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Centaurus A

Hamburger Galaxy, C77, NGC 5128

Spanning the northern parts of the constellation Centaurus in the sky is a group of galaxies known as the Centaurus A/M83 Group after its two most important members. This group is a branch of the extensive Virgo Supercluster of galaxies, and is itself divided into two subgroups. At the heart of the southern subgroup, at a distance of a little over ten million light years from the Milky Way, lies the active galaxy known as Centaurus A.

Centaurus A is usually defined as lenticular in form, sharing characteristics with both elliptical galaxies and simple spirals, though its structure is highly unusual and there is some debate about its most appropriate classification. The main body of the galaxy appears elliptical in structure, but across this bright ellipse a dark band forms a wide and sinuous dust lane and defines a galactic plane. As seen from Earth, this dark stream appears to divide the main galaxy in two, giving rise to its occasionaly alternative name of the 'Hamburger Galaxy'.

It is generally thought that this unusual structure is the result of a collision in the galaxy's past, in which a large elliptical galaxy encountered and ultimately consumed a smaller spiral. The resulting deformations gave rise to a swarm of starburst regions, within which new stars have come into existence at a highly accelerated rate.

Perpendicular to the lane of material across the galactic plane, Centaurus A shows two distinct lobes extending outward into space in opposite directions. These lobes arise from jets of matter expelled by the immense black hole at the galaxy's heart. The lobes extend outward for thousands of light years into intergalactic space, and their emissions reach farther still, with detectable effects streaming millions of light years from the nucleus of the galaxy.

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