## Quick Reference

A distance defined as the ratio of the velocity of light, *c*, to the value of the Hubble constant, *H*_{0}. 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.

**From:**
Hubble radius
in
A Dictionary of Astronomy »

*Subjects:*
Astronomy and Astrophysics.