The galaxy is classified as a supergiant elliptical (E) to lenticular (S0) and is the brightest galaxy in A2029 (hence its other designation A2029-BCG; BCG meaning brightest cluster galaxy). The galaxy’s morphological type is debated due to it possibly being shaped like a flat disc but only visible from Earth at its broadest dimensions. However, most lenticulars have sizes ranging from 15 to 37 kpc (50 to 120 thousand ly).[specify]
IC 1101 is among the largest known galaxies, but there is debate in the astronomical literature about how to define the size of such a galaxy. Photographic plates of blue light from the galaxy (sampling stars excluding the diffuse halo) yield an effective radius (the radius within which half the light is emitted) of 65 ± 12 kpc (212 ± 39 thousand ly). The galaxy has a very large halo of much lower intensity “diffuse light” extending to a radius of 600 kpc (2 million ly). The authors of the study identifying the halo conclude that IC 1101 is “possibly one of the largest and most luminous galaxies in the universe”.
Like most large galaxies, IC 1101 is populated by a number of metal-rich stars, some of which are seven billion years older than the Sun, making it appear golden yellow in color. It has a bright radio source at the center, which is likely associated with an ultramassive black hole in the mass range of 40–100 billion M☉, one of the largest known black holes in the universe.