of the Universe exist; most
notably, the ages of the oldest stars, as typified by Galactic globular
clusters. These ages traditionally are thought to fall in the range
of 14 ± 2 Gyr
(Chaboyer et al. 1996),
however
the subdwarf parallaxes obtained by the Hipparcos satellite
(Reid 1997)
may reduce these ages considerably. For = 14 Gyr and
= 1.0,
H_{0} would have to be ~45 km/sec/Mpc. If
constrained by the stellar ages, and interpreted within the context of
the standard Einstein-de Sitter model, our value of H_{0}
= 72 km/sec/Mpc, is incompatible with a high-density