Site MapHelpFeedback

barred spiral galaxy  A spiral galaxy in which the nucleus is crossed by a bar. The spiral arms start at the ends of the bar.
elliptical galaxy  A galaxy having an ellipsoidal shape and lacking spiral arms.
galactic cannibalism  The capture and disruption of one galaxy by another.
Hubble’s constant (H)  The rate at which the recession speeds of galaxies increase with distance. Current estimates of Hubble’s constant range from 50 to 100 kilometers per second per megaparsec.
Hubble’s law  The linear relationship between the recession speeds of galaxies and their distances. The slope of Hubble’s law is Hubble’s constant.
irregular galaxy  A galaxy having an amorphous shape and lacking symmetry.
normal spiral galaxy  A galaxy in which the spiral arms emerge from the nucleus.
primary distance indicator  A type of object, such as a Cepheid variable, for which we know the size or brightness by observing them in the Milky Way.
secondary distance indicator  A type of object for which we know the size or brightness because objects of that type have been found in nearby galaxies.
spiral galaxy  A flattened galaxy in which hot stars, interstellar clouds, and other young objects form a spiral pattern.

AstronomyOnline Learning Center

Home > Chapter 23 > Glossary