Astrophysics (Index)About

effective radius

(Re, half-light radius)
(radius of a galaxy within which 1/2 the light is emitted)

Effective radius (aka half-light radius) is a measure of the size of a galaxy that accommodates the fact that while galaxies grow thinner (fewer stars, less gas) with distance from the center, they don't have well-defined edges. The effective radius is defined to be the radius within which 1/2 the galaxy's light is emitted.

Further reading:

Referenced by pages:
fundamental plane
Kormendy Relation