* Astronomy

The Universe could have a fifth less mass than current estimates.
New studies, detailed in the Oct. 20 issue of Astrophysical Journal, indicate the universe contains 10 to 20 % less normal and dark matter than previously thought.


The grey scale is an R-band optical image of the cluster core taken at The Las Campanas Observatory. The overlayed contours represent the ROSAT HRI X-ray images which show the gas distribution within each of the clusters.
Credit LCO

The new weight estimate comes from new observations of the galaxy cluster Abell 3112.
In 2002, astronomers announced they had traced X-rays in the cluster to clouds of dust and gas between the galaxies. But surprisingly, new observations by the Chandra X-ray Observatory failed to detect the "spectral emission lines" given off by atoms in those clouds.
However, the scientists found that by adjusting the size of the power and normalisation they could make the distribution fit the spectrum of Abell 3112; the X-rays could be produced by lightweight electrons and photons colliding in space. This would change the total mass estimate of the cluster.

"This means the mass of these X-ray emitting clouds is much less than we initially thought it was" - Max Bonamente, astrophysicist at the University of Alabama in Huntsville.

The findings also affect the total dark matter in the galaxy cluster as there is less needed to hold the cluster together if there is less normal matter in Abell 3112.  Dark matter is still thought to be 5 times more plentiful than normal "baryonic" matter.