From a distance it all looks pretty smooth, the same in every direction. The Cosmic Microwave Background is a barrier, beyond which we are unable to peer. It is also nearly as old as our universe and appears smooth -from a distance. The early universe was smooth, according to our current understanding. Today’s universe is, as cosmologists determined from what we understand of the early universe, lumpier. But not lumpy enough. Past observations show there appears to be some missing lumpiness. Did God do too good a job of making this gravy?
Maybe not. As usual, when we think we have discovered anomalies in the standard model, they tend to go away with more detailed inspection. This appears to be the case with our universe’s missing lumps.
Simulations of the early to current universe’s evolution predict the rise of a web-like or even foamy matrix that we should see on large scales. This matrix evolved, according to the simulations (based on theory), as ions and atoms formed, in turn forming molecular hydrogen. Molecules joined forces and evolved into larger and larger units … stars, galaxies. It’s galaxies that are supposed to have clustered and formed the web or foamy matrix that pervades our universe.
OK, this is all so big. It’s hard enough to try to visualize or even conceive of our Milky Way galaxy alone, much less dozens, hundreds, thousands of galaxies forming clusters strung together throughout the universe. We have known that galaxies cluster for some time, and that our Milky Way is part of a small local group, which in turn is part of the Virgo supercluster. That galaxy clusters and superclusters should be connected into long strands and filaments wasn’t considered until Soviet theorist Yakov Zeldovich proposed this concept in 1970. Since then, astronomers have been finding plenty of evidence for this matrix. The problem has been quantitative. There should be more web/bubble matrix than we can find.
Another problem, while intergalactic matter was believed to exist between and among galaxy clusters, we could not detect it, so had no way of knowing how much might be there.
We know dark matter is likely involved but how to identify that? Although we cannot see dark matter directly, we can observe its gravitational effect on visible matter. So, astronomers have taken the indirect approach to teasing out this invisible part of the universe’s matrix. They are using a tried-and-true process, gravitational lensing, to help spot the intergalactic filaments.
Instruments and techniques used to detect intergalactic matter include X-ray emission detection, and the Keck telescope Low Resolution Imaging Spectrometer in conjunction with Lyman-Alpha particle mapping from extremely distant galaxies. Additional observations using the Multi-Unit Spectroscopic Explorer (MUSE) show the glow of hydrogen gas fluorescence in these filaments. Put together these observations help identify the presence of faint filament structures, the missing lumpiness.
What’s in the Sky?
Keep looking in the west-southwest after sunset – for a planetary lineup – Jupiter, Saturn, Mercury too.