The major "mass" is at Galaxy centre. It is considered at the centre of our Galaxy there is a major concentration of mass. However why there was the accumulation of mass and what the mechanism of this accumulation, it is not known.

Under Unified Theory of Nature at the centre of spiral galaxies there is "winding" of jets of ether, flowing in field of the centre of the galaxy. By that together with ether all particles and the bodies, (the particles and the bodies are pierced by ether see) which are in the field of fluxion of this ether move. The «winding» leads to the ether squeezing in the central region of a galaxy (The internal  pressure is increased see) and to its accumulation. Since the gravitational mass is the amount of the accumulated vortex ether, the gravitational mass of the galactic nucleus can be determined by expressing it in terms of the unit elementary mass (What is the gravitational mass? see) .

The shape of galaxies and their "massiveness". The up-to-date data of observations specifies the brightest and the most "massive" galaxies fall into to the types, close to the type Е О ([10] see). The causes of it have no the convincing explanations.

The brightness growth of galaxies streams from erected by the Unified Theory the increase of pressure in a kern of a galaxy ("The internal pressure is increased" see above)  in process of magnification of its age (The flat spiral, the ellipsoidal and the globe shapes of galaxies see). In process of transiting of phases of ageing of a galaxy the ether kern of the galaxy increases.  Respectively Inertia of the kern is growing (The essence of Inertia, consequence 2 see). Therefore there is the more and more intensive destruction of the smaller vortexes on the kern of the galaxy. This just is displayed in more and more  bright its luminescence.

Also under Unified Theory of Nature the least "massive" galaxies – the spiral, the most "massive" – the globe (Kinds of galaxies see). Accordingly a galaxy should transit still the long-term continuance of life for transmutation of the less "massive" spiral galaxy in the large "massive" globe (Classification of the types of galaxies see).