gigaparsecs A distance of one million parsecs (approximately 3,260,000 light-years) is commonly denoted by the megaparsec (Mpc). Astronomers typically measure the distances between neighbouring galaxies and galaxy clusters in megaparsecs. Galactic distances are sometimes given in units of Mpc/h (as in "50/h Mpc"). h is a parameter in the range [0.5,0.75] reflecting the