An Etymological Dictionary of Astronomy and Astrophysics

An indicator of extragalactic distances that relies on → primary calibrators in our Galaxy.
Secondary calibrators of the distance scale depend on statistical measures of the properties of a class of objects, such as the brightness of H II regions, globular clusters, red and blue stars, or the neutral hydrogen 21-cm line width or velocity dispersion (of spiral galaxies), etc. Same as secondary distance indicator.

See also: → secondary; → calibrator.