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Forty years later, the American astronomer Edward Fath revisited the question of Abbe. After measuring the orientations of hundreds of galaxies on photographic plates taken at the Mount Wilson Observatory, he stated in 1914 that they "seemed to be randomly oriented".
Decades of lively debate followed. The English amateur astronomer Francis Brown spent more than 30 years studying galaxy alignments during his free time. In a series of articles published between 1938 and 1968, he presented evidence that the directions of galaxies in certain regions of the sky were far from random. But many astronomers remained skeptical, suggesting that the results could be a consequence of measurement errors, selection effects, or even psychological bias.
Most galaxies have an elongated shape; rounds are rare. But why?
The image of a galaxy is a snapshot of the movements of its stars, a moment frozen in time. Spiral galaxies like the Milky Way owe their flattened shapes to rotation. Just as a ball of pizza dough flattens when it is spun, the stars of a spiral galaxy spread out into a spinning disc. Traveling half a million kilometers an hour, our Sun has made nearly two dozen trips around the Milky Way since birth.
Elliptical galaxies, on the other hand, have little or no rotation. Their stars swarm around the center of the galaxy like bees around a hive, each following its own seemingly random path. However, these orbits are often longer than the others in one direction, which gives the galaxy a shape similar to that of a luminescent football. – M.W.
Then, in 1968, Gummuluru Sastry of Wesleyan University proved beyond doubt that the orientations of certain galaxies are clearly not random. Sastry discovered that the giant elliptical galaxies that populate the cluster centers – the largest and brightest galaxies in the universe – have a remarkable tendency to extend in the same direction as their host cluster. For example, if a group is lying north-south, its brightest member galaxy is the most often. If galaxies were human beings, psychologists would call it a classic example of mirror behavior.
Although Sastry's conclusion is based on only five galaxies, other astronomers have subsequently confirmed their results with much larger samples. Recent studies done with the Hubble Space Telescope – whose clear vision allows us to see the distant past looking far into space – reveal that these alignments existed even billions of years ago.
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