Figure: A redshift versus magnitude plot reveals a linear relationship between recession velocity and distance.
A linear relationship between the distance to a galaxy (R) and the velocity with which that galaxy is receeding from us (v) due to the overall expansion of the universe. The relation is
v = Ho R
where Ho is the constant of proportionality known as Hubble's constant. The present "best" value of the Hubble constant is about 70 kilometers per second per Megaparsec.
Figure: A redshift versus magnitude plot reveals a linear
relationship between recession velocity and distance.