The uncertainty of science: Using data from two space telescopes, astronomers have found that the universe’s expansion rate appears to differ depending on the direction you look.
This latest test uses a powerful, novel and independent technique. It capitalizes on the relationship between the temperature of the hot gas pervading a galaxy cluster and the amount of X-rays it produces, known as the cluster’s X-ray luminosity. The higher the temperature of the gas in a cluster, the higher the X-ray luminosity is. Once the temperature of the cluster gas is measured, the X-ray luminosity can be estimated. This method is independent of cosmological quantities, including the expansion speed of the universe.
Once they estimated the X-ray luminosities of their clusters using this technique, scientists then calculated luminosities using a different method that does depend on cosmological quantities, including the universe’s expansion speed. The results gave the researchers apparent expansion speeds across the whole sky — revealing that the universe appears to be moving away from us faster in some directions than others.
The team also compared this work with studies from other groups that have found indications of a lack of isotropy using different techniques. They found good agreement on the direction of the lowest expansion rate.
The other research mentioned in the last paragraph in the quote above describes results posted here in December. For some reason that research did not get the publicity of today’s research, possibly because it had not yet been confirmed by others. It now has.
What this research tells us, most of all, is that dark energy, the mysterious force that is theorized to cause the universe’s expansion rate to accelerate — not slow down as you would expect– might not exist.
Update: I’ve decided to embed, below the fold, the very clear explanatory video made by one of the scientists doing that other research. Very helpful in explaining this very knotty science.