IC 1101
Last updated: 01/07/2019 | U.S.A: 07/01/2019
IC 1101 is an elliptical galaxy at the center of the Abell 2029 galaxy cluster and it is a supergiant. It is the brightest in the Abell as of 2019, it is the largest galaxy discovered so far and is located about 1 billion light-years from Earth.
British astronomer, Fredrick William Herschel I, discovered the galaxy on 19 June 1790. At its discovery, it was identified as a nebulous feature. Following Edwin Hubble's 1932 discovery that some of the "nebulous features" were actually independent galaxies, subsequent analysis of objects in the sky were conducted and IC 1101 was therefore found to be one of the independent galaxies.
The galaxy is classified as a supergiant elliptical to lenticular 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).
IC 1101 is among the largest known galaxies, but there is a 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 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.
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