Hubble's constant

noun Astronomy.
  1. the ratio of the recessional velocity of galaxies to their distance from the sun, with current measurements of its value ranging from 50 to 100 km/sec per megaparsec.

Origin of Hubble's constant

First recorded in 1950–55; after E. P. Hubble
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018