195 results about "Effective radius" patented technology

The effective radius or half-light radius (Rₑ) of a galaxy is the radius at which half of the total light of the system is emitted. This assumes the galaxy has either intrinsic spherical symmetry or is at least circularly symmetric as viewed in the plane of the sky. Alternatively, a half-light contour, or isophote, may be used for spherically and circularly asymmetric objects. Rₑ is an important length scale in de Vaucouleurs ∜(R) law, which characterizes a specific rate at which surface brightness decreases as a function of radius: I(R)=Iₑ·e⁻⁷·⁶⁷⁽∜⁽ᴿ/ᴿₑ⁾⁻¹⁾ where Iₑ is the surface brightness at R=Rₑ.