GALAXIES

Galaxies have been described as "island Universes" and once you realise what they are, you realise that this description is pretty accurate.  Galaxies are collections of millions and billions of stars, bound together gravitationally.  The Milky Way is "our" galaxy and it is a spiral galaxy containing about 80 thousand million stars, making one rotation about once every 100 thousand years.  Galaxies vary considerably in shape and size and although there are a lot of spiral galaxies like the Milky Way, there are many other types, some simply huge elliptical masses of stars, some small and poorly organized, and some with spectacular bars across the middle with arms attached to the ends of the bar.  There are yet other types which are partly or completely disorganized, some with sections seemingly hanging off the side.  One specific group of such galaxies was catalogued by an astronomer called Halton Arp, and they are therefore known as "Arp Galaxies.  Over the years we have managed to image all 338 of these objects and you can see these images on the Arp Galaxies page of this website.

Galaxies contain not only stars, but masses of dust and other material.  These dusty areas form the various "nebulae" which we can see in our own Milky Way system, and they are also visible in more remote galaxies.  If you look at the image of Messier 33 on the Messier Galaxies page you can see some of the nebulous areas in that galaxy.  Nebulae shine either by reflected light or by re-emitting energy which they have absorbed from stars embedded in them - see the Nebulae page on this web site.

Galaxies are all very distant from us.  The nearest large one to us is Messier 31 - the Andromeda Galaxy.  It is 2.5 million light years away, which means the light we are seeing started traveling towards us 2.5 million years ago.  Most galaxies are much farther away, and the further we look into deep space, using the largest telescopes in the world, the more galaxies we can see.  Here are some of the galaxies which we have imaged over the years.  There is a large number and so we have divided them up into groups (Messier, NGC [New General Catalogue] and Arp.  Click on the appropriate button to view them.