No. 110: Mar-Apr 1997
Cosmologists think in the large. Billions of stars are nothing to them. The megaparsec (3,528,000 light years) is but a hop, skip, and jump. A pressing question for these cosmologists searching for the really big picture is whether there is any order in the distribution of galaxies, galactic clusters, and superclusters. The scale of organization of the universe is of critical importance because it is a measure of state of the cosmos when hydrogen atoms first condensed from the seething sea of ions following the Big Bang. The prevailing expectation has been that galactic clusters and superclusters should be distributed at random; that is, no order prevails at that scale. Recent redshift measurements, however, hint more and more forcefully that the huge superclusters of galaxies are almost as neatly arranged as the atoms in a crystal.
A recent paper in Nature by J. Einasto et al puts a number on the spacing of the superclusters:
"Here, using a new compilation of available data on galaxy clusters, we present evidence for a quasi-regular three-dimensional network of rich superclusters and voids, with the regions of high density separated by "120 Mpc [megaparsecs]. If this reflects the distribution of all matter (luminous and dark), then there must exist some hitherto unknown process that produces regular structure on large scales."
(Einasto, J., et al; "A 120-Mpc Periodicity in the Three-Dimensional Distribution of Galaxy Superclusters," Nature, 385:139, 1997.)
Comment. Hmmm! A "hitherto unknown process." It appears that our science is still incomplete, despite what some science writers have insisted recently.
Reference. Chapter AWB in our catalog: Stars, Galaxies, Cosmos describes several other galaxy-distribution anomalies. For more on this book, visit here.