Freeman's law qânun-e Freeman Fr.: loi de Freeman A statistical finding about "normal" → spiral galaxies, whereby there is an upper limit on the mean central → surface brightness of disks. This value is constant for different spiral types, amounting to 21.65 ± 0.30 mag arcsec2 in the B band. Named after K. C. Freeman (1970, Ap.J. 160, 811); → law. |