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 in a rotating system.  The Milky Way is "our" galaxy and it contains about 80 thousand million stars.  It has a spiral shape and rotates about its center once every 100 thousand years - so it's big!  Galaxies vary considerably in shape and size and although there are a lot of spiral galaxies like the Milky Way, there are also a lot of 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.  And there are yet other types which are partly or completely disorganized, some with tatty bits hanging off the side - these are known as Arps, after the astronomer who first discovered and catalogued them.

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 this 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 galaxy 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 as far as we can see 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 according to their nomenclature.  Click on the appropriate button to view them.

 

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