Is the Great Wall the largest galaxy cluster?
I could not find a picture of the Great Wall galaxy cluster on your site and was wondering if it was the largest galaxy cluster ever recorded. If you could send a picture of it and a ranking of its largeness that would be highly helpful. Thank you for taking the time to read this.
The Great Wall isn't a cluster. It's a feature that shows up on the Center for Astrophysics (CfA) Redshift Survey as an "overdensity" of galaxies. In this picture, each point of light represents a galaxy, and the Great Wall is the roughly horizontal band that stretches across the northern (top) part of the survey. The "wall" is more than 200 million light-years away, and stretches across roughly 600 million light-years from end to end (*much* bigger than clusters). But does that mean that galaxies are actually clustering on scales larger than superclusters? Not exactly. The CfA Redshift Survey consists of two slices of the sky that are each 36 degrees thick. Because the slice in the northern sky happens to be chose so that it intersects with several superclusters in a row, the "wall" shows up much more prominently than if the slice were oriented differently. Also, there's a geometric effect at work in the "cone diagram" plots that the Great Wall is typically presented in, which artificially boosts the apparent density of galaxies at the distance of the Great Wall. Considering these effects together, the Great Wall isn't quite as great.
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