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> Galaxy Centaurus A

Galaxy Centaurus A

author: Noao/Nasa/Stsci/Novapix

reference: a-gax51-28001

Image Size 300 DPI: 24 * 16 cm

NGC 5128 is the nearest large elliptical galaxies to our sun. It is also the nearest of the giant radio galaxies, possessing an active galactic nucleus (AGN) and optically one of the most luminous galaxies in the sky. Among many other things NGC 5128 is also the prototypical postmerger elliptical galaxy. Structural peculiarities including the prominent rotating disk of stars and gas and the complex shell structure of its halo point to a large scale merger within the last billion years. Tidal streams of young stars have also been identified in the halo of NGC 5128 thought to have occurred by cannibalization of a nearby gas rich dwarf galaxy some 300 million years ago, long after the large scale merger. Elliptical galaxies are typically devoid of gas, dust and young stars. The unexpected presence of gas rich disk elements within the structure of NGC 5128 supports the current belief that accretions and mergers of low mass galaxies may be an important agent in the evolution of galaxy formation. As a radio galaxy, NGC 5128 belongs to the subgroup of galaxies called Active Galaxies, which include Quasars, Seyfert galaxies, Blazars and and Radio Galaxies. Active galaxies are distinguished by their prodigious energy output which cannot be explained by their stellar populations and must have another source. Active galaxies have in common an "Active Galactic Nucleus (AGN)" which is believed responsible for their prodigious energy output. Supermassive black holes are almost certainly the central engines of Active Galactic Nuclei, powering the enormous outflows of energy which characterize this subgroup of bright galaxies.

Keywords for this photo:

1998 - ACTIVE GALAXY - ACTIVE GALAXY NUCLEUS - AGN - ASTRONOMY - BLACK HOLE - CENTAURUS - CENTAURUS A - ELLIPTICAL GALAXY - GALACTIC BLACK HOLE - GALAXY - HST - HUBBLE SPACE TELESCOPE - NGC 5128 - RADIOGALAXY - SOUTHERN HEMISPHERE - STAR - STAR FORMATION - SUPERMASSIVE BLACK HOLE - WIDE FIELD PLANETARY CAMERA -