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.
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
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 2007 - Samuel J. Wormley
by swormley1@mchsi.com
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