Hubble constant concept from the Astronomy knowledge base

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Hubble constant
(H₀)

subject fact

Hubble constant has symbol H₀ has source: Lightman, A., Brawer, R. 1990 The Lives and Worlds of Modern Cosmologists, Harvard University Press, 2001-09-27 09:32:59.0
has value 75 km/s/Mpc has source: Clark, S. 1997 Towards the Edge of the Universe, Wiley, 2001-09-27 09:32:59.0
has rate of change non-zero because gravity is slowing down the rate of expansion of the universe has source: Lightman, A., Brawer, R. 1990 The Lives and Worlds of Modern Cosmologists, Harvard University Press, 2001-09-27 09:32:59.0
has unit km/s/Mpc has source: Clark, S. 1997 Towards the Edge of the Universe, Wiley, 2001-09-27 09:32:59.0
has definition Hubble's constant in units of 100 km s^-1 Mpc^-1. has source: Hopkins, J. 1976 Glossary of Astronomy and Astrophysics, University of Chicago Press, 2001-09-27 09:32:58.0
has definition The present expansion rate of the universe, in units of kilometers per second per megaparsec. The larger the Hubble constant, the younger the universe. has source: Croswell, K. 1995 The Alchemy of the Heavens, Anchor Books, 2001-09-27 09:32:58.0
has definition According to Hubble's law, discovered by Edwin Hubble in 1929, distant galaxies are receding from us, on average, with a speed equal to the product of the Hubble constant and the distance to the galaxy. Hubble's "constant" is independent of distance, but actually decreases slowly in time as the expansion is slowed by the gravitational pull of each galaxy on all the others. The present value is somewhere between 15 and 30 kilometers per second per million light-years. has source: Guth, A.H. 1997 The Inflationary Universe, Addison-Wesley, 2001-09-27 09:32:58.0
has definition The constant of proportionality in the Hubble law. Its value must vary with time, so it is often referred to as the Hubble parameter. The Hubble constant is generally used to mean the value of the Hubble parameter at the current epoch, and is somewhere between 50 and 100 km/s/Mpc with possibly a value close to 75 km/s/Mpc. has source: Clark, S. 1997 Towards the Edge of the Universe, Wiley, 2001-09-27 09:32:58.0
has definition The rate at which the universe expands, equal to approximately fifty kilometers of velocity per megaparsec of distance. has source: Ferris, T. 1988 Coming of Age in the Milky Way, Morrow, 2001-09-27 09:32:58.0
has definition The rate of expansion of the universe. The Hubble constant is equal to the recessional speed of a distant galaxy, divided by its distance from us. Assuming a homogeneous and isotropic universe, the recessional speed of a distant galaxy is proportional to its distance; thus the Hubble constant as determined by any receding galaxy should be the same, yielding a universal rate of expansion of the universe. According to estimates, the current value of the Hubble constant is approximately 100 km/s/Mpc, meaning that the distance between any two distant galaxies will double in about 10 billion years at the current rate of expansion. has source: Lightman, A., Brawer, R. 1990 The Lives and Worlds of Modern Cosmologists, Harvard University Press, 2001-09-27 09:32:59.0
is an instance of astronomical constant 2001-09-27 09:32:58.0

Hubble constant	has symbol H₀
	has value 75 km/s/Mpc
	has rate of change non-zero because gravity is slowing down the rate of expansion of the universe
	has unit km/s/Mpc
	has definition Hubble's constant in units of 100 km s^-1 Mpc^-1.
	has definition The present expansion rate of the universe, in units of kilometers per second per megaparsec. The larger the Hubble constant, the younger the universe.
	has definition According to Hubble's law, discovered by Edwin Hubble in 1929, distant galaxies are receding from us, on average, with a speed equal to the product of the Hubble constant and the distance to the galaxy. Hubble's "constant" is independent of distance, but actually decreases slowly in time as the expansion is slowed by the gravitational pull of each galaxy on all the others. The present value is somewhere between 15 and 30 kilometers per second per million light-years.
	has definition The constant of proportionality in the Hubble law. Its value must vary with time, so it is often referred to as the Hubble parameter. The Hubble constant is generally used to mean the value of the Hubble parameter at the current epoch, and is somewhere between 50 and 100 km/s/Mpc with possibly a value close to 75 km/s/Mpc.
	has definition The rate at which the universe expands, equal to approximately fifty kilometers of velocity per megaparsec of distance.
	has definition The rate of expansion of the universe. The Hubble constant is equal to the recessional speed of a distant galaxy, divided by its distance from us. Assuming a homogeneous and isotropic universe, the recessional speed of a distant galaxy is proportional to its distance; thus the Hubble constant as determined by any receding galaxy should be the same, yielding a universal rate of expansion of the universe. According to estimates, the current value of the Hubble constant is approximately 100 km/s/Mpc, meaning that the distance between any two distant galaxies will double in about 10 billion years at the current rate of expansion.
	is an instance of astronomical constant