The Universe is expanding with a Hubble parameter of
H0≈70km/s/Mpc.
These are the units most typically used to state this quantity by astronomers.
To figure out how fast the apparent recession velocity of an object is due to the expansion of the universe, use "Hubble's law":
v=Hd,
whered is just the distance to that object.
Note that this "law" only works for objects which are far enough away that expansion is important compared to proper motion (say, outside of the local group, a fewMpc ) but close enough that 1) the linear approximation to Hubble's law is valid and 2) it doesn't matter which distance measure you used (they all agree in the small distance limit).
As an example, consider the Coma cluster, which is roughly100Mpc away. The apparent recession velocity due to expansion will be
v≈70km/s/Mpc∗100Mpc≈7000km/s.
[1]1Mpc≈3∗1022m
These are the units most typically used to state this quantity by astronomers.
To figure out how fast the apparent recession velocity of an object is due to the expansion of the universe, use "Hubble's law":
where
Note that this "law" only works for objects which are far enough away that expansion is important compared to proper motion (say, outside of the local group, a few
As an example, consider the Coma cluster, which is roughly
[1]
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