This is a list of galaxies sorted by surface brightness. Surface brightness is a measure of how bright a diffuse object like a galaxy or nebula appears over its extended surface. The brightness over the entire galaxy is called apparent magnitude.
Table The surface brightness is calculated via S = m + 2.5 log 10 A {\displaystyle S=m+2.5\log _{10}A} . Where S {\displaystyle S} is surface brightness, m {\displaystyle m} is total magnitude, and A {\displaystyle A} is the total area in square arcseconds. Area is calculated using the formula for an ellipse; π a b {\displaystyle \pi ab} , where a {\displaystyle a} is the semi-major axis and b {\displaystyle b} is the semi-minor axis. Each axis is half of the dimension, because each dimension is the entire length/height but the axis is only the length/height to the centre, this combined with the symmetry of an ellipse means that half the dimension is the axis. Combining this with the original formula we get: S = m + 2.5 log 10 ( π a 2 b 2 ) {\displaystyle S=m+2.5\log _{10}(\pi {\frac {a}{2}}{\frac {b}{2}})} , which simplifies to S = m + 2.5 log 10 π a b 4 {\displaystyle S=m+2.5\log _{10}{\frac {\pi ab}{4}}} .
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