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Recent improvements in astronomical observations lead to the conclusion that the Hubble constant lies between 60 and 80 Mpc km$^{-1}$ sec$^{-1}$ and the age of the universe between 11 and 14 Gigayears. Taken together with recent…

General Relativity and Quantum Cosmology · Physics 2007-05-23 H. Pierre Noyes

Although cosmologists have been trying to determine the value of the Hubble constant for nearly 65 years, they have only succeeded in limiting the range of possibilities: most of the current observational determinations place the Hubble…

Astrophysics · Physics 2009-10-22 J. G. Bartlett , A. Blanchard , J. Silk , M. S. Turner

The Hubble constant, which measures the expansion rate, together with the total energy density of the Universe, sets the size of the observable Universe, its age, and its radius of curvature. Excellent progress has been made recently toward…

Astrophysics · Physics 2008-11-26 Wendy L. Freedman

We present a method to compute the probability distribution function of the (true) Hubble constant and the age of the universe, given the estimate of the Hubble constant in our nearby galaxy samples. Our method takes into account both the…

Astrophysics · Physics 2009-10-28 T. Nakamura , Y. Suto

Considerable progress has been made in determining the Hubble constant over the past two decades. We discuss the cosmological context and importance of an accurate measurement of the Hubble constant, and focus on six high-precision…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Wendy L. Freedman , Barry F. Madore

I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first…

Astrophysics · Physics 2015-05-13 Neal Jackson

While the recent discovery of the Cepheid variables in the Virgo cluster galaxies puts additional support for the Hubble constant $H_0 \sim 80$km/sec/Mpc, a relatively lower value $H_0 \sim 50$km/sec/Mpc is suggested by other distance…

Astrophysics · Physics 2017-02-01 Y. Suto , T. Suginohara , Y. Inagaki

We present a simultaneous analysis of 18 galaxy lenses with time delay measurements. For each lens we derive mass maps using pixelated simultaneous modeling with shared Hubble constant. We estimate the Hubble constant to be 66_{-4}^{+6}…

Cosmology and Nongalactic Astrophysics · Physics 2010-10-05 Danuta Paraficz , Jens Hjorth

We here update the derivation of precise values for the Hubble constant H_0, the age t_0 and the density parameter Omega*h^2 of the universe in the decaying neutrino theory for the ionisation of the interstellar medium (Sciama 1990 a,…

Astrophysics · Physics 2015-06-24 D. W. Sciama

Despite the tremendous advance of observational cosmology, the value of the Hubble constant ($H_0$) is still controversial (the so called ``Hubble tension'') because of the inconsistency between local/late-time measurements and those…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-19 Andrea Cimatti , Michele Moresco

The age of the universe in the Big Bang model can be calculated from three parameters: Hubble's constant, h; the mass density of the universe, Omega_m; and the cosmological constant, Omega_lambda. Recent observations of the cosmic microwave…

Astrophysics · Physics 2009-06-16 Charles H. Lineweaver

Rapid progress has been made recently toward the measurement of cosmological parameters. Still, there are areas remaining where future progress will be relatively slow and difficult, and where further attention is needed. In this review,…

Astrophysics · Physics 2009-10-31 Wendy L. Freedman

By coupling observations of type Ia supernovae with results obtained from the best available numerical models we constrain the Hubble constant, independently of any external calibrators. We find an absolute lower limit of Ho > 50 km/s/Mpc.…

Astrophysics · Physics 2009-11-10 M. Stritzinger , B. Leibundgut

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 via the precision…

Astrophysics · Physics 2009-11-06 I. Ferreras , A. Melchiorri , J. Silk

We use 28 Hubble parameter, $H(z)$, measurements at intermediate redshifts $0.07 \leq z \leq 2.3$ to determine the present-day Hubble constant $H_0$ in four cosmological models. We measure $H_0 = 68.3^{ +2.7}_{ -2.6 }, 68.4^{ +2.9 }_{ -3.3…

Cosmology and Nongalactic Astrophysics · Physics 2017-01-26 Yun Chen , Suresh Kumar , Bharat Ratra

In this review, the status of measurements of the matter density (Omega), the vaccuum energy density or cosmological constant (Lambda), the Hubble constant (H0), and ages of the oldest measured objects (t0) are summarized. Measurements of…

Astrophysics · Physics 2009-10-30 Wendy L. Freedman

The Megamaser Cosmology Project inferred a value for the Hubble constant given by $H_0=73.9 \pm 3.0 $ km/sec/Mpc. This value was obtained using Bayesian inference by marginalizing over six nuisance parameters, corresponding to the…

Instrumentation and Methods for Astrophysics · Physics 2025-06-23 Shubham Barua , Vyaas Ramakrishnan , Shantanu Desai

For 100 years since galaxies were found to be flying apart from each other, astronomers have been trying to determine how fast. The expansion, characterized by the Hubble constant, H0, is confused locally by peculiar velocities caused by…

Cosmology and Nongalactic Astrophysics · Physics 2023-05-23 R. Brent Tully

Using the relation between distance modulus $(m - M)$ and redshift $z$, deduced from Friedman- Robertson-Walker (FRW) metric and assuming different values of deceleration parameter $q_0$. We constrained the Hubble parameter $h$. The…

General Physics · Physics 2016-06-03 C. C. Onuchukwu , A. C. Ezeribe

The cosmological parameters that I will emphasize are the Hubble parameter $H_0 \equiv 100 h$ km s$^{-1}$ Mpc$^{-1}$, the age of the universe $t_0$, the average matter density $\Omega_m$, the baryonic matter density $\Omega_b$, the neutrino…

Astrophysics · Physics 2007-05-23 Joel R. Primack
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