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.

The surface brightness is calculated via ${\displaystyle S=m+2.5\log _{10}A}$. Where ${\displaystyle S}$ is surface brightness, ${\displaystyle m}$ is total magnitude, and ${\displaystyle A}$ is the total area in square arcseconds. Area is calculated using the formula for an ellipse; ${\displaystyle \pi ab}$, where ${\displaystyle a}$ is the semi-major axis and ${\displaystyle b}$ 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: ${\displaystyle S=m+2.5\log _{10}(\pi {\frac {a}{2}}{\frac {b}{2}})}$, which simplifies to ${\displaystyle S=m+2.5\log _{10}{\frac {\pi ab}{4}}}$.

Galaxy	Image	Surface Brightness(mag/arcsecond2)	Apparent Magnitude	Dimensions	Distance(Mly)	Type	Notes	Citations
Messier 82		17.40(Rc) 19.10(r) 20.87(B)	8.4	9x4 arcminutes(540x240 arcseconds)	12	Spiral	Has rapid star formation due to interactions with M81 making red streaks.	[1][2][3]
Messier 32		20.93	8.1	8x6 arcminutes(480x360 arcseconds)	2.5	Elliptical	Satellite galaxy of the Andromeda Galaxy	[4][5]
NGC 3632		21.17	10.6	3x2 arcminutes(180x120 arcseconds)	70	Spiral		[6][7]
Messier 81		21.29(B) 19.30(r)	6.9	21x10 arcminutes(1260x600 arcseconds)	11.6	Spiral	Faintest galaxy visible to the naked eye, despite the naked eye limiting magnitude of a star being fainter, surface brightness limits this for galaxies.[8]	[9][10][11]
Whirlpool Galaxy		21.74	8.4	11x7 arcminutes(660x420 arcseconds)	31	Spiral	Has a nearby galaxy in a merger.[12]	[13][14]
Messier 58		21.91	9.8	5.5x4.5 arcminutes(330x270 arcseconds)	62	Spiral		[15][16]
Andromeda Galaxy		22.19	3.44	178x63 arcminutes(10680x3780 arcseconds)	2.54	Spiral/ring	Its core is significantly brighter than it's outer disk.[17]	[18][19][20]
Messier 87		22.45	9.6	7 arcminutes(138544.23 square arcseconds)	54	Elliptical	Roughly round, so ${\displaystyle \pi r^{2}}$ is used along with angular diameter.	[21][22]
Messier 49		22.6	9.4	9x7.5 arcminutes(540x450 arcseconds)	60	Elliptical		[23][24]
Triangulum Galaxy		23	5.7	70.8x41.7 arcminutes(4248x2502 arcseconds)	3	Spiral		[25][26]