Black-hole brains of NGC 3109, The

A civilisation in the Local Group of galaxies that lives in close association with black holes

Black Hole Brain
Image from Steve Bowers
Although the black holes themselves are invisible at this distance, the megastructures which surround them can be clearly seen with the Argus Array

At the edge of the Local Group of galaxies, NGC 3109 is a small irregular galaxy 4.2 million light years from the Terragen Sphere. In the past, this galaxy was a small barred spiral, similar to the Large Magellanic Cloud, but it has been disrupted in the relatively recent past through interaction with a galaxy in the nearby Antilia group, a small association of galaxies outside the Local Group itself.

Arranged in an arc around the centre of this galaxy are several thousand systems that include large megastructures of a distinct type, which have been constructed by an unknown xenosophont civilisation. Each structure is around a thousand kilometres across (though some are much larger), and consists of a disk of independently rotating rings, which often display patterns that are near the limit of resolution at this distance. At the centre of the disk is a small, massive object which is consistent with a black hole of planetary mass - the largest of these objects are as massive as a Y-type brown dwarf, but none are massive enough to have formed naturally via stellar collapse. The average radius of the black holes in these objects is around two metres.

In each of these systems there is often a medium-sized terrestrial planet, most of which show signs of habitation. The inhabitants of these worlds (which are too small to be seen clearly) seem to conform to several different types, each with different environmental needs. Since these worlds are more than twice as far away as the Andromeda Galaxy, it is not possible to determine if the inhabitants of these worlds share a common origin; they appear as no more than indistinct blobs at this range. On occasion, indistinct shadows can be seen at the planet's terminator which may be individual xenosophonts from this civilisation, or possibly their robotic servants, or statues they have erected of themselves (or their gods or demons). These shadows consistently appear to have six legs. Several of these worlds are abandoned, and some appear to have been reinhabited after a long period of desolation; a few show signs of warfare.

The black-hole disc megastructures are believed to have been optimised for processing information, becoming in effect 'black-hole brains'. Although the exact process used by this distant civilisation is not known in detail, there are many theoretical ways that a black hole and/or the space just above its event horizon can be used for computation. Small amounts of stray gamma-ray emission from some of these objects suggest that the process used is photonic in nature, but this may not be the case.

Black-hole brains have rarely been constructed in the Terragen Sphere, perhaps because the development of wormhole-brains has made them unnecessary, but it seems to be the favoured method used in this culture. Since the worlds associated with these objects show some evidence of long occupation, it seems likely that the civilisation in this location is old and conservative.

Some commentators suggest that the bulk of this civilisation has already migrated into the black holes, and will remain there until these objects eventually evaporate in the far distant future; due to time dilation, the inside of a black hole experiences rapidly accelerated time compared to the rest of the universe, but the inhabitants would also receive a very large amount of infalling information and data, allowing them to attain a state comparable to a miniature omega-point civilisation.

Other observers think that they are simply waiting for the universe to cool down and make the process of computation more efficient. By hovering just above the event horizon these xenosophonts could reduce the waiting time considerably.

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Text by Steve Bowers
Initially published on 09 August 2018.