IC 1101

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IC 1101
Abell 2029.png
A2029 as seen from the Chandra X-ray Observatory (left) and European Southern Observatory (right)
Observation data (J2000 epoch)
Constellation Virgo
Right ascension 15h 10m 56.1s[1]
Declination +05° 44′ 41″[1]
Redshift 23370 ± 30 km/s[1]
Distance 1.07 Gly
Type E3[1]
Number of stars 100 trillion (1014)
Apparent dimensions (V) 1'.2 × 0'.6[1]
Apparent magnitude (V) 14.7[1]
Other designations
UGC 9752,[1] PGC 54167[1]
See also: Galaxy, List of galaxies

IC 1101 is a supergiant elliptical galaxy at the center of the Abell 2029 galaxy cluster, approximately 1.07 billion light years (309 megaparsecs) from Earth.


The galaxy is classified as a supergiant elliptical (E) to lenticular (S0)[2] and is the brightest galaxy in A2029 (hence its other designation A2029-BCG; BCG meaning Brightest cluster galaxy).[3][4] The galaxy's morphological type is debated due to its possibility being shaped like a flat disc, but only seen from Earth at a different angle. However, most lenticulars have sizes ranging from 50,000 to 120,000 light-years. If IC 1101 is a lenticular galaxy, it would be the largest ever detected.

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 a black hole, however it is unlikely that it holds the largest black hole in the universe. It is most likely that the central black hole of IC 1101 has a mass no greater than 5 billion solar masses, which is four times smaller than some of the largest black holes known.


The galaxy was discovered on June 19, 1790 by the British astronomer Frederick William Herschel I. It was catalogued in 1895, or more than 100 years later, by John Louis Emil Dreyer as the 1,101st object of the Index Catalogue of Nebulae and Star Clusters (IC). 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.

Wrong information?[edit]

There have been some wrong information about IC 1101 proposed in the past. Some of which are the ones below:


In the third episode of Season 1 of How the Universe Works by the Discovery Channel, named "Alien Galaxies", they made a mistake of the galaxy's catalogue number, turning it to "IC 1011" instead of IC 1101. It took a few months before the mistake has been corrected. IC 1011 is a compact elliptical galaxy with the size comparable only to dwarf galaxies. The staff of How the Universe Works said that it was some form of typographical error. Even so, the episode is still being viewed.


Map of the constellation Virgo showing the approximate location of IC 1101
Cercle rouge 100%.svg
Map of the constellation Virgo showing
the location of IC 1101 (within the red circle)

Data on the Internet claiming the galaxy being in the constellation Serpens. However, it was turned out to be incorrect. Its coordinates in J2000 are 15h 10m 56.1s in right ascension and +05° 44' 41" on declination; placing the galaxy within the vicinity of the constellation Virgo. It is still unknown where the claim came from, and how the claim spread so quickly.


Probably the greatest mistake about IC 1101 was its size. In 1989, news reports claimed IC 1101's diameter is 5 to 6 million light years, making it the largest galaxy known in the observable universe, which is incorrect. The size reported was actually the size of the A2029 X-ray emission, seen as the pinkish glow on the picture above, which is not IC 1101. The galaxy is actually the central yellow glow on the optical image. With the revised figure, 1.407 arcminutes at a distance of 1.071 billion light-years, the galaxy's diffuse stellar halo light was found to only have a diameter of 2.8 million light-years. This fact appears to have been unreported for the next 24 years. But even with the revised size, it is still the largest known galaxy in terms of breadth.[5] For comparison, NGC 262, the next largest galaxy, has an H I halo with a diameter of 2.6 million light-years (H I halos are considered to be stellar halos, as these are regions of neutral hydrogen, a main component of stars) It is more than 28 times the size of the Milky Way in diameter, and more than 400 times its volume. It may be as much as a thousand times more massive, or about the same mass as the Virgo Cluster. IC 1101 reached its size due to multiple collisions of galaxies over billions of years.

See also[edit]


  1. ^ a b c d e f g h "NASA/IPAC Extragalactic Database". Results for IC 1101. Retrieved 2006-11-11. 
  2. ^ "Data for IC 1101". SIMBAD Astronomical Database. 
  3. ^ http://arxiv.org/PS_cache/astro-ph/pdf/0209/0209205v2.pdf
  4. ^ Uson, Juan M.; Boughn, Stephen P.; Kuhn, Jeffrey R. (October 1990). "The central galaxy in Abell 2029 - an old supergiant". Science 250 (4980): 539–540. Bibcode:1990Sci...250..539U. doi:10.1126/science.250.4980.539. 
  5. ^ Clarke, Blanton, & Sarazin, Complex Cooling Core of A2029

External links[edit]

Coordinates: Sky map 15h 10m 56.1s, +05° 44′ 41″