"Unexpected" - Hubble Reveals Something Missing in the Dark Universe

Sep 11, 2020


“One new theory says that dark matter may be ordinary matter in a parallel universe. If a galaxy is hovering above in another dimension, we would not be able to see it. It would be invisible, yet we would feel its gravity,”



“Something Missing” “With increasing distance, our knowledge fades, and fades rapidly. Eventually, we reach the dim boundary—the utmost limits of our telescopes. There, we measure shadows,” said astronomer Edwin Hubble, a quote that syncs perfectly with the image above captured by his namesake ... and the European Southern Observatory’s telescope in Chile that unveiled that something may be missing from the theories of how dark matter behaves in the massive galaxy cluster MACSJ 1206. Embedded within the cluster are the distorted images of distant background galaxies, seen as arcs and smeared features. These distortions are caused by the invisible dark matter in the cluster, whose gravity bends and magnifies the light from faraway galaxies ...

Gravitational lensing allows astronomers to study remote galaxy clusters, the most massive and recently assembled structures in the Universe, and the largest repositories of dark matter. Clusters are composed of individual member galaxies that are held together largely by the gravity of dark matter. Astronomers measured the amount of gravitational lensing caused by this cluster to produce a detailed map of the distribution of dark matter The new findings indicate that some small-scale concentrations of dark matter produce lensing effects that are 10 times stronger than expected... The higher the concentration of dark matter in a cluster, the more dramatic its light-bending effect. The presence of smaller-scale clumps of dark matter associated with individual cluster galaxies enhances the level of distortions. In some sense, the galaxy cluster acts as a large-scale lens that has many smaller lenses embedded within it.



To the team’s surprise, in addition to the dramatic arcs and elongated features of distant galaxies produced by each cluster’s gravitational lensing, the Hubble images also revealed an unexpected number of smaller-scale arcs and distorted images nested near each cluster’s core, where the most massive galaxies reside. The researchers believe the nested lenses are produced by the gravity of dense concentrations of matter inside the individual cluster galaxies... “We were able to associate the galaxies with each cluster and estimate their distances.” By combining Hubble imaging and VLT spectroscopy, the astronomers were able to identify dozens of multiply imaged, lensed, background galaxies. This allowed them to assemble a well-calibrated, high-resolution map of the mass distribution of dark matter in each cluster. “With high-resolution simulations, we can match the quality of observations analyzed in our paper, permitting detailed comparisons like never before ... Read more ...