Thursday, February 24, 2011

As usual, favorites are rare

kw: astronomy, photographs, galaxies

I have a folder full of galaxy images as my current screen saver. Looking at it in a contemplative moment, I was struck again by how we prefer the big spirals to the much more common ellipticals. This image of M74 exemplifies what people think of as a galaxy:

By contrast, elliptical galaxies are simply bright blobs with a brighter center, and hardly any other features. This image of the center of cluster Abell SO740 is dominated by a very large elliptical galaxy. The large spiral to the lower left is probably a bit larger than our Milky Way galaxy, perhaps the size of the Andromeda galaxy (M31).

In this image, I can pick out two larger spirals and six or seven smaller ones which are probably part of a more distant cluster in the background. By contrast, there are dozens of elliptical galaxies of all sizes visible (again, many of these probably belong to a more distant cluster). Beauty may be in the eye of the beholder, and in this case, that eye seems to like a certain amount of detail and contrast. Compared to a richly detailed spiral galaxy, an elliptical galaxy is only slightly more interesting than a round, featureless spot.

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