Using the largest survey of galaxies ever compiled, astronomers have found that the cosmos divides sharply along color lines. Old, red galaxies clump tightly, while young, blue ones are more spread out. Although the standard theory of galaxy formation predicts the same general trend, it permits a continuum, from very tight to very loose clustering. The survey, however, denies the middle ground.
There's no ready explanation for this great divide among galaxies, says Alex S. Szalay of Johns Hopkins University in Baltimore. His Johns Hopkins colleague Tams Budvari presented the findings this week at a meeting of the American Astronomical Society in Nashville.
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