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bicparker
Pooh-Bah
Reged: 02/07/05
Posts: 1438
Loc: Plano, TX
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Re: The vast "empty quarter" east of Sagittarius
07/28/08 11:58 AM
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Chris,
I set up the Tully 3D database of galaxies in Starry Night and "traveled in the direction of capicorn, et al and picked out a random galaxy in that region (this was actually more in the direction of Eridanus) and took a quick look at what I could tell from the relative density of that area.
First, there are a lot of galaxies there, but what you said about this being a product of a less dense filament of galaxies appears to be correct. It actually looks to be between filaments, which, while certainly less dense, isn't devoid of galaxies, either.
The accuracy of such 3D models is only so-so, though they do give a good statistical measure of relative densities. One also has to take into account that our accuracy is reduced as objects become more distant (heck, it is even hard to get a really accurate measure of things close to us!).
Probably, the fact that groups like the Virgo Cluster are simply closer also accounts, to some degree, how other areas may seem less dense. There are likely galaxies in these less denser areas that we can't see and they may obscured due to intergalactic medium. Since most of our observations are in the very narrow band of visible and near visible objects, we have a bit of a narrower perspective on what is around us. The Spitzer Space Telescope as well as other "out of visible range" instruments such as Chandra have already found several galaxies and other objects that were otherwise not visible in our normal optical spectrum.
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Bic Parker
17.5" f/5 dob
10" f/10 SCT
5" f/8 refractor
80mm f/6 refractor
66mm f/6 refractor
Plus a few others out of the rotation
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