A distance defined as the ratio of the velocity of light, c, to the value of the Hubble constant, H0. This gives the distance from the observer at which the recession velocity of a galaxy would equal the speed of light. Roughly speaking, the Hubble radius is the radius of the observable Universe. Current observations place the Hubble constant at around 71 km/s/Mpc, which gives a Hubble radius of 13.7 billion l.y.
Subjects: Astronomy and Astrophysics.