Origin of Stars and Galaxies

Abstract

A galaxy is produced by a collision between two portions of raw material moving under their mutual gravitation;shocked material produces primary condensations in which short-lived exploding massive stars produce the first heavy elements; a condensation then becomes a globular cluster of the first normal stars, the entire galaxy being thus initially a “cluster” of such clusters; tidal dissipation — and possibly other effects to be mentioned — converts most of these into a halo stellar population; subsequent evolution depends upon whether residual diffuse material falls mainly into a disk or into a nucleus (or perhaps expands into a larger halo).