Island Worlds in Space and Time: Galaxies and Quasars

Abstract

The large size of the universe, combined with the finite speed of light, means that every glance into the depths of the universe is also a glance into the past. What is impossible for humans is no problem for the Hubble: to bring the past to life. However, very distant and therefore very old objects appear very small. The limited resolution of ground-based telescopes had always clouded our view of the distant past. Many questions have not yet been answered: How do galaxies evolve over billions of years? Is there a transition from spiral galaxies to elliptical galaxies, or the other way around? Does the number of galaxies decrease over time because of “cannibalism,” galaxies merging, or big galaxies pulling in little ones? Do new galaxies condense out of hitherto “unused” hydrogen and helium in the universe? Hubble is in the process of providing important information to clarify these questions.