List of galaxies by surface brightness


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. Where is surface brightness, is total magnitude, and is the total area in square arcseconds. Area is calculated using the formula for an ellipse;, where is the semi-major axis and 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:, which simplifies to.
GalaxyImageSurface BrightnessApparent MagnitudeDimensionsDistanceTypeNotesCitations
Messier 8220.918.49x4 arcminutes12SpiralHas rapid star formation due to interactions with M81 making red streaks.
Messier 3220.938.18x6 arcminutes2.5EllipticalSatellite galaxy of the Andromeda Galaxy
NGC 363221.1710.63x2 arcminutes70Spiral
Messier 8121.336.921x10 arcminutes11.6SpiralFaintest galaxy visible to the naked eye, despite the naked eye limiting magnitude of a star being fainter, surface brightness limits this for galaxies.
Whirlpool Galaxy21.748.411x7 arcminutes31SpiralHas a nearby galaxy in a merger.
Messier 5821.919.85.5x4.5 arcminutes62Spiral
Andromeda Galaxy22.193.44178x63 arcminutes2.54Spiral/ringIts core is significantly brighter than it's outer disk.
Messier 8722.459.67 arcminutes54EllipticalRoughly round, so is used along with angular diameter.
Messier 4922.69.49x7.5 arcminutes60Elliptical
Triangulum Galaxy235.770.8x41.7 arcminutes3Spiral