Free Astronomy Magazine March-April 2016

27 GALACTIC EVOLUTION compatible either with the observational reality or with mathematical models’ pre- dictions. If instead the nu- clear disks were at least in most cases made up of stars younger than those of the spheroid (the central bulge of a galaxy), by being able to precisely calculate their age would not only defi- nitely exclude the alterna- tive scenario, but also es- tablish the era to which the last merger of a given gal- axy could be traced back. Doing this for a significant sample of galaxies would allow refining our know- ledge of the evolutionary history on large-scale of these structures. This kind of investigation appears how- ever, rather difficult, since the small apparent size of the nuclear disks will allow an in-depth study of them A section of Markarian's Chain, to which belongs NGC 4458, distinguishable by its spherical shape in the top part of the image. [Wikisky SDSS7]