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The Abell 2261 galaxy cluster, with A2261-BCG the bright elliptical galaxy near to the top center.
|Observation data (J2000 epoch)|
|Right ascension||17h 22m 27.173s|
|Declination||+32° 07′ 57.18″|
|Apparent magnitude (V)||~12|
|Number of stars||10 trillion (1013)|
|Apparent size (V)||0.413'× 0.405'|
|2MASX J17222717+3207571, SDSS J172227.18+320757.2, PGC 1981854|
A2261-BCG (short for Abell 2261 Brightest Cluster Galaxy) is a huge elliptical galaxy in the cluster Abell 2261. One of the largest galaxies known, A2261-BCG is estimated to have a diameter of a million light-years, some 10 times larger than the Milky Way. It is the brightest and the most massive galaxy in the cluster, and has the largest galactic core ever observed, spanning more than 10,000 light-years.
The cD elliptical galaxy, located at least 3 billion light-years from Earth, is also well known as a radio source. Its core is highly populated by a dense number of old stars, but is mysteriously diffuse, giving it a large core. On September 10, 2012, using Hubble Space Telescope's Wide Field Camera 3, scientists found out that there was no supermassive black hole present in the center. This may be the likely cause of its diffuse and large core, but it contradicts modern galactic evolutionary theories. A huge cD galaxy like A2261-BCG would be expected to have a supermassive black hole concentrated at its center.
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