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NGC 5128 - Centaurus A

Description of object:

Centaurus A is one of the most extraordinary galaxies in the southern starry sky, both in appearance and in its manifold structures. With a distance of "only" 11 million light-years it is very close to the solar system and therefore one of the best explored galaxies outside the local group. Together with Messier 83, Centaurus A forms the center of a nearby group of galaxies outside the local group.

It is the closest radio galaxy to our Milky Way and the third brightest radio source in the sky. Astronomers still disagree about its morphological type, with some researchers classifying it as an elliptical galaxy of type E(p), and others as a lenticular galaxy of type S0. Their characteristic optical feature is the clearly visible, "bent" dust band that traverses the galaxy.

It seems clear that Centaurus A is probably the result of the fusion of a large elliptical galaxy with a smaller spiral galaxy a few hundred million years ago. As an indication of this, the spectacular band of dust that runs across the entire galaxy. In addition, in certain spectral regions, a "spiral structure can be detected in the core region. The collision and fusion triggered a violent star formation phase and, in addition, gas masses were deflected from their original orbits and partly collected around a black hole in the center. A black hole with the mass of 55 million solar masses is suspected in the centre. The active galactic core, which is hidden by this dust band, emits a large part of the high-energy radiation and also radio radiation. Centaurus A is also a powerful source of X-rays and gamma radiation.

Centaurus A's massive energy output comes from gas falling into the central black hole. Parts of these gas masses are ejected again from the black hole in two jets located opposite each other at a considerable part of the speed of light. The details of this process are still unclear. The jets interact with the surrounding gas and probably influence the star formation rate of the galaxy.

Centaurus A was discovered on August 4, 1826 by James Dunlop. He included the object in his "Catalogue of Nebulae and Clusters of Stars in the Southern Hemisphere observed in New South Wales". Centaurus A was classified as a strong radio galaxy in 1949 by John Bolton, Bruce Slee and Gordon Stanley.
« The image on the left shows a composite image of NGC 5128, which also shows the lobes and jets emanating from the galaxy's central black hole. The image shows data collected from three different instruments operating in different wavelength ranges. In orange are submillimeter data with a wavelength of 870 micrometers, which were recorded with the LABOCA camera on the APEX telescope. X-ray data from the Chandra satellite appear in blue. The images in visible light were taken by the Wide Field Imager (WFI) at the MPG/ESO 2.2-meter telescope on La Silla in Chile and show background stars and the dust band characteristic of this galaxy almost in true colors.

Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

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