What do galaxies have to do with cosmology?

                  Books   |   Astronomy Picture of the Day   |   News   |   Calendars   |   Star Charts   |   Observing   |   Education  

Galaxy Birth - Accompanying those minute fluctuations in radiation, scientists believe, were tiny fluctuations of matter, or, more precisely, baryonic matter, mainly hydrogen and helium gas. Gravitational attraction between the atoms concentrated them into faint clouds of gas. As the universe expanded, the surrounding matter gradually thinned out, with the result that the internal gravity of the gas clouds grew relatively stronger. Slowly, then faster and faster, the clouds pulled in more and more material from the surrounding medium. Eventually, the clouds began to collapse under their own gravity, evolving into galaxies. About one billion years after the Big Bang, the first galaxies and the stars they contain were born.

What happened to the searchable NGC database?
The Interactive NGC Catalog Online - This is the interactive NGC (and IC, and Messier) catalog at SEDS, based on the famous NGC 2000.0 by R.W. Sinnott of Sky Publishing Corp., who also created the electronic version used by this online service (thanks to Sky Publishing for permitting us this kind of use). Only some minor corrections have been included in our online database. The HTML interface and its features were created by Hartmut Frommert. Thanks to Bill Arnett for helpful hints and support, and the admins of SEDS who provided the appropriate hardware and software basis for this service.

Fix: Chapter 23 Galaxies Interactive Star Atlas
    Object Catalogues: Messier
    Object Catalogues: Deep Sky

Object name
Get coordinates from SIMBAD NED

Astronomy Picture of the Day: Galaxies - All the images on the APOD page are credited to the owner or institution where they originated. Some of the images are copyrighted and to use these pictures publicly or commercially one must write to the owners for permission. For the copyrighted images, the copyright owner is identified in the APOD credit line (please see the caption under the image), along with a hyperlink to the owner's location. NASA images are in the public domain, official guidelines for their use can be found here. For images credited to other owners/institutions, please contact them directly for copyright and permissions questions.

Atlas of the Andromeda Galaxy   by Paul W. Hodge
Atlas of Peculiar Galaxies   by Halton Arp
Catalogue of Southern Peculiar Galaxies & Associations   by Halton Arp et al

Galaxy Collisions - Theories of how galaxies, the fundamental constituents of large-scale structure, form and evolve have undergone a dramatic paradigm shift in the last few decades. Earlier views were of rapid, early collapse and formation of basic structures, followed by slow evolution of the stellar populations and steady buildup of the chemical elements. Current theories emphasize hierarchical buildup via recurrent collisions and mergers, separated by long periods of relaxation and secular restructuring. Thus, collisions between galaxies are now seen as a primary process in their evolution. This article begins with a brief history; we then tour parts of the vast array of collisional forms that have been discovered to date. Many examples are provided to illustrate how detailed numerical models and multiwaveband observations have allowed the general chronological sequence of collisional morphologies to be deciphered, and how these forms are produced by the processes of tidal kinematics, hypersonic gas dynamics, collective dynamical friction and violent relaxation. Galaxy collisions may trigger the formation of a large fraction of all the stars ever formed, and play a key role in fueling active galactic nuclei. Current understanding of the processes involved is reviewed. The last decade has seen exciting new discoveries about how collisions are orchestrated by their environment, how collisional processes depend on environment, and how these environments depend on redshift or cosmological time.

The Hubble Deep Field 1 2
Galaxies in the Young Universe
Galatic Structure, Globular Clusters
Classifying Galaxies -An Interactive Lesson on the Hubble System of Classifying Galaxies.

The Heart of the Milky Way
Explanation: Tuning in to the center of our Milky Way galaxy, radio astronomers explore a complex, mysterious place. A premier high resolution view, this startlingly beautiful picture covers a 4x4 degree region around the galactic center. It was constructed from 1 meter wavelength radio data obtained by telescopes of the Very Large Array near Socorro, New Mexico, USA. The galactic center itself is at the edge of the extremely bright object labeled Sagittarius (Sgr) A, suspected of harboring a million solar mass black hole. Along the galactic plane which runs diagonally through the image are tortured clouds of gas energized by hot stars and bubble-shaped supernova remnants (SNRs) - hallmarks of a violent and energetic cosmic environment. But perhaps most intriguing are the arcs, threads, and filaments which abound in the scene. Their uncertain origins challenge present theories of the dynamics of the galactic center.

Named Galaxies
Local Group galaxies



Copyright 2010 - Samuel J. Wormley