Effective radius

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The effective radius R e includes half of all light emitted by an object.

The effective radius , the effective radius or half-light radius describes the radius or , in the half of the luminance of an astronomical object is emitted:

The effective radius is used to describe star clusters and galaxies , especially to calculate the course of the surface brightness of a bulge or an elliptical galaxy with the help of the De Vaucouleurs formula .

This measured variable depends on the observation instrument used, because with smaller instruments the outer areas of the astronomical object can be below the limit brightness .

See also


  • Peter Schneider: Introduction to Extragalactic Astronomy and Cosmology . Springer Verlag, Berlin 2005, ISBN 3-540-25832-9 .