The dark lane is composed of dust and gas---basically the same thing as
nebulae. Within our own Milky Way, we're able to see some of them (the
Orion Nebula, Lagoon, Eagle, etc.) when newly formed hot stars are close
enough to excite the atoms in them. But there are many more that remain
dark and unilluminated.

Compare the image of NGC 891 with a wide field time exposure of the Milky
Way (like the one below) and you'll see a striking similarity. Dust lanes
are a feature of most edge-on spiral galaxies, but absent in ellipticals,
which tend to be dust poor.

http://www.davidmalin.com/fujii/source/af3-21_72.html




"G=EMC^2 Glazier" wrote in message
...
Have a picture of this galaxy(I like pictures) This galaxy shows itself
as a parrel plane in our line of view(horizontal) The picture is shown
in visible light. The first thought that comes to mind looking at the
picture is "what is that very dark area?" This dark area seems to slice
the galaxy into an upper and lower parts. It looks like a long black
cloud blocking out the stars that are in back of it. Would all galaxies
have this feature when their line of view is edge on ?
Bert